v0.5.0

[ci skip] Update readme
Change Client APIs
2025-09-17 20:30:06 +08:00 · 2020-02-23 20:44:44 -08:00 · 2020-02-23 20:44:44 -08:00 · 2020-02-23 20:40:40 -08:00 · 2020-02-22 21:21:55 -08:00 · 2020-02-22 21:21:55 -08:00
38 changed files with 2413 additions and 970 deletions
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,7 +5,10 @@ git:
 env:
  - GO111MODULE=on # go modules are the default
 go: [1.12.x, 1.13.x]
+script:
+  - go test -race -v -coverprofile=coverage.txt -covermode=atomic ./...
 services:
  - redis-server
 after_success:
  - bash ./.travis/benchcmp.sh
+  - bash <(curl -s https://codecov.io/bash)
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,28 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

 ## [Unreleased]

+## [0.5.0] - 2020-02-23
+
+### Changed
+
+- `Client` API has changed. Use `Enqueue`, `EnqueueAt` and `EnqueueIn` to enqueue and schedule tasks.
+
+### Added
+
+- `asynqmon workers` was added to list all running workers information
+
+## [0.4.0] - 2020-02-13
+
+### Changed
+
+- `Handler` interface has changed. `ProcessTask` method takes two arguments `context.Context` and `*asynq.Task`
+- `Queues` field in `Config` has change from `map[string]uint` to `map[string]int`
+
+### Added
+
+- `Client` can optionally schedule task with `asynq.Timeout(duration)` to specify timeout duration for task. Default is no timeout.
+- `asynqmon cancel [task id]` will send a cancelation signal to the goroutine processing the speicified task.
+
 ## [0.3.0] - 2020-02-04

 ### Added
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -0,0 +1,51 @@
+# Contributing
+
+Thanks for your interest in contributing to Asynq!
+We are open to, and grateful for, any contributions made by the community.
+
+## Reporting Bugs
+
+Have a look at our [issue tracker](https://github.com/hibiken/asynq/issues). If you can't find an issue (open or closed)
+describing your problem (or a very similar one) there, please open a new issue with
+the following details:
+
+- Which versions of Go and Redis are you using?
+- What are you trying to accomplish?
+- What is the full error you are seeing?
+- How can we reproduce this?
+  - Please quote as much of your code as needed to reproduce (best link to a
+    public repository or Gist)
+
+## Getting Help
+
+We run a [Gitter
+channel](https://gitter.im/go-asynq/community) where you can ask questions and
+get help. Feel free to ask there before opening a GitHub issue.
+
+## Submitting Feature Requests
+
+If you can't find an issue (open or closed) describing your idea on our [issue
+tracker](https://github.com/hibiken/asynq/issues), open an issue. Adding answers to the following
+questions in your description is +1:
+
+- What do you want to do, and how do you expect Asynq to support you with that?
+- How might this be added to Asynq?
+- What are possible alternatives?
+- Are there any disadvantages?
+
+Thank you! We'll try to respond as quickly as possible.
+
+## Contributing Code
+
+1. Fork this repo
+2. Download your fork `git clone https://github.com/your-username/asynq && cd asynq`
+3. Create your branch `git checkout -b your-branch-name`
+4. Make and commit your changes
+5. Push the branch `git push origin your-branch-name`
+6. Create a new pull request
+
+Please try to keep your pull request focused in scope and avoid including unrelated commits.
+
+After you have submitted your pull request, we'll try to get back to you as soon as possible. We may suggest some changes or improvements.
+
+Thank you for contributing!
--- a/README.md
+++ b/README.md
@@ -5,6 +5,7 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/hibiken/asynq)](https://goreportcard.com/report/github.com/hibiken/asynq)
 [![GoDoc](https://godoc.org/github.com/hibiken/asynq?status.svg)](https://godoc.org/github.com/hibiken/asynq)
 [![Gitter chat](https://badges.gitter.im/go-asynq/gitter.svg)](https://gitter.im/go-asynq/community)
+[![codecov](https://codecov.io/gh/hibiken/asynq/branch/master/graph/badge.svg)](https://codecov.io/gh/hibiken/asynq)

 Asynq is a simple Go library for queueing tasks and processing them in the background with workers.  
 It is backed by Redis and it is designed to have a low barrier to entry. It should be integrated in your web stack easily.
@@ -21,12 +22,12 @@ To install `asynq` library, run the following command:
 go get -u github.com/hibiken/asynq
 ```

-## Quick Start
+## Quickstart

 First, make sure you are running a Redis server locally.

 ```sh
-redis-server
+$ redis-server
 ```

 To create and schedule tasks, use `Client` and provide a task and when to process the task.
@@ -34,7 +35,7 @@ To create and schedule tasks, use `Client` and provide a task and when to proces
 ```go
 func main() {
    r := &asynq.RedisClientOpt{
-        Addr: "localhost:6379",
+        Addr: "127.0.0.1:6379",
    }

    client := asynq.NewClient(r)
@@ -45,16 +46,21 @@ func main() {
    t2 := asynq.NewTask("send_reminder_email", map[string]interface{}{"user_id": 42})

    // Process immediately
-    err := client.Schedule(t1, time.Now())
+    err := client.Enqueue(t1)

    // Process 24 hrs later
-    err = client.Schedule(t2, time.Now().Add(24 * time.Hour))
+    err = client.EnqueueIn(24*time.Hour, t2)

-    // If processing fails, retry up to 10 times (Default is 25)
-    err = client.Schedule(t1, time.Now(), asynq.Retry(10))
+    // Process at specified time.
+    t := time.Date(2020, time.March, 6, 10, 0, 0, 0, time.UTC)
+    err = client.EnqueueAt(t, t2)

-    // Use custom queue called "critical"
-    err = client.Schedule(t1, time.Now(), asynq.Queue("critical"))
+    // Pass options to specify processing behavior for a given task.
+    //
+    // MaxRetry specifies the maximum number of times this task will be retried (Default is 25).
+    // Queue specifies which queue to enqueue this task to (Default is "default").
+    // Timeout specifies the the timeout for the task's context (Default is no timeout).
+    err = client.Enqueue(t1, asynq.MaxRetry(10), asynq.Queue("critical"), asynq.Timeout(time.Minute))
 }
 ```

@@ -63,15 +69,14 @@ To start the background workers, use `Background` and provide your `Handler` to
 ```go
 func main() {
    r := &asynq.RedisClientOpt{
-        Addr: "localhost:6379",
+        Addr: "127.0.0.1:6379",
    }

    bg := asynq.NewBackground(r, &asynq.Config{
        // Specify how many concurrent workers to use
        Concurrency: 10,
-        // You can optionally create multiple queues
-        // with different priority level
-        Queues: map[string]uint{
+        // Optionally specify multiple queues with different priority.
+        Queues: map[string]int{
            "critical": 6,
            "default":  3,
            "low":      1,
@@ -92,7 +97,7 @@ func main() {
 // If ProcessTask return a non-nil error or panics, the task
 // will be retried after delay.
 type Handler interface {
-    ProcessTask(*Task) error
+    ProcessTask(context.Context, *asynq.Task) error
 }
 ```

@@ -113,13 +118,21 @@ Asynq ships with a command line tool to inspect the state of queues and tasks.

 To install, run the following command:

-    go get github.com/hibiken/asynq/tools/asynqmon
+```sh
+go get -u github.com/hibiken/asynq/tools/asynqmon
+```

 For details on how to use the tool, refer to the tool's [README](/tools/asynqmon/README.md).

+## Contributing
+
+We are open to, and grateful for, any contributions (Github issues/pull-requests, feedback on Gitter channel, etc) made by the community.
+Please see the [Contribution Guide](/CONTRIBUTING.md) before contributing.
+
 ## Acknowledgements

 - [Sidekiq](https://github.com/mperham/sidekiq) : Many of the design ideas are taken from sidekiq and its Web UI
+- [RQ](https://github.com/rq/rq) : Client APIs are inspired by rq library.
 - [Cobra](https://github.com/spf13/cobra) : Asynqmon CLI is built with cobra

 ## License
--- a/asynq.go
+++ b/asynq.go
@@ -11,7 +11,7 @@ import (
 	"github.com/go-redis/redis/v7"
 )

-// Task represents a task to be performed.
+// Task represents a unit of work to be performed.
 type Task struct {
 	// Type indicates the type of task to be performed.
 	Type string
@@ -20,10 +20,9 @@ type Task struct {
 	Payload Payload
 }

-// NewTask returns a new Task. The typename and payload argument set Type
-// and Payload field respectively.
+// NewTask returns a new Task given a type name and payload data.
 //
-// The payload must be serializable to JSON.
+// The payload values must be serializable.
 func NewTask(typename string, payload map[string]interface{}) *Task {
 	return &Task{
 		Type:    typename,
@@ -31,13 +30,11 @@ func NewTask(typename string, payload map[string]interface{}) *Task {
 	}
 }

-// RedisConnOpt is a discriminated union of redis-client-option types.
+// RedisConnOpt is a discriminated union of types that represent Redis connection configuration option.
 //
 // RedisConnOpt represents a sum of following types:
 //
 // RedisClientOpt | *RedisClientOpt | RedisFailoverClientOpt | *RedisFailoverClientOpt
-//
-// Passing unexpected type to a RedisConnOpt variable can cause panic.
 type RedisConnOpt interface{}

 // RedisClientOpt is used to create a redis client that connects
@@ -53,7 +50,7 @@ type RedisClientOpt struct {
 	// Redis server password.
 	Password string

-	// Redis DB to select after connecting to the server.
+	// Redis DB to select after connecting to a server.
 	// See: https://redis.io/commands/select.
 	DB int

@@ -61,13 +58,13 @@ type RedisClientOpt struct {
 	// Default is 10 connections per every CPU as reported by runtime.NumCPU.
 	PoolSize int

-	// TLS Config used to connect to the server.
+	// TLS Config used to connect to a server.
 	// TLS will be negotiated only if this field is set.
 	TLSConfig *tls.Config
 }

 // RedisFailoverClientOpt is used to creates a redis client that talks
-// to redis sentinels for service discovery and has automatic failover
+// to redis sentinels for service discovery and has an automatic failover
 // capability.
 type RedisFailoverClientOpt struct {
 	// Redis master name that monitored by sentinels.
@@ -84,7 +81,7 @@ type RedisFailoverClientOpt struct {
 	// Redis server password.
 	Password string

-	// Redis DB to select after connecting to the server.
+	// Redis DB to select after connecting to a server.
 	// See: https://redis.io/commands/select.
 	DB int

@@ -92,11 +89,14 @@ type RedisFailoverClientOpt struct {
 	// Default is 10 connections per every CPU as reported by runtime.NumCPU.
 	PoolSize int

-	// TLS Config used to connect to the server.
+	// TLS Config used to connect to a server.
 	// TLS will be negotiated only if this field is set.
 	TLSConfig *tls.Config
 }

+// createRedisClient returns a redis client given a redis connection configuration.
+//
+// Passing an unexpected type as a RedisConnOpt argument will cause panic.
 func createRedisClient(r RedisConnOpt) *redis.Client {
 	switch r := r.(type) {
 	case *RedisClientOpt:
--- a/background.go
+++ b/background.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"context"
 	"fmt"
 	"math"
 	"math/rand"
@@ -33,19 +34,24 @@ type Background struct {
 	mu      sync.Mutex
 	running bool

-	pinfo       *base.ProcessInfo
+	ps *base.ProcessState
+
+	// wait group to wait for all goroutines to finish.
+	wg sync.WaitGroup
+
 	rdb         *rdb.RDB
 	scheduler   *scheduler
 	processor   *processor
 	syncer      *syncer
 	heartbeater *heartbeater
+	subscriber  *subscriber
 }

 // Config specifies the background-task processing behavior.
 type Config struct {
 	// Maximum number of concurrent processing of tasks.
 	//
-	// If set to zero or negative value, NewBackground will overwrite the value to one.
+	// If set to a zero or negative value, NewBackground will overwrite the value to one.
 	Concurrency int

 	// Function to calculate retry delay for a failed task.
@@ -57,15 +63,15 @@ type Config struct {
 	// t is the task in question.
 	RetryDelayFunc func(n int, e error, t *Task) time.Duration

-	// List of queues to process with given priority level. Keys are the names of the
-	// queues and values are associated priority level.
+	// List of queues to process with given priority value. Keys are the names of the
+	// queues and values are associated priority value.
 	//
 	// If set to nil or not specified, the background will process only the "default" queue.
 	//
 	// Priority is treated as follows to avoid starving low priority queues.
 	//
 	// Example:
-	// Queues: map[string]uint{
+	// Queues: map[string]int{
 	//     "critical": 6,
 	//     "default":  3,
 	//     "low":      1,
@@ -73,7 +79,9 @@ type Config struct {
 	// With the above config and given that all queues are not empty, the tasks
 	// in "critical", "default", "low" should be processed 60%, 30%, 10% of
 	// the time respectively.
-	Queues map[string]uint
+	//
+	// If a queue has a zero or negative priority value, the queue will be ignored.
+	Queues map[string]int

 	// StrictPriority indicates whether the queue priority should be treated strictly.
 	//
@@ -90,7 +98,7 @@ func defaultDelayFunc(n int, e error, t *Task) time.Duration {
 	return time.Duration(s) * time.Second
 }

-var defaultQueueConfig = map[string]uint{
+var defaultQueueConfig = map[string]int{
 	base.DefaultQueueName: 1,
 }

@@ -105,8 +113,13 @@ func NewBackground(r RedisConnOpt, cfg *Config) *Background {
 	if delayFunc == nil {
 		delayFunc = defaultDelayFunc
 	}
-	queues := cfg.Queues
-	if queues == nil || len(queues) == 0 {
+	queues := make(map[string]int)
+	for qname, p := range cfg.Queues {
+		if p > 0 {
+			queues[qname] = p
+		}
+	}
+	if len(queues) == 0 {
 		queues = defaultQueueConfig
 	}

@@ -116,20 +129,23 @@ func NewBackground(r RedisConnOpt, cfg *Config) *Background {
 	}
 	pid := os.Getpid()

-	pinfo := base.NewProcessInfo(host, pid, n, queues, cfg.StrictPriority)
 	rdb := rdb.NewRDB(createRedisClient(r))
-	syncRequestCh := make(chan *syncRequest)
-	syncer := newSyncer(syncRequestCh, 5*time.Second)
-	heartbeater := newHeartbeater(rdb, pinfo, 5*time.Second)
+	ps := base.NewProcessState(host, pid, n, queues, cfg.StrictPriority)
+	syncCh := make(chan *syncRequest)
+	cancels := base.NewCancelations()
+	syncer := newSyncer(syncCh, 5*time.Second)
+	heartbeater := newHeartbeater(rdb, ps, 5*time.Second)
 	scheduler := newScheduler(rdb, 5*time.Second, queues)
-	processor := newProcessor(rdb, pinfo, delayFunc, syncRequestCh)
+	processor := newProcessor(rdb, ps, delayFunc, syncCh, cancels)
+	subscriber := newSubscriber(rdb, cancels)
 	return &Background{
-		pinfo:       pinfo,
 		rdb:         rdb,
+		ps:          ps,
 		scheduler:   scheduler,
 		processor:   processor,
 		syncer:      syncer,
 		heartbeater: heartbeater,
+		subscriber:  subscriber,
 	}
 }

@@ -141,18 +157,18 @@ func NewBackground(r RedisConnOpt, cfg *Config) *Background {
 // If ProcessTask return a non-nil error or panics, the task
 // will be retried after delay.
 type Handler interface {
-	ProcessTask(*Task) error
+	ProcessTask(context.Context, *Task) error
 }

 // The HandlerFunc type is an adapter to allow the use of
 // ordinary functions as a Handler. If f is a function
 // with the appropriate signature, HandlerFunc(f) is a
 // Handler that calls f.
-type HandlerFunc func(*Task) error
+type HandlerFunc func(context.Context, *Task) error

-// ProcessTask calls fn(task)
-func (fn HandlerFunc) ProcessTask(task *Task) error {
-	return fn(task)
+// ProcessTask calls fn(ctx, task)
+func (fn HandlerFunc) ProcessTask(ctx context.Context, task *Task) error {
+	return fn(ctx, task)
 }

 // Run starts the background-task processing and blocks until
@@ -176,7 +192,7 @@ func (bg *Background) Run(handler Handler) {
 		sig := <-sigs
 		if sig == syscall.SIGTSTP {
 			bg.processor.stop()
-			bg.pinfo.SetState("stopped")
+			bg.ps.SetStatus(base.StatusStopped)
 			continue
 		}
 		break
@@ -196,10 +212,11 @@ func (bg *Background) start(handler Handler) {
 	bg.running = true
 	bg.processor.handler = handler

-	bg.heartbeater.start()
-	bg.syncer.start()
-	bg.scheduler.start()
-	bg.processor.start()
+	bg.heartbeater.start(&bg.wg)
+	bg.subscriber.start(&bg.wg)
+	bg.syncer.start(&bg.wg)
+	bg.scheduler.start(&bg.wg)
+	bg.processor.start(&bg.wg)
 }

 // stops the background-task processing.
@@ -210,16 +227,19 @@ func (bg *Background) stop() {
 		return
 	}

+	// Note: The order of termination is important.
+	// Sender goroutines should be terminated before the receiver goroutines.
+	//
+	// processor -> syncer (via syncCh)
 	bg.scheduler.terminate()
 	bg.processor.terminate()
-	// Note: processor and all worker goroutines need to be exited
-	// before shutting down syncer to avoid goroutine leak.
 	bg.syncer.terminate()
+	bg.subscriber.terminate()
 	bg.heartbeater.terminate()

-	bg.rdb.ClearProcessInfo(bg.pinfo)
+	bg.wg.Wait()
+
 	bg.rdb.Close()
-	bg.processor.handler = nil
 	bg.running = false

 	logger.info("Bye!")
--- a/background_test.go
+++ b/background_test.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"context"
 	"testing"
 	"time"

@@ -27,31 +28,37 @@ func TestBackground(t *testing.T) {
 	})

 	// no-op handler
-	h := func(task *Task) error {
+	h := func(ctx context.Context, task *Task) error {
 		return nil
 	}

 	bg.start(HandlerFunc(h))

-	client.Schedule(NewTask("send_email", map[string]interface{}{"recipient_id": 123}), time.Now())
+	err := client.Enqueue(NewTask("send_email", map[string]interface{}{"recipient_id": 123}))
+	if err != nil {
+		t.Errorf("could not enqueue a task: %v", err)
+	}

-	client.Schedule(NewTask("send_email", map[string]interface{}{"recipient_id": 456}), time.Now().Add(time.Hour))
+	err = client.EnqueueAt(time.Now().Add(time.Hour), NewTask("send_email", map[string]interface{}{"recipient_id": 456}))
+	if err != nil {
+		t.Errorf("could not enqueue a task: %v", err)
+	}

 	bg.stop()
 }

 func TestGCD(t *testing.T) {
 	tests := []struct {
-		input []uint
-		want  uint
+		input []int
+		want  int
 	}{
-		{[]uint{6, 2, 12}, 2},
-		{[]uint{3, 3, 3}, 3},
-		{[]uint{6, 3, 1}, 1},
-		{[]uint{1}, 1},
-		{[]uint{1, 0, 2}, 1},
-		{[]uint{8, 0, 4}, 4},
-		{[]uint{9, 12, 18, 30}, 3},
+		{[]int{6, 2, 12}, 2},
+		{[]int{3, 3, 3}, 3},
+		{[]int{6, 3, 1}, 1},
+		{[]int{1}, 1},
+		{[]int{1, 0, 2}, 1},
+		{[]int{8, 0, 4}, 4},
+		{[]int{9, 12, 18, 30}, 3},
 	}

 	for _, tc := range tests {
@@ -64,46 +71,46 @@ func TestGCD(t *testing.T) {

 func TestNormalizeQueueCfg(t *testing.T) {
 	tests := []struct {
-		input map[string]uint
-		want  map[string]uint
+		input map[string]int
+		want  map[string]int
 	}{
 		{
-			input: map[string]uint{
+			input: map[string]int{
 				"high":    100,
 				"default": 20,
 				"low":     5,
 			},
-			want: map[string]uint{
+			want: map[string]int{
 				"high":    20,
 				"default": 4,
 				"low":     1,
 			},
 		},
 		{
-			input: map[string]uint{
+			input: map[string]int{
 				"default": 10,
 			},
-			want: map[string]uint{
+			want: map[string]int{
 				"default": 1,
 			},
 		},
 		{
-			input: map[string]uint{
+			input: map[string]int{
 				"critical": 5,
 				"default":  1,
 			},
-			want: map[string]uint{
+			want: map[string]int{
 				"critical": 5,
 				"default":  1,
 			},
 		},
 		{
-			input: map[string]uint{
+			input: map[string]int{
 				"critical": 6,
 				"default":  3,
 				"low":      0,
 			},
-			want: map[string]uint{
+			want: map[string]int{
 				"critical": 2,
 				"default":  1,
 				"low":      0,
--- a/benchmark_test.go
+++ b/benchmark_test.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"context"
 	"fmt"
 	"math/rand"
 	"sync"
@@ -12,8 +13,7 @@ import (
 	"time"
 )

-// Simple E2E Benchmark testing with no scheduled tasks and
-// no retries.
+// Simple E2E Benchmark testing with no scheduled tasks and retries.
 func BenchmarkEndToEndSimple(b *testing.B) {
 	const count = 100000
 	for n := 0; n < b.N; n++ {
@@ -33,12 +33,14 @@ func BenchmarkEndToEndSimple(b *testing.B) {
 		// Create a bunch of tasks
 		for i := 0; i < count; i++ {
 			t := NewTask(fmt.Sprintf("task%d", i), map[string]interface{}{"data": i})
-			client.Schedule(t, time.Now())
+			if err := client.Enqueue(t); err != nil {
+				b.Fatalf("could not enqueue a task: %v", err)
+			}
 		}

 		var wg sync.WaitGroup
 		wg.Add(count)
-		handler := func(t *Task) error {
+		handler := func(ctx context.Context, t *Task) error {
 			wg.Done()
 			return nil
 		}
@@ -74,16 +76,20 @@ func BenchmarkEndToEnd(b *testing.B) {
 		// Create a bunch of tasks
 		for i := 0; i < count; i++ {
 			t := NewTask(fmt.Sprintf("task%d", i), map[string]interface{}{"data": i})
-			client.Schedule(t, time.Now())
+			if err := client.Enqueue(t); err != nil {
+				b.Fatalf("could not enqueue a task: %v", err)
+			}
 		}
 		for i := 0; i < count; i++ {
 			t := NewTask(fmt.Sprintf("scheduled%d", i), map[string]interface{}{"data": i})
-			client.Schedule(t, time.Now().Add(time.Second))
+			if err := client.EnqueueAt(time.Now().Add(time.Second), t); err != nil {
+				b.Fatalf("could not enqueue a task: %v", err)
+			}
 		}

 		var wg sync.WaitGroup
 		wg.Add(count * 2)
-		handler := func(t *Task) error {
+		handler := func(ctx context.Context, t *Task) error {
 			// randomly fail 1% of tasks
 			if rand.Intn(100) == 1 {
 				return fmt.Errorf(":(")
@@ -101,3 +107,64 @@ func BenchmarkEndToEnd(b *testing.B) {
 		b.StartTimer() // end teardown
 	}
 }
+
+// Simple E2E Benchmark testing with no scheduled tasks and retries with multiple queues.
+func BenchmarkEndToEndMultipleQueues(b *testing.B) {
+	// number of tasks to create for each queue
+	const (
+		highCount    = 20000
+		defaultCount = 20000
+		lowCount     = 20000
+	)
+	for n := 0; n < b.N; n++ {
+		b.StopTimer() // begin setup
+		setup(b)
+		redis := &RedisClientOpt{
+			Addr: redisAddr,
+			DB:   redisDB,
+		}
+		client := NewClient(redis)
+		bg := NewBackground(redis, &Config{
+			Concurrency: 10,
+			Queues: map[string]int{
+				"high":    6,
+				"default": 3,
+				"low":     1,
+			},
+		})
+		// Create a bunch of tasks
+		for i := 0; i < highCount; i++ {
+			t := NewTask(fmt.Sprintf("task%d", i), map[string]interface{}{"data": i})
+			if err := client.Enqueue(t, Queue("high")); err != nil {
+				b.Fatalf("could not enqueue a task: %v", err)
+			}
+		}
+		for i := 0; i < defaultCount; i++ {
+			t := NewTask(fmt.Sprintf("task%d", i), map[string]interface{}{"data": i})
+			if err := client.Enqueue(t); err != nil {
+				b.Fatalf("could not enqueue a task: %v", err)
+			}
+		}
+		for i := 0; i < lowCount; i++ {
+			t := NewTask(fmt.Sprintf("task%d", i), map[string]interface{}{"data": i})
+			if err := client.Enqueue(t, Queue("low")); err != nil {
+				b.Fatalf("could not enqueue a task: %v", err)
+			}
+		}
+
+		var wg sync.WaitGroup
+		wg.Add(highCount + defaultCount + lowCount)
+		handler := func(ctx context.Context, t *Task) error {
+			wg.Done()
+			return nil
+		}
+		b.StartTimer() // end setup
+
+		bg.start(HandlerFunc(handler))
+		wg.Wait()
+
+		b.StopTimer() // begin teardown
+		bg.stop()
+		b.StartTimer() // end teardown
+	}
+}
--- a/client.go
+++ b/client.go
@@ -34,8 +34,9 @@ type Option interface{}

 // Internal option representations.
 type (
-	retryOption int
-	queueOption string
+	retryOption   int
+	queueOption   string
+	timeoutOption time.Duration
 )

 // MaxRetry returns an option to specify the max number of times
@@ -56,15 +57,24 @@ func Queue(name string) Option {
 	return queueOption(strings.ToLower(name))
 }

+// Timeout returns an option to specify how long a task may run.
+//
+// Zero duration means no limit.
+func Timeout(d time.Duration) Option {
+	return timeoutOption(d)
+}
+
 type option struct {
-	retry int
-	queue string
+	retry   int
+	queue   string
+	timeout time.Duration
 }

 func composeOptions(opts ...Option) option {
 	res := option{
-		retry: defaultMaxRetry,
-		queue: base.DefaultQueueName,
+		retry:   defaultMaxRetry,
+		queue:   base.DefaultQueueName,
+		timeout: 0,
 	}
 	for _, opt := range opts {
 		switch opt := opt.(type) {
@@ -72,6 +82,8 @@ func composeOptions(opts ...Option) option {
 			res.retry = int(opt)
 		case queueOption:
 			res.queue = string(opt)
+		case timeoutOption:
+			res.timeout = time.Duration(opt)
 		default:
 			// ignore unexpected option
 		}
@@ -84,14 +96,13 @@ const (
 	defaultMaxRetry = 25
 )

-// Schedule registers a task to be processed at the specified time.
+// EnqueueAt schedules task to be enqueued at the specified time.
 //
-// Schedule returns nil if the task is registered successfully,
-// otherwise returns a non-nil error.
+// EnqueueAt returns nil if the task is scheduled successfully, otherwise returns a non-nil error.
 //
-// opts specifies the behavior of task processing. If there are conflicting
-// Option values the last one overrides others.
-func (c *Client) Schedule(task *Task, processAt time.Time, opts ...Option) error {
+// The argument opts specifies the behavior of task processing.
+// If there are conflicting Option values the last one overrides others.
+func (c *Client) EnqueueAt(t time.Time, task *Task, opts ...Option) error {
 	opt := composeOptions(opts...)
 	msg := &base.TaskMessage{
 		ID:      xid.New(),
@@ -99,13 +110,34 @@ func (c *Client) Schedule(task *Task, processAt time.Time, opts ...Option) error
 		Payload: task.Payload.data,
 		Queue:   opt.queue,
 		Retry:   opt.retry,
+		Timeout: opt.timeout.String(),
 	}
-	return c.enqueue(msg, processAt)
+	return c.enqueue(msg, t)
 }

-func (c *Client) enqueue(msg *base.TaskMessage, processAt time.Time) error {
-	if time.Now().After(processAt) {
+// Enqueue enqueues task to be processed immediately.
+//
+// Enqueue returns nil if the task is enqueued successfully, otherwise returns a non-nil error.
+//
+// The argument opts specifies the behavior of task processing.
+// If there are conflicting Option values the last one overrides others.
+func (c *Client) Enqueue(task *Task, opts ...Option) error {
+	return c.EnqueueAt(time.Now(), task, opts...)
+}
+
+// EnqueueIn schedules task to be enqueued after the specified delay.
+//
+// EnqueueIn returns nil if the task is scheduled successfully, otherwise returns a non-nil error.
+//
+// The argument opts specifies the behavior of task processing.
+// If there are conflicting Option values the last one overrides others.
+func (c *Client) EnqueueIn(d time.Duration, task *Task, opts ...Option) error {
+	return c.EnqueueAt(time.Now().Add(d), task, opts...)
+}
+
+func (c *Client) enqueue(msg *base.TaskMessage, t time.Time) error {
+	if time.Now().After(t) {
 		return c.rdb.Enqueue(msg)
 	}
-	return c.rdb.Schedule(msg, processAt)
+	return c.rdb.Schedule(msg, t)
 }
--- a/client_test.go
+++ b/client_test.go
@@ -13,15 +13,20 @@ import (
 	"github.com/hibiken/asynq/internal/base"
 )

-func TestClient(t *testing.T) {
+func TestClientEnqueueAt(t *testing.T) {
 	r := setup(t)
-	client := NewClient(&RedisClientOpt{
-		Addr: "localhost:6379",
-		DB:   14,
+	client := NewClient(RedisClientOpt{
+		Addr: redisAddr,
+		DB:   redisDB,
 	})

 	task := NewTask("send_email", map[string]interface{}{"to": "customer@gmail.com", "from": "merchant@example.com"})

+	var (
+		now          = time.Now()
+		oneHourLater = now.Add(time.Hour)
+	)
+
 	tests := []struct {
 		desc          string
 		task          *Task
@@ -33,7 +38,7 @@ func TestClient(t *testing.T) {
 		{
 			desc:      "Process task immediately",
 			task:      task,
-			processAt: time.Now(),
+			processAt: now,
 			opts:      []Option{},
 			wantEnqueued: map[string][]*base.TaskMessage{
 				"default": []*base.TaskMessage{
@@ -42,6 +47,7 @@ func TestClient(t *testing.T) {
 						Payload: task.Payload.data,
 						Retry:   defaultMaxRetry,
 						Queue:   "default",
+						Timeout: time.Duration(0).String(),
 					},
 				},
 			},
@@ -50,7 +56,7 @@ func TestClient(t *testing.T) {
 		{
 			desc:         "Schedule task to be processed in the future",
 			task:         task,
-			processAt:    time.Now().Add(2 * time.Hour),
+			processAt:    oneHourLater,
 			opts:         []Option{},
 			wantEnqueued: nil, // db is flushed in setup so list does not exist hence nil
 			wantScheduled: []h.ZSetEntry{
@@ -60,113 +66,241 @@ func TestClient(t *testing.T) {
 						Payload: task.Payload.data,
 						Retry:   defaultMaxRetry,
 						Queue:   "default",
+						Timeout: time.Duration(0).String(),
 					},
-					Score: float64(time.Now().Add(2 * time.Hour).Unix()),
+					Score: float64(oneHourLater.Unix()),
 				},
 			},
 		},
-		{
-			desc:      "Process task immediately with a custom retry count",
-			task:      task,
-			processAt: time.Now(),
-			opts: []Option{
-				MaxRetry(3),
-			},
-			wantEnqueued: map[string][]*base.TaskMessage{
-				"default": []*base.TaskMessage{
-					&base.TaskMessage{
-						Type:    task.Type,
-						Payload: task.Payload.data,
-						Retry:   3,
-						Queue:   "default",
-					},
-				},
-			},
-			wantScheduled: nil, // db is flushed in setup so zset does not exist hence nil
-		},
-		{
-			desc:      "Negative retry count",
-			task:      task,
-			processAt: time.Now(),
-			opts: []Option{
-				MaxRetry(-2),
-			},
-			wantEnqueued: map[string][]*base.TaskMessage{
-				"default": []*base.TaskMessage{
-					&base.TaskMessage{
-						Type:    task.Type,
-						Payload: task.Payload.data,
-						Retry:   0, // Retry count should be set to zero
-						Queue:   "default",
-					},
-				},
-			},
-			wantScheduled: nil, // db is flushed in setup so zset does not exist hence nil
-		},
-		{
-			desc:      "Conflicting options",
-			task:      task,
-			processAt: time.Now(),
-			opts: []Option{
-				MaxRetry(2),
-				MaxRetry(10),
-			},
-			wantEnqueued: map[string][]*base.TaskMessage{
-				"default": []*base.TaskMessage{
-					&base.TaskMessage{
-						Type:    task.Type,
-						Payload: task.Payload.data,
-						Retry:   10, // Last option takes precedence
-						Queue:   "default",
-					},
-				},
-			},
-			wantScheduled: nil, // db is flushed in setup so zset does not exist hence nil
-		},
-		{
-			desc:      "With queue option",
-			task:      task,
-			processAt: time.Now(),
-			opts: []Option{
-				Queue("custom"),
-			},
-			wantEnqueued: map[string][]*base.TaskMessage{
-				"custom": []*base.TaskMessage{
-					&base.TaskMessage{
-						Type:    task.Type,
-						Payload: task.Payload.data,
-						Retry:   defaultMaxRetry,
-						Queue:   "custom",
-					},
-				},
-			},
-			wantScheduled: nil, // db is flushed in setup so zset does not exist hence nil
-		},
-		{
-			desc:      "Queue option should be case-insensitive",
-			task:      task,
-			processAt: time.Now(),
-			opts: []Option{
-				Queue("HIGH"),
-			},
-			wantEnqueued: map[string][]*base.TaskMessage{
-				"high": []*base.TaskMessage{
-					&base.TaskMessage{
-						Type:    task.Type,
-						Payload: task.Payload.data,
-						Retry:   defaultMaxRetry,
-						Queue:   "high",
-					},
-				},
-			},
-			wantScheduled: nil, // db is flushed in setup so zset does not exist hence nil
-		},
 	}

 	for _, tc := range tests {
 		h.FlushDB(t, r) // clean up db before each test case.

-		err := client.Schedule(tc.task, tc.processAt, tc.opts...)
+		err := client.EnqueueAt(tc.processAt, tc.task, tc.opts...)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+
+		for qname, want := range tc.wantEnqueued {
+			gotEnqueued := h.GetEnqueuedMessages(t, r, qname)
+			if diff := cmp.Diff(want, gotEnqueued, h.IgnoreIDOpt); diff != "" {
+				t.Errorf("%s;\nmismatch found in %q; (-want,+got)\n%s", tc.desc, base.QueueKey(qname), diff)
+			}
+		}
+
+		gotScheduled := h.GetScheduledEntries(t, r)
+		if diff := cmp.Diff(tc.wantScheduled, gotScheduled, h.IgnoreIDOpt); diff != "" {
+			t.Errorf("%s;\nmismatch found in %q; (-want,+got)\n%s", tc.desc, base.ScheduledQueue, diff)
+		}
+	}
+}
+
+func TestClientEnqueue(t *testing.T) {
+	r := setup(t)
+	client := NewClient(RedisClientOpt{
+		Addr: redisAddr,
+		DB:   redisDB,
+	})
+
+	task := NewTask("send_email", map[string]interface{}{"to": "customer@gmail.com", "from": "merchant@example.com"})
+
+	tests := []struct {
+		desc         string
+		task         *Task
+		opts         []Option
+		wantEnqueued map[string][]*base.TaskMessage
+	}{
+		{
+			desc: "Process task immediately with a custom retry count",
+			task: task,
+			opts: []Option{
+				MaxRetry(3),
+			},
+			wantEnqueued: map[string][]*base.TaskMessage{
+				"default": []*base.TaskMessage{
+					&base.TaskMessage{
+						Type:    task.Type,
+						Payload: task.Payload.data,
+						Retry:   3,
+						Queue:   "default",
+						Timeout: time.Duration(0).String(),
+					},
+				},
+			},
+		},
+		{
+			desc: "Negative retry count",
+			task: task,
+			opts: []Option{
+				MaxRetry(-2),
+			},
+			wantEnqueued: map[string][]*base.TaskMessage{
+				"default": []*base.TaskMessage{
+					&base.TaskMessage{
+						Type:    task.Type,
+						Payload: task.Payload.data,
+						Retry:   0, // Retry count should be set to zero
+						Queue:   "default",
+						Timeout: time.Duration(0).String(),
+					},
+				},
+			},
+		},
+		{
+			desc: "Conflicting options",
+			task: task,
+			opts: []Option{
+				MaxRetry(2),
+				MaxRetry(10),
+			},
+			wantEnqueued: map[string][]*base.TaskMessage{
+				"default": []*base.TaskMessage{
+					&base.TaskMessage{
+						Type:    task.Type,
+						Payload: task.Payload.data,
+						Retry:   10, // Last option takes precedence
+						Queue:   "default",
+						Timeout: time.Duration(0).String(),
+					},
+				},
+			},
+		},
+		{
+			desc: "With queue option",
+			task: task,
+			opts: []Option{
+				Queue("custom"),
+			},
+			wantEnqueued: map[string][]*base.TaskMessage{
+				"custom": []*base.TaskMessage{
+					&base.TaskMessage{
+						Type:    task.Type,
+						Payload: task.Payload.data,
+						Retry:   defaultMaxRetry,
+						Queue:   "custom",
+						Timeout: time.Duration(0).String(),
+					},
+				},
+			},
+		},
+		{
+			desc: "Queue option should be case-insensitive",
+			task: task,
+			opts: []Option{
+				Queue("HIGH"),
+			},
+			wantEnqueued: map[string][]*base.TaskMessage{
+				"high": []*base.TaskMessage{
+					&base.TaskMessage{
+						Type:    task.Type,
+						Payload: task.Payload.data,
+						Retry:   defaultMaxRetry,
+						Queue:   "high",
+						Timeout: time.Duration(0).String(),
+					},
+				},
+			},
+		},
+		{
+			desc: "Timeout option sets the timeout duration",
+			task: task,
+			opts: []Option{
+				Timeout(20 * time.Second),
+			},
+			wantEnqueued: map[string][]*base.TaskMessage{
+				"default": []*base.TaskMessage{
+					&base.TaskMessage{
+						Type:    task.Type,
+						Payload: task.Payload.data,
+						Retry:   defaultMaxRetry,
+						Queue:   "default",
+						Timeout: (20 * time.Second).String(),
+					},
+				},
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		h.FlushDB(t, r) // clean up db before each test case.
+
+		err := client.Enqueue(tc.task, tc.opts...)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+
+		for qname, want := range tc.wantEnqueued {
+			got := h.GetEnqueuedMessages(t, r, qname)
+			if diff := cmp.Diff(want, got, h.IgnoreIDOpt); diff != "" {
+				t.Errorf("%s;\nmismatch found in %q; (-want,+got)\n%s", tc.desc, base.QueueKey(qname), diff)
+			}
+		}
+	}
+}
+
+func TestClientEnqueueIn(t *testing.T) {
+	r := setup(t)
+	client := NewClient(RedisClientOpt{
+		Addr: redisAddr,
+		DB:   redisDB,
+	})
+
+	task := NewTask("send_email", map[string]interface{}{"to": "customer@gmail.com", "from": "merchant@example.com"})
+
+	tests := []struct {
+		desc          string
+		task          *Task
+		delay         time.Duration
+		opts          []Option
+		wantEnqueued  map[string][]*base.TaskMessage
+		wantScheduled []h.ZSetEntry
+	}{
+		{
+			desc:         "schedule a task to be enqueued in one hour",
+			task:         task,
+			delay:        time.Hour,
+			opts:         []Option{},
+			wantEnqueued: nil, // db is flushed in setup so list does not exist hence nil
+			wantScheduled: []h.ZSetEntry{
+				{
+					Msg: &base.TaskMessage{
+						Type:    task.Type,
+						Payload: task.Payload.data,
+						Retry:   defaultMaxRetry,
+						Queue:   "default",
+						Timeout: time.Duration(0).String(),
+					},
+					Score: float64(time.Now().Add(time.Hour).Unix()),
+				},
+			},
+		},
+		{
+			desc:  "Zero delay",
+			task:  task,
+			delay: 0,
+			opts:  []Option{},
+			wantEnqueued: map[string][]*base.TaskMessage{
+				"default": []*base.TaskMessage{
+					&base.TaskMessage{
+						Type:    task.Type,
+						Payload: task.Payload.data,
+						Retry:   defaultMaxRetry,
+						Queue:   "default",
+						Timeout: time.Duration(0).String(),
+					},
+				},
+			},
+			wantScheduled: nil, // db is flushed in setup so zset does not exist hence nil
+		},
+	}
+
+	for _, tc := range tests {
+		h.FlushDB(t, r) // clean up db before each test case.
+
+		err := client.EnqueueIn(tc.delay, tc.task, tc.opts...)
 		if err != nil {
 			t.Error(err)
 			continue
--- a/doc.go
+++ b/doc.go
@@ -9,8 +9,8 @@ Asynq uses Redis as a message broker. To connect to redis server,
 specify the options using one of RedisConnOpt types.

    redis = &asynq.RedisClientOpt{
-        Addr:     "localhost:6379",
-        Password: "secretpassword",
+        Addr:     "127.0.0.1:6379",
+        Password: "xxxxx",
        DB:       3,
    }

@@ -24,8 +24,11 @@ Task is created with two parameters: its type and payload.
        "send_email",
        map[string]interface{}{"user_id": 42})

-    // Schedule the task t to be processed a minute from now.
-    err := client.Schedule(t, time.Now().Add(time.Minute))
+    // Enqueue the task to be processed immediately.
+    err := client.Enqueue(t)
+
+    // Schedule the task to be processed in one minute.
+    err = client.EnqueueIn(time.Minute, t)

 The Background is used to run the background task processing with a given
 handler.
@@ -45,7 +48,7 @@ Example of a type that implements the Handler interface.
        // ...
    }

-    func (h *TaskHandler) ProcessTask(task *asynq.Task) error {
+    func (h *TaskHandler) ProcessTask(ctx context.Context, task *asynq.Task) error {
        switch task.Type {
        case "send_email":
            id, err := task.Payload.GetInt("user_id")
--- a/docs/assets/asynqmon_ps.gif
+++ b/docs/assets/asynqmon_ps.gif
--- a/go.mod
+++ b/go.mod
@@ -3,20 +3,12 @@ module github.com/hibiken/asynq
 go 1.13

 require (
-	github.com/go-redis/redis/v7 v7.0.0-beta.4
+	github.com/go-redis/redis/v7 v7.2.0
 	github.com/google/go-cmp v0.4.0
-	github.com/mitchellh/go-homedir v1.1.0
-	github.com/pelletier/go-toml v1.6.0 // indirect
 	github.com/rs/xid v1.2.1
-	github.com/spf13/afero v1.2.2 // indirect
 	github.com/spf13/cast v1.3.1
-	github.com/spf13/cobra v0.0.5
-	github.com/spf13/jwalterweatherman v1.1.0 // indirect
-	github.com/spf13/pflag v1.0.5 // indirect
-	github.com/spf13/viper v1.6.0
 	go.uber.org/goleak v0.10.0
 	golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e // indirect
-	golang.org/x/text v0.3.2 // indirect
 	golang.org/x/time v0.0.0-20190308202827-9d24e82272b4
 	gopkg.in/yaml.v2 v2.2.7 // indirect
 )
--- a/go.sum
+++ b/go.sum
@@ -1,178 +1,53 @@
-cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
-github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
-github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
-github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
-github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
-github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
-github.com/armon/consul-api v0.0.0-20180202201655-eb2c6b5be1b6/go.mod h1:grANhF5doyWs3UAsr3K4I6qtAmlQcZDesFNEHPZAzj8=
-github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
-github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
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-github.com/subosito/gotenv v1.2.0 h1:Slr1R9HxAlEKefgq5jn9U+DnETlIUa6HfgEzj0g5d7s=
-github.com/subosito/gotenv v1.2.0/go.mod h1:N0PQaV/YGNqwC0u51sEeR/aUtSLEXKX9iv69rRypqCw=
-github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5/go.mod h1:ncp9v5uamzpCO7NfCPTXjqaC+bZgJeR0sMTm6dMHP7U=
-github.com/ugorji/go v1.1.4/go.mod h1:uQMGLiO92mf5W77hV/PUCpI3pbzQx3CRekS0kk+RGrc=
-github.com/ugorji/go/codec v0.0.0-20181204163529-d75b2dcb6bc8/go.mod h1:VFNgLljTbGfSG7qAOspJ7OScBnGdDN/yBr0sguwnwf0=
-github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
-github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
-go.etcd.io/bbolt v1.3.2/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
-go.uber.org/atomic v1.4.0/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/goleak v0.10.0 h1:G3eWbSNIskeRqtsN/1uI5B+eP73y3JUuBsv9AZjehb4=
 go.uber.org/goleak v0.10.0/go.mod h1:VCZuO8V8mFPlL0F5J5GK1rtHV3DrFcQ1R8ryq7FK0aI=
-go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
-go.uber.org/zap v1.10.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
-golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
-golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
-golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
-golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180906233101-161cd47e91fd h1:nTDtHvHSdCn1m6ITfMRqtOd/9+7a3s8RBNOZ3eYZzJA=
 golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
-golang.org/x/net v0.0.0-20181114220301-adae6a3d119a/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
-golang.org/x/net v0.0.0-20181220203305-927f97764cc3/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
-golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190522155817-f3200d17e092 h1:4QSRKanuywn15aTZvI/mIDEgPQpswuFndXpOj3rKEco=
 golang.org/x/net v0.0.0-20190522155817-f3200d17e092/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
-golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
+golang.org/x/net v0.0.0-20190923162816-aa69164e4478/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20200202094626-16171245cfb2 h1:CCH4IOTTfewWjGOlSp+zGcjutRKlBEZQ6wTn8ozI/nI=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e h1:o3PsSEY8E4eXWkXrIP9YJALUkVZqzHJT5DOasTyn8Vs=
 golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20181107165924-66b7b1311ac8/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20181205085412-a5c9d58dba9a h1:1n5lsVfiQW3yfsRGu98756EH1YthsFqr/5mxHduZW2A=
-golang.org/x/sys v0.0.0-20181205085412-a5c9d58dba9a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20191010194322-b09406accb47/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e h1:9vRrk9YW2BTzLP0VCB9ZDjU4cPqkg+IDWL7XgxA1yxQ=
 golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
@@ -181,34 +56,19 @@ golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4 h1:SvFZT6jyqRaOeXpc5h/JSfZenJ2O330aBsf7JfSUXmQ=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
-golang.org/x/tools v0.0.0-20180221164845-07fd8470d635/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20190114222345-bf090417da8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
-golang.org/x/tools v0.0.0-20190328211700-ab21143f2384/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
-google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
-google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=
-google.golang.org/grpc v1.21.0/go.mod h1:oYelfM1adQP15Ek0mdvEgi9Df8B9CZIaU1084ijfRaM=
-gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/fsnotify.v1 v1.4.7 h1:xOHLXZwVvI9hhs+cLKq5+I5onOuwQLhQwiu63xxlHs4=
 gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=
-gopkg.in/ini.v1 v1.51.0 h1:AQvPpx3LzTDM0AjnIRlVFwFFGC+npRopjZxLJj6gdno=
-gopkg.in/ini.v1 v1.51.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
-gopkg.in/resty.v1 v1.12.0/go.mod h1:mDo4pnntr5jdWRML875a/NmxYqAlA73dVijT2AXvQQo=
 gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 h1:uRGJdciOHaEIrze2W8Q3AKkepLTh2hOroT7a+7czfdQ=
 gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7/go.mod h1:dt/ZhP58zS4L8KSrWDmTeBkI65Dw0HsyUHuEVlX15mw=
-gopkg.in/yaml.v2 v2.0.0-20170812160011-eb3733d160e7/go.mod h1:JAlM8MvJe8wmxCU4Bli9HhUf9+ttbYbLASfIpnQbh74=
 gopkg.in/yaml.v2 v2.2.1 h1:mUhvW9EsL+naU5Q3cakzfE91YhliOondGd6ZrsDBHQE=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.7 h1:VUgggvou5XRW9mHwD/yXxIYSMtY0zoKQf/v226p2nyo=
 gopkg.in/yaml.v2 v2.2.7/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
--- a/heartbeat.go
+++ b/heartbeat.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"sync"
 	"time"

 	"github.com/hibiken/asynq/internal/base"
@@ -16,7 +17,7 @@ import (
 type heartbeater struct {
 	rdb *rdb.RDB

-	pinfo *base.ProcessInfo
+	ps *base.ProcessState

 	// channel to communicate back to the long running "heartbeater" goroutine.
 	done chan struct{}
@@ -25,10 +26,10 @@ type heartbeater struct {
 	interval time.Duration
 }

-func newHeartbeater(rdb *rdb.RDB, pinfo *base.ProcessInfo, interval time.Duration) *heartbeater {
+func newHeartbeater(rdb *rdb.RDB, ps *base.ProcessState, interval time.Duration) *heartbeater {
 	return &heartbeater{
 		rdb:      rdb,
-		pinfo:    pinfo,
+		ps:       ps,
 		done:     make(chan struct{}),
 		interval: interval,
 	}
@@ -40,14 +41,17 @@ func (h *heartbeater) terminate() {
 	h.done <- struct{}{}
 }

-func (h *heartbeater) start() {
-	h.pinfo.SetStarted(time.Now())
-	h.pinfo.SetState("running")
+func (h *heartbeater) start(wg *sync.WaitGroup) {
+	h.ps.SetStarted(time.Now())
+	h.ps.SetStatus(base.StatusRunning)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		h.beat()
 		for {
 			select {
 			case <-h.done:
+				h.rdb.ClearProcessState(h.ps)
 				logger.info("Heartbeater done")
 				return
 			case <-time.After(h.interval):
@@ -60,7 +64,7 @@ func (h *heartbeater) start() {
 func (h *heartbeater) beat() {
 	// Note: Set TTL to be long enough so that it won't expire before we write again
 	// and short enough to expire quickly once the process is shut down or killed.
-	err := h.rdb.WriteProcessInfo(h.pinfo, h.interval*2)
+	err := h.rdb.WriteProcessState(h.ps, h.interval*2)
 	if err != nil {
 		logger.error("could not write heartbeat data: %v", err)
 	}
--- a/heartbeat_test.go
+++ b/heartbeat_test.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"sync"
 	"testing"
 	"time"

@@ -23,10 +24,10 @@ func TestHeartbeater(t *testing.T) {
 		interval    time.Duration
 		host        string
 		pid         int
-		queues      map[string]uint
+		queues      map[string]int
 		concurrency int
 	}{
-		{time.Second, "some.address.ec2.aws.com", 45678, map[string]uint{"default": 1}, 10},
+		{time.Second, "localhost", 45678, map[string]int{"default": 1}, 10},
 	}

 	timeCmpOpt := cmpopts.EquateApproxTime(10 * time.Millisecond)
@@ -34,8 +35,11 @@ func TestHeartbeater(t *testing.T) {
 	for _, tc := range tests {
 		h.FlushDB(t, r)

-		pi := base.NewProcessInfo(tc.host, tc.pid, tc.concurrency, tc.queues, false)
-		hb := newHeartbeater(rdbClient, pi, tc.interval)
+		state := base.NewProcessState(tc.host, tc.pid, tc.concurrency, tc.queues, false)
+		hb := newHeartbeater(rdbClient, state, tc.interval)
+
+		var wg sync.WaitGroup
+		hb.start(&wg)

 		want := &base.ProcessInfo{
 			Host:        tc.host,
@@ -43,42 +47,53 @@ func TestHeartbeater(t *testing.T) {
 			Queues:      tc.queues,
 			Concurrency: tc.concurrency,
 			Started:     time.Now(),
-			State:       "running",
+			Status:      "running",
 		}
-		hb.start()

 		// allow for heartbeater to write to redis
 		time.Sleep(tc.interval * 2)

-		got, err := rdbClient.ReadProcessInfo(tc.host, tc.pid)
+		ps, err := rdbClient.ListProcesses()
 		if err != nil {
 			t.Errorf("could not read process status from redis: %v", err)
 			hb.terminate()
 			continue
 		}

-		if diff := cmp.Diff(want, got, timeCmpOpt, ignoreOpt); diff != "" {
-			t.Errorf("redis stored process status %+v, want %+v; (-want, +got)\n%s", got, want, diff)
+		if len(ps) != 1 {
+			t.Errorf("(*RDB).ListProcesses returned %d process info, want 1", len(ps))
 			hb.terminate()
 			continue
 		}

-		// state change
-		pi.SetState("stopped")
+		if diff := cmp.Diff(want, ps[0], timeCmpOpt, ignoreOpt); diff != "" {
+			t.Errorf("redis stored process status %+v, want %+v; (-want, +got)\n%s", ps[0], want, diff)
+			hb.terminate()
+			continue
+		}
+
+		// status change
+		state.SetStatus(base.StatusStopped)

 		// allow for heartbeater to write to redis
 		time.Sleep(tc.interval * 2)

-		want.State = "stopped"
-		got, err = rdbClient.ReadProcessInfo(tc.host, tc.pid)
+		want.Status = "stopped"
+		ps, err = rdbClient.ListProcesses()
 		if err != nil {
 			t.Errorf("could not read process status from redis: %v", err)
 			hb.terminate()
 			continue
 		}

-		if diff := cmp.Diff(want, got, timeCmpOpt, ignoreOpt); diff != "" {
-			t.Errorf("redis stored process status %+v, want %+v; (-want, +got)\n%s", got, want, diff)
+		if len(ps) != 1 {
+			t.Errorf("(*RDB).ListProcesses returned %d process info, want 1", len(ps))
+			hb.terminate()
+			continue
+		}
+
+		if diff := cmp.Diff(want, ps[0], timeCmpOpt, ignoreOpt); diff != "" {
+			t.Errorf("redis stored process status %+v, want %+v; (-want, +got)\n%s", ps[0], want, diff)
 			hb.terminate()
 			continue
 		}
--- a/internal/asynqtest/asynqtest.go
+++ b/internal/asynqtest/asynqtest.go
@@ -53,6 +53,22 @@ var SortProcessInfoOpt = cmp.Transformer("SortProcessInfo", func(in []*base.Proc
 	return out
 })

+// SortWorkerInfoOpt is a cmp.Option to sort base.WorkerInfo for comparing slice of worker info.
+var SortWorkerInfoOpt = cmp.Transformer("SortWorkerInfo", func(in []*base.WorkerInfo) []*base.WorkerInfo {
+	out := append([]*base.WorkerInfo(nil), in...) // Copy input to avoid mutating it
+	sort.Slice(out, func(i, j int) bool {
+		return out[i].ID.String() < out[j].ID.String()
+	})
+	return out
+})
+
+// SortStringSliceOpt is a cmp.Option to sort string slice.
+var SortStringSliceOpt = cmp.Transformer("SortStringSlice", func(in []string) []string {
+	out := append([]string(nil), in...)
+	sort.Strings(out)
+	return out
+})
+
 // IgnoreIDOpt is an cmp.Option to ignore ID field in task messages when comparing.
 var IgnoreIDOpt = cmpopts.IgnoreFields(base.TaskMessage{}, "ID")

--- a/internal/base/base.go
+++ b/internal/base/base.go
@@ -6,6 +6,7 @@
 package base

 import (
+	"context"
 	"fmt"
 	"strings"
 	"sync"
@@ -19,8 +20,10 @@ const DefaultQueueName = "default"

 // Redis keys
 const (
-	psPrefix        = "asynq:ps:"                    // HASH
 	AllProcesses    = "asynq:ps"                     // ZSET
+	psPrefix        = "asynq:ps:"                    // STRING - asynq:ps:<host>:<pid>
+	AllWorkers      = "asynq:workers"                // ZSET
+	workersPrefix   = "asynq:workers:"               // HASH   - asynq:workers:<host:<pid>
 	processedPrefix = "asynq:processed:"             // STRING - asynq:processed:<yyyy-mm-dd>
 	failurePrefix   = "asynq:failure:"               // STRING - asynq:failure:<yyyy-mm-dd>
 	QueuePrefix     = "asynq:queues:"                // LIST   - asynq:queues:<qname>
@@ -30,30 +33,34 @@ const (
 	RetryQueue      = "asynq:retry"                  // ZSET
 	DeadQueue       = "asynq:dead"                   // ZSET
 	InProgressQueue = "asynq:in_progress"            // LIST
+	CancelChannel   = "asynq:cancel"                 // PubSub channel
 )

-// QueueKey returns a redis key string for the given queue name.
+// QueueKey returns a redis key for the given queue name.
 func QueueKey(qname string) string {
 	return QueuePrefix + strings.ToLower(qname)
 }

-// ProcessedKey returns a redis key string for processed count
-// for the given day.
+// ProcessedKey returns a redis key for processed count for the given day.
 func ProcessedKey(t time.Time) string {
 	return processedPrefix + t.UTC().Format("2006-01-02")
 }

-// FailureKey returns a redis key string for failure count
-// for the given day.
+// FailureKey returns a redis key for failure count for the given day.
 func FailureKey(t time.Time) string {
 	return failurePrefix + t.UTC().Format("2006-01-02")
 }

-// ProcessInfoKey returns a redis key string for process info.
+// ProcessInfoKey returns a redis key for process info.
 func ProcessInfoKey(hostname string, pid int) string {
 	return fmt.Sprintf("%s%s:%d", psPrefix, hostname, pid)
 }

+// WorkersKey returns a redis key for the workers given hostname and pid.
+func WorkersKey(hostname string, pid int) string {
+	return fmt.Sprintf("%s%s:%d", workersPrefix, hostname, pid)
+}
+
 // TaskMessage is the internal representation of a task with additional metadata fields.
 // Serialized data of this type gets written to redis.
 type TaskMessage struct {
@@ -77,49 +84,220 @@ type TaskMessage struct {

 	// ErrorMsg holds the error message from the last failure.
 	ErrorMsg string
+
+	// Timeout specifies how long a task may run.
+	// The string value should be compatible with time.Duration.ParseDuration.
+	//
+	// Zero means no limit.
+	Timeout string
 }

-// ProcessInfo holds information about running background worker process.
+// ProcessState holds process level information.
+//
+// ProcessStates are safe for concurrent use by multiple goroutines.
+type ProcessState struct {
+	mu             sync.Mutex // guards all data fields
+	concurrency    int
+	queues         map[string]int
+	strictPriority bool
+	pid            int
+	host           string
+	status         PStatus
+	started        time.Time
+	workers        map[string]*workerStats
+}
+
+// PStatus represents status of a process.
+type PStatus int
+
+const (
+	// StatusIdle indicates process is in idle state.
+	StatusIdle PStatus = iota
+
+	// StatusRunning indicates process is up and processing tasks.
+	StatusRunning
+
+	// StatusStopped indicates process is up but not processing new tasks.
+	StatusStopped
+)
+
+var statuses = []string{
+	"idle",
+	"running",
+	"stopped",
+}
+
+func (s PStatus) String() string {
+	if StatusIdle <= s && s <= StatusStopped {
+		return statuses[s]
+	}
+	return "unknown status"
+}
+
+type workerStats struct {
+	msg     *TaskMessage
+	started time.Time
+}
+
+// NewProcessState returns a new instance of ProcessState.
+func NewProcessState(host string, pid, concurrency int, queues map[string]int, strict bool) *ProcessState {
+	return &ProcessState{
+		host:           host,
+		pid:            pid,
+		concurrency:    concurrency,
+		queues:         cloneQueueConfig(queues),
+		strictPriority: strict,
+		status:         StatusIdle,
+		workers:        make(map[string]*workerStats),
+	}
+}
+
+// SetStatus updates the state of process.
+func (ps *ProcessState) SetStatus(status PStatus) {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+	ps.status = status
+}
+
+// SetStarted records when the process started processing.
+func (ps *ProcessState) SetStarted(t time.Time) {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+	ps.started = t
+}
+
+// AddWorkerStats records when a worker started and which task it's processing.
+func (ps *ProcessState) AddWorkerStats(msg *TaskMessage, started time.Time) {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+	ps.workers[msg.ID.String()] = &workerStats{msg, started}
+}
+
+// DeleteWorkerStats removes a worker's entry from the process state.
+func (ps *ProcessState) DeleteWorkerStats(msg *TaskMessage) {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+	delete(ps.workers, msg.ID.String())
+}
+
+// Get returns current state of process as a ProcessInfo.
+func (ps *ProcessState) Get() *ProcessInfo {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+	return &ProcessInfo{
+		Host:              ps.host,
+		PID:               ps.pid,
+		Concurrency:       ps.concurrency,
+		Queues:            cloneQueueConfig(ps.queues),
+		StrictPriority:    ps.strictPriority,
+		Status:            ps.status.String(),
+		Started:           ps.started,
+		ActiveWorkerCount: len(ps.workers),
+	}
+}
+
+// GetWorkers returns a list of currently running workers' info.
+func (ps *ProcessState) GetWorkers() []*WorkerInfo {
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+	var res []*WorkerInfo
+	for _, w := range ps.workers {
+		res = append(res, &WorkerInfo{
+			Host:    ps.host,
+			PID:     ps.pid,
+			ID:      w.msg.ID,
+			Type:    w.msg.Type,
+			Queue:   w.msg.Queue,
+			Payload: clonePayload(w.msg.Payload),
+			Started: w.started,
+		})
+	}
+	return res
+}
+
+func cloneQueueConfig(qcfg map[string]int) map[string]int {
+	res := make(map[string]int)
+	for qname, n := range qcfg {
+		res[qname] = n
+	}
+	return res
+}
+
+func clonePayload(payload map[string]interface{}) map[string]interface{} {
+	res := make(map[string]interface{})
+	for k, v := range payload {
+		res[k] = v
+	}
+	return res
+}
+
+// ProcessInfo holds information about a running background worker process.
 type ProcessInfo struct {
-	mu                sync.Mutex
-	Concurrency       int
-	Queues            map[string]uint
-	StrictPriority    bool
-	PID               int
 	Host              string
-	State             string
+	PID               int
+	Concurrency       int
+	Queues            map[string]int
+	StrictPriority    bool
+	Status            string
 	Started           time.Time
 	ActiveWorkerCount int
 }

-// NewProcessInfo returns a new instance of ProcessInfo.
-func NewProcessInfo(host string, pid, concurrency int, queues map[string]uint, strict bool) *ProcessInfo {
-	return &ProcessInfo{
-		Host:           host,
-		PID:            pid,
-		Concurrency:    concurrency,
-		Queues:         queues,
-		StrictPriority: strict,
+// WorkerInfo holds information about a running worker.
+type WorkerInfo struct {
+	Host    string
+	PID     int
+	ID      xid.ID
+	Type    string
+	Queue   string
+	Payload map[string]interface{}
+	Started time.Time
+}
+
+// Cancelations is a collection that holds cancel functions for all in-progress tasks.
+//
+// Cancelations are safe for concurrent use by multipel goroutines.
+type Cancelations struct {
+	mu          sync.Mutex
+	cancelFuncs map[string]context.CancelFunc
+}
+
+// NewCancelations returns a Cancelations instance.
+func NewCancelations() *Cancelations {
+	return &Cancelations{
+		cancelFuncs: make(map[string]context.CancelFunc),
 	}
 }

-// SetState set the state field of the process info.
-func (p *ProcessInfo) SetState(state string) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
-	p.State = state
+// Add adds a new cancel func to the collection.
+func (c *Cancelations) Add(id string, fn context.CancelFunc) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.cancelFuncs[id] = fn
 }

-// SetStarted set the started field of the process info.
-func (p *ProcessInfo) SetStarted(t time.Time) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
-	p.Started = t
+// Delete deletes a cancel func from the collection given an id.
+func (c *Cancelations) Delete(id string) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	delete(c.cancelFuncs, id)
 }

-// IncrActiveWorkerCount increments active worker count by delta.
-func (p *ProcessInfo) IncrActiveWorkerCount(delta int) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
-	p.ActiveWorkerCount += delta
+// Get returns a cancel func given an id.
+func (c *Cancelations) Get(id string) (fn context.CancelFunc, ok bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	fn, ok = c.cancelFuncs[id]
+	return fn, ok
+}
+
+// GetAll returns all cancel funcs.
+func (c *Cancelations) GetAll() []context.CancelFunc {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	var res []context.CancelFunc
+	for _, fn := range c.cancelFuncs {
+		res = append(res, fn)
+	}
+	return res
 }
--- a/internal/base/base_test.go
+++ b/internal/base/base_test.go
@@ -5,9 +5,14 @@
 package base

 import (
+	"context"
+	"math/rand"
 	"sync"
 	"testing"
 	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/rs/xid"
 )

 func TestQueueKey(t *testing.T) {
@@ -75,34 +80,137 @@ func TestProcessInfoKey(t *testing.T) {
 	for _, tc := range tests {
 		got := ProcessInfoKey(tc.hostname, tc.pid)
 		if got != tc.want {
-			t.Errorf("ProcessInfoKey(%s, %d) = %s, want %s", tc.hostname, tc.pid, got, tc.want)
+			t.Errorf("ProcessInfoKey(%q, %d) = %q, want %q", tc.hostname, tc.pid, got, tc.want)
 		}
 	}
 }

-// Note: Run this test with -race flag to check for data race.
-func TestProcessInfoSetter(t *testing.T) {
-	pi := NewProcessInfo("localhost", 1234, 8, map[string]uint{"default": 1}, false)
+func TestWorkersKey(t *testing.T) {
+	tests := []struct {
+		hostname string
+		pid      int
+		want     string
+	}{
+		{"localhost", 9876, "asynq:workers:localhost:9876"},
+		{"127.0.0.1", 1234, "asynq:workers:127.0.0.1:1234"},
+	}

+	for _, tc := range tests {
+		got := WorkersKey(tc.hostname, tc.pid)
+		if got != tc.want {
+			t.Errorf("WorkersKey(%q, %d) = %q, want = %q", tc.hostname, tc.pid, got, tc.want)
+		}
+	}
+}
+
+// Test for process state being accessed by multiple goroutines.
+// Run with -race flag to check for data race.
+func TestProcessStateConcurrentAccess(t *testing.T) {
+	ps := NewProcessState("127.0.0.1", 1234, 10, map[string]int{"default": 1}, false)
 	var wg sync.WaitGroup
+	started := time.Now()
+	msgs := []*TaskMessage{
+		&TaskMessage{ID: xid.New(), Type: "type1", Payload: map[string]interface{}{"user_id": 42}},
+		&TaskMessage{ID: xid.New(), Type: "type2"},
+		&TaskMessage{ID: xid.New(), Type: "type3"},
+	}

-	wg.Add(3)
-
+	// Simulate hearbeater calling SetStatus and SetStarted.
+	wg.Add(1)
 	go func() {
-		pi.SetState("runnning")
-		wg.Done()
+		defer wg.Done()
+		ps.SetStarted(started)
+		ps.SetStatus(StatusRunning)
 	}()

-	go func() {
-		pi.SetStarted(time.Now())
-		pi.IncrActiveWorkerCount(1)
-		wg.Done()
-	}()
+	// Simulate processor starting worker goroutines.
+	for _, msg := range msgs {
+		wg.Add(1)
+		ps.AddWorkerStats(msg, time.Now())
+		go func(msg *TaskMessage) {
+			defer wg.Done()
+			time.Sleep(time.Duration(rand.Intn(500)) * time.Millisecond)
+			ps.DeleteWorkerStats(msg)
+		}(msg)
+	}

+	// Simulate hearbeater calling Get and GetWorkers
+	wg.Add(1)
 	go func() {
-		pi.SetState("stopped")
 		wg.Done()
+		for i := 0; i < 5; i++ {
+			ps.Get()
+			ps.GetWorkers()
+			time.Sleep(time.Duration(rand.Intn(100)) * time.Millisecond)
+		}
 	}()

 	wg.Wait()
+
+	want := &ProcessInfo{
+		Host:              "127.0.0.1",
+		PID:               1234,
+		Concurrency:       10,
+		Queues:            map[string]int{"default": 1},
+		StrictPriority:    false,
+		Status:            "running",
+		Started:           started,
+		ActiveWorkerCount: 0,
+	}
+
+	got := ps.Get()
+	if diff := cmp.Diff(want, got); diff != "" {
+		t.Errorf("(*ProcessState).Get() = %+v, want %+v; (-want,+got)\n%s",
+			got, want, diff)
+	}
+}
+
+// Test for cancelations being accessed by multiple goroutines.
+// Run with -race flag to check for data race.
+func TestCancelationsConcurrentAccess(t *testing.T) {
+	c := NewCancelations()
+
+	_, cancel1 := context.WithCancel(context.Background())
+	_, cancel2 := context.WithCancel(context.Background())
+	_, cancel3 := context.WithCancel(context.Background())
+	var key1, key2, key3 = "key1", "key2", "key3"
+
+	var wg sync.WaitGroup
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		c.Add(key1, cancel1)
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		c.Add(key2, cancel2)
+		time.Sleep(200 * time.Millisecond)
+		c.Delete(key2)
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		c.Add(key3, cancel3)
+	}()
+
+	wg.Wait()
+
+	_, ok := c.Get(key1)
+	if !ok {
+		t.Errorf("(*Cancelations).Get(%q) = _, false, want <function>, true", key1)
+	}
+
+	_, ok = c.Get(key2)
+	if ok {
+		t.Errorf("(*Cancelations).Get(%q) = _, true, want <nil>, false", key2)
+	}
+
+	funcs := c.GetAll()
+	if len(funcs) != 2 {
+		t.Errorf("(*Cancelations).GetAll() returns %d functions, want 2", len(funcs))
+	}
 }
--- a/internal/rdb/inspect.go
+++ b/internal/rdb/inspect.go
@@ -86,49 +86,48 @@ type DeadTask struct {
 	Queue        string
 }

+// KEYS[1] -> asynq:queues
+// KEYS[2] -> asynq:in_progress
+// KEYS[3] -> asynq:scheduled
+// KEYS[4] -> asynq:retry
+// KEYS[5] -> asynq:dead
+// KEYS[6] -> asynq:processed:<yyyy-mm-dd>
+// KEYS[7] -> asynq:failure:<yyyy-mm-dd>
+var currentStatsCmd = redis.NewScript(`
+local res = {}
+local queues = redis.call("SMEMBERS", KEYS[1])
+for _, qkey in ipairs(queues) do
+	table.insert(res, qkey)
+	table.insert(res, redis.call("LLEN", qkey))
+end
+table.insert(res, KEYS[2])
+table.insert(res, redis.call("LLEN", KEYS[2]))
+table.insert(res, KEYS[3])
+table.insert(res, redis.call("ZCARD", KEYS[3]))
+table.insert(res, KEYS[4])
+table.insert(res, redis.call("ZCARD", KEYS[4]))
+table.insert(res, KEYS[5])
+table.insert(res, redis.call("ZCARD", KEYS[5]))
+local pcount = 0
+local p = redis.call("GET", KEYS[6])
+if p then
+	pcount = tonumber(p) 
+end
+table.insert(res, "processed")
+table.insert(res, pcount)
+local fcount = 0
+local f = redis.call("GET", KEYS[7])
+if f then
+	fcount = tonumber(f)
+end
+table.insert(res, "failed")
+table.insert(res, fcount)
+return res`)
+
 // CurrentStats returns a current state of the queues.
 func (r *RDB) CurrentStats() (*Stats, error) {
-	// KEYS[1] -> asynq:queues
-	// KEYS[2] -> asynq:in_progress
-	// KEYS[3] -> asynq:scheduled
-	// KEYS[4] -> asynq:retry
-	// KEYS[5] -> asynq:dead
-	// KEYS[6] -> asynq:processed:<yyyy-mm-dd>
-	// KEYS[7] -> asynq:failure:<yyyy-mm-dd>
-	script := redis.NewScript(`
-	local res = {}
-	local queues = redis.call("SMEMBERS", KEYS[1])
-	for _, qkey in ipairs(queues) do
-	  table.insert(res, qkey)
-	  table.insert(res, redis.call("LLEN", qkey))
-	end
-	table.insert(res, KEYS[2])
-	table.insert(res, redis.call("LLEN", KEYS[2]))
-	table.insert(res, KEYS[3])
-	table.insert(res, redis.call("ZCARD", KEYS[3]))
-	table.insert(res, KEYS[4])
-	table.insert(res, redis.call("ZCARD", KEYS[4]))
-	table.insert(res, KEYS[5])
-	table.insert(res, redis.call("ZCARD", KEYS[5]))
-	local pcount = 0
-	local p = redis.call("GET", KEYS[6])
-	if p then
-		pcount = tonumber(p) 
-	end
-	table.insert(res, "processed")
-	table.insert(res, pcount)
-	local fcount = 0
-	local f = redis.call("GET", KEYS[7])
-	if f then
-		fcount = tonumber(f)
-	end
-	table.insert(res, "failed")
-	table.insert(res, fcount)
-	return res
-	`)
-
 	now := time.Now()
-	res, err := script.Run(r.client, []string{
+	res, err := currentStatsCmd.Run(r.client, []string{
 		base.AllQueues,
 		base.InProgressQueue,
 		base.ScheduledQueue,
@@ -173,6 +172,17 @@ func (r *RDB) CurrentStats() (*Stats, error) {
 	return stats, nil
 }

+var historicalStatsCmd = redis.NewScript(`
+local res = {}
+for _, key in ipairs(KEYS) do
+	local n = redis.call("GET", key)
+	if not n then
+	n = 0
+	end
+	table.insert(res, tonumber(n))
+end
+return res`)
+
 // HistoricalStats returns a list of stats from the last n days.
 func (r *RDB) HistoricalStats(n int) ([]*DailyStats, error) {
 	if n < 1 {
@@ -188,18 +198,7 @@ func (r *RDB) HistoricalStats(n int) ([]*DailyStats, error) {
 		keys = append(keys, base.ProcessedKey(ts))
 		keys = append(keys, base.FailureKey(ts))
 	}
-	script := redis.NewScript(`
-	local res = {}
-	for _, key in ipairs(KEYS) do
-	  local n = redis.call("GET", key)
-	  if not n then
-		n = 0
-	  end
-	  table.insert(res, tonumber(n))
-	end
-	return res
-	`)
-	res, err := script.Run(r.client, keys, len(keys)).Result()
+	res, err := historicalStatsCmd.Run(r.client, keys, len(keys)).Result()
 	if err != nil {
 		return nil, err
 	}
@@ -246,10 +245,10 @@ func reverse(x []string) {
 // for the list operation.
 type Pagination struct {
 	// Number of items in the page.
-	Size uint
+	Size int

 	// Page number starting from zero.
-	Page uint
+	Page int
 }

 func (p Pagination) start() int64 {
@@ -475,21 +474,21 @@ func (r *RDB) EnqueueAllDeadTasks() (int64, error) {
 	return r.removeAndEnqueueAll(base.DeadQueue)
 }

-func (r *RDB) removeAndEnqueue(zset, id string, score float64) (int64, error) {
-	script := redis.NewScript(`
-	local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], ARGV[1], ARGV[1])
-	for _, msg in ipairs(msgs) do
-		local decoded = cjson.decode(msg)
-		if decoded["ID"] == ARGV[2] then
-			redis.call("ZREM", KEYS[1], msg)
-			local qkey = ARGV[3] .. decoded["Queue"]
-			redis.call("LPUSH", qkey, msg)
-			return 1
-		end
+var removeAndEnqueueCmd = redis.NewScript(`
+local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], ARGV[1], ARGV[1])
+for _, msg in ipairs(msgs) do
+	local decoded = cjson.decode(msg)
+	if decoded["ID"] == ARGV[2] then
+		local qkey = ARGV[3] .. decoded["Queue"]
+		redis.call("LPUSH", qkey, msg)
+		redis.call("ZREM", KEYS[1], msg)
+		return 1
 	end
-	return 0
-	`)
-	res, err := script.Run(r.client, []string{zset}, score, id, base.QueuePrefix).Result()
+end
+return 0`)
+
+func (r *RDB) removeAndEnqueue(zset, id string, score float64) (int64, error) {
+	res, err := removeAndEnqueueCmd.Run(r.client, []string{zset}, score, id, base.QueuePrefix).Result()
 	if err != nil {
 		return 0, err
 	}
@@ -500,18 +499,18 @@ func (r *RDB) removeAndEnqueue(zset, id string, score float64) (int64, error) {
 	return n, nil
 }

+var removeAndEnqueueAllCmd = redis.NewScript(`
+local msgs = redis.call("ZRANGE", KEYS[1], 0, -1)
+for _, msg in ipairs(msgs) do
+	local decoded = cjson.decode(msg)
+	local qkey = ARGV[1] .. decoded["Queue"]
+	redis.call("LPUSH", qkey, msg)
+	redis.call("ZREM", KEYS[1], msg)
+end
+return table.getn(msgs)`)
+
 func (r *RDB) removeAndEnqueueAll(zset string) (int64, error) {
-	script := redis.NewScript(`
-	local msgs = redis.call("ZRANGE", KEYS[1], 0, -1)
-	for _, msg in ipairs(msgs) do
-		redis.call("ZREM", KEYS[1], msg)
-		local decoded = cjson.decode(msg)
-		local qkey = ARGV[1] .. decoded["Queue"]
-		redis.call("LPUSH", qkey, msg)
-	end
-	return table.getn(msgs)
-	`)
-	res, err := script.Run(r.client, []string{zset}, base.QueuePrefix).Result()
+	res, err := removeAndEnqueueAllCmd.Run(r.client, []string{zset}, base.QueuePrefix).Result()
 	if err != nil {
 		return 0, err
 	}
@@ -562,31 +561,31 @@ func (r *RDB) KillAllScheduledTasks() (int64, error) {
 	return r.removeAndKillAll(base.ScheduledQueue)
 }

-func (r *RDB) removeAndKill(zset, id string, score float64) (int64, error) {
-	// KEYS[1] -> ZSET to move task from (e.g., retry queue)
-	// KEYS[2] -> asynq:dead
-	// ARGV[1] -> score of the task to kill
-	// ARGV[2] -> id of the task to kill
-	// ARGV[3] -> current timestamp
-	// ARGV[4] -> cutoff timestamp (e.g., 90 days ago)
-	// ARGV[5] -> max number of tasks in dead queue (e.g., 100)
-	script := redis.NewScript(`
-	local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], ARGV[1], ARGV[1])
-	for _, msg in ipairs(msgs) do
-		local decoded = cjson.decode(msg)
-		if decoded["ID"] == ARGV[2] then
-			redis.call("ZREM", KEYS[1], msg)
-			redis.call("ZADD", KEYS[2], ARGV[3], msg)
-			redis.call("ZREMRANGEBYSCORE", KEYS[2], "-inf", ARGV[4])
-			redis.call("ZREMRANGEBYRANK", KEYS[2], 0, -ARGV[5])
-			return 1
-		end
+// KEYS[1] -> ZSET to move task from (e.g., retry queue)
+// KEYS[2] -> asynq:dead
+// ARGV[1] -> score of the task to kill
+// ARGV[2] -> id of the task to kill
+// ARGV[3] -> current timestamp
+// ARGV[4] -> cutoff timestamp (e.g., 90 days ago)
+// ARGV[5] -> max number of tasks in dead queue (e.g., 100)
+var removeAndKillCmd = redis.NewScript(`
+local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], ARGV[1], ARGV[1])
+for _, msg in ipairs(msgs) do
+	local decoded = cjson.decode(msg)
+	if decoded["ID"] == ARGV[2] then
+		redis.call("ZREM", KEYS[1], msg)
+		redis.call("ZADD", KEYS[2], ARGV[3], msg)
+		redis.call("ZREMRANGEBYSCORE", KEYS[2], "-inf", ARGV[4])
+		redis.call("ZREMRANGEBYRANK", KEYS[2], 0, -ARGV[5])
+		return 1
 	end
-	return 0
-	`)
+end
+return 0`)
+
+func (r *RDB) removeAndKill(zset, id string, score float64) (int64, error) {
 	now := time.Now()
 	limit := now.AddDate(0, 0, -deadExpirationInDays).Unix() // 90 days ago
-	res, err := script.Run(r.client,
+	res, err := removeAndKillCmd.Run(r.client,
 		[]string{zset, base.DeadQueue},
 		score, id, now.Unix(), limit, maxDeadTasks).Result()
 	if err != nil {
@@ -599,25 +598,25 @@ func (r *RDB) removeAndKill(zset, id string, score float64) (int64, error) {
 	return n, nil
 }

+// KEYS[1] -> ZSET to move task from (e.g., retry queue)
+// KEYS[2] -> asynq:dead
+// ARGV[1] -> current timestamp
+// ARGV[2] -> cutoff timestamp (e.g., 90 days ago)
+// ARGV[3] -> max number of tasks in dead queue (e.g., 100)
+var removeAndKillAllCmd = redis.NewScript(`
+local msgs = redis.call("ZRANGE", KEYS[1], 0, -1)
+for _, msg in ipairs(msgs) do
+	redis.call("ZADD", KEYS[2], ARGV[1], msg)
+	redis.call("ZREM", KEYS[1], msg)
+	redis.call("ZREMRANGEBYSCORE", KEYS[2], "-inf", ARGV[2])
+	redis.call("ZREMRANGEBYRANK", KEYS[2], 0, -ARGV[3])
+end
+return table.getn(msgs)`)
+
 func (r *RDB) removeAndKillAll(zset string) (int64, error) {
-	// KEYS[1] -> ZSET to move task from (e.g., retry queue)
-	// KEYS[2] -> asynq:dead
-	// ARGV[1] -> current timestamp
-	// ARGV[2] -> cutoff timestamp (e.g., 90 days ago)
-	// ARGV[3] -> max number of tasks in dead queue (e.g., 100)
-	script := redis.NewScript(`
-	local msgs = redis.call("ZRANGE", KEYS[1], 0, -1)
-	for _, msg in ipairs(msgs) do
-		redis.call("ZREM", KEYS[1], msg)
-		redis.call("ZADD", KEYS[2], ARGV[1], msg)
-		redis.call("ZREMRANGEBYSCORE", KEYS[2], "-inf", ARGV[2])
-		redis.call("ZREMRANGEBYRANK", KEYS[2], 0, -ARGV[3])
-	end
-	return table.getn(msgs)
-	`)
 	now := time.Now()
 	limit := now.AddDate(0, 0, -deadExpirationInDays).Unix() // 90 days ago
-	res, err := script.Run(r.client, []string{zset, base.DeadQueue},
+	res, err := removeAndKillAllCmd.Run(r.client, []string{zset, base.DeadQueue},
 		now.Unix(), limit, maxDeadTasks).Result()
 	if err != nil {
 		return 0, err
@@ -650,19 +649,19 @@ func (r *RDB) DeleteScheduledTask(id xid.ID, score int64) error {
 	return r.deleteTask(base.ScheduledQueue, id.String(), float64(score))
 }

-func (r *RDB) deleteTask(zset, id string, score float64) error {
-	script := redis.NewScript(`
-	local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], ARGV[1], ARGV[1])
-	for _, msg in ipairs(msgs) do
-		local decoded = cjson.decode(msg)
-		if decoded["ID"] == ARGV[2] then
-			redis.call("ZREM", KEYS[1], msg)
-			return 1
-		end
+var deleteTaskCmd = redis.NewScript(`
+local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], ARGV[1], ARGV[1])
+for _, msg in ipairs(msgs) do
+	local decoded = cjson.decode(msg)
+	if decoded["ID"] == ARGV[2] then
+		redis.call("ZREM", KEYS[1], msg)
+		return 1
 	end
-	return 0
-	`)
-	res, err := script.Run(r.client, []string{zset}, score, id).Result()
+end
+return 0`)
+
+func (r *RDB) deleteTask(zset, id string, score float64) error {
+	res, err := deleteTaskCmd.Run(r.client, []string{zset}, score, id).Result()
 	if err != nil {
 		return err
 	}
@@ -709,6 +708,27 @@ func (e *ErrQueueNotEmpty) Error() string {
 	return fmt.Sprintf("queue %q is not empty", e.qname)
 }

+// Skip checking whether queue is empty before removing.
+var removeQueueForceCmd = redis.NewScript(`
+local n = redis.call("SREM", KEYS[1], KEYS[2])
+if n == 0 then
+	return redis.error_reply("LIST NOT FOUND")
+end
+redis.call("DEL", KEYS[2])
+return redis.status_reply("OK")`)
+
+// Checks whether queue is empty before removing.
+var removeQueueCmd = redis.NewScript(`
+local l = redis.call("LLEN", KEYS[2]) if l > 0 then
+	return redis.error_reply("LIST NOT EMPTY")
+end
+local n = redis.call("SREM", KEYS[1], KEYS[2])
+if n == 0 then
+	return redis.error_reply("LIST NOT FOUND")
+end
+redis.call("DEL", KEYS[2])
+return redis.status_reply("OK")`)
+
 // RemoveQueue removes the specified queue.
 //
 // If force is set to true, it will remove the queue regardless
@@ -718,27 +738,9 @@ func (e *ErrQueueNotEmpty) Error() string {
 func (r *RDB) RemoveQueue(qname string, force bool) error {
 	var script *redis.Script
 	if force {
-		script = redis.NewScript(`
-		local n = redis.call("SREM", KEYS[1], KEYS[2])
-		if n == 0 then
-			return redis.error_reply("LIST NOT FOUND")
-		end
-		redis.call("DEL", KEYS[2])
-		return redis.status_reply("OK")
-		`)
+		script = removeQueueForceCmd
 	} else {
-		script = redis.NewScript(`
-		local l = redis.call("LLEN", KEYS[2])
-		if l > 0 then
-			return redis.error_reply("LIST NOT EMPTY")
-		end
-		local n = redis.call("SREM", KEYS[1], KEYS[2])
-		if n == 0 then
-			return redis.error_reply("LIST NOT FOUND")
-		end
-		redis.call("DEL", KEYS[2])
-		return redis.status_reply("OK")
-		`)
+		script = removeQueueCmd
 	}
 	err := script.Run(r.client,
 		[]string{base.AllQueues, base.QueueKey(qname)},
@@ -756,23 +758,23 @@ func (r *RDB) RemoveQueue(qname string, force bool) error {
 	return nil
 }

+// Note: Script also removes stale keys.
+var listProcessesCmd = redis.NewScript(`
+local res = {}
+local now = tonumber(ARGV[1])
+local keys = redis.call("ZRANGEBYSCORE", KEYS[1], now, "+inf")
+for _, key in ipairs(keys) do
+	local ps = redis.call("GET", key)
+	if ps then
+		table.insert(res, ps)
+	end  
+end
+redis.call("ZREMRANGEBYSCORE", KEYS[1], "-inf", now-1)
+return res`)
+
 // ListProcesses returns the list of process statuses.
 func (r *RDB) ListProcesses() ([]*base.ProcessInfo, error) {
-	// Note: Script also removes stale keys.
-	script := redis.NewScript(`
-	local res = {}
-	local now = tonumber(ARGV[1])
-	local keys = redis.call("ZRANGEBYSCORE", KEYS[1], now, "+inf")
-	for _, key in ipairs(keys) do
-		local ps = redis.call("GET", key)
-		if ps then
-			table.insert(res, ps)
-		end  
-	end
-	redis.call("ZREMRANGEBYSCORE", KEYS[1], "-inf", now-1)
-	return res
-	`)
-	res, err := script.Run(r.client,
+	res, err := listProcessesCmd.Run(r.client,
 		[]string{base.AllProcesses}, time.Now().UTC().Unix()).Result()
 	if err != nil {
 		return nil, err
@@ -792,3 +794,39 @@ func (r *RDB) ListProcesses() ([]*base.ProcessInfo, error) {
 	}
 	return processes, nil
 }
+
+// Note: Script also removes stale keys.
+var listWorkersCmd = redis.NewScript(`
+local res = {}
+local now = tonumber(ARGV[1])
+local keys = redis.call("ZRANGEBYSCORE", KEYS[1], now, "+inf")
+for _, key in ipairs(keys) do
+	local workers = redis.call("HVALS", key)
+	for _, w in ipairs(workers) do
+		table.insert(res, w)
+	end  
+end
+redis.call("ZREMRANGEBYSCORE", KEYS[1], "-inf", now-1)
+return res`)
+
+// ListWorkers returns the list of worker stats.
+func (r *RDB) ListWorkers() ([]*base.WorkerInfo, error) {
+	res, err := listWorkersCmd.Run(r.client, []string{base.AllWorkers}, time.Now().UTC().Unix()).Result()
+	if err != nil {
+		return nil, err
+	}
+	data, err := cast.ToStringSliceE(res)
+	if err != nil {
+		return nil, err
+	}
+	var workers []*base.WorkerInfo
+	for _, s := range data {
+		var w base.WorkerInfo
+		err := json.Unmarshal([]byte(s), &w)
+		if err != nil {
+			continue // skip bad data
+		}
+		workers = append(workers, &w)
+	}
+	return workers, nil
+}
--- a/internal/rdb/inspect_test.go
+++ b/internal/rdb/inspect_test.go
@@ -317,8 +317,8 @@ func TestListEnqueuedPagination(t *testing.T) {
 	tests := []struct {
 		desc      string
 		qname     string
-		page      uint
-		size      uint
+		page      int
+		size      int
 		wantSize  int
 		wantFirst string
 		wantLast  string
@@ -418,8 +418,8 @@ func TestListInProgressPagination(t *testing.T) {

 	tests := []struct {
 		desc      string
-		page      uint
-		size      uint
+		page      int
+		size      int
 		wantSize  int
 		wantFirst string
 		wantLast  string
@@ -524,8 +524,8 @@ func TestListScheduledPagination(t *testing.T) {

 	tests := []struct {
 		desc      string
-		page      uint
-		size      uint
+		page      int
+		size      int
 		wantSize  int
 		wantFirst string
 		wantLast  string
@@ -667,8 +667,8 @@ func TestListRetryPagination(t *testing.T) {

 	tests := []struct {
 		desc      string
-		page      uint
-		size      uint
+		page      int
+		size      int
 		wantSize  int
 		wantFirst string
 		wantLast  string
@@ -800,8 +800,8 @@ func TestListDeadPagination(t *testing.T) {

 	tests := []struct {
 		desc      string
-		page      uint
-		size      uint
+		page      int
+		size      int
 		wantSize  int
 		wantFirst string
 		wantLast  string
@@ -2054,32 +2054,51 @@ func TestRemoveQueueError(t *testing.T) {
 func TestListProcesses(t *testing.T) {
 	r := setup(t)

-	ps1 := &base.ProcessInfo{
+	started1 := time.Now().Add(-time.Hour)
+	ps1 := base.NewProcessState("do.droplet1", 1234, 10, map[string]int{"default": 1}, false)
+	ps1.SetStarted(started1)
+	ps1.SetStatus(base.StatusRunning)
+	info1 := &base.ProcessInfo{
 		Concurrency:       10,
-		Queues:            map[string]uint{"default": 1},
+		Queues:            map[string]int{"default": 1},
 		Host:              "do.droplet1",
 		PID:               1234,
-		State:             "running",
-		Started:           time.Now().Add(-time.Hour),
-		ActiveWorkerCount: 5,
+		Status:            "running",
+		Started:           started1,
+		ActiveWorkerCount: 0,
 	}

-	ps2 := &base.ProcessInfo{
+	started2 := time.Now().Add(-2 * time.Hour)
+	ps2 := base.NewProcessState("do.droplet2", 9876, 20, map[string]int{"email": 1}, false)
+	ps2.SetStarted(started2)
+	ps2.SetStatus(base.StatusStopped)
+	ps2.AddWorkerStats(h.NewTaskMessage("send_email", nil), time.Now())
+	info2 := &base.ProcessInfo{
 		Concurrency:       20,
-		Queues:            map[string]uint{"email": 1},
+		Queues:            map[string]int{"email": 1},
 		Host:              "do.droplet2",
 		PID:               9876,
-		State:             "stopped",
-		Started:           time.Now().Add(-2 * time.Hour),
-		ActiveWorkerCount: 20,
+		Status:            "stopped",
+		Started:           started2,
+		ActiveWorkerCount: 1,
 	}

 	tests := []struct {
-		processes []*base.ProcessInfo
+		processes []*base.ProcessState
+		want      []*base.ProcessInfo
 	}{
-		{processes: []*base.ProcessInfo{}},
-		{processes: []*base.ProcessInfo{ps1}},
-		{processes: []*base.ProcessInfo{ps1, ps2}},
+		{
+			processes: []*base.ProcessState{},
+			want:      []*base.ProcessInfo{},
+		},
+		{
+			processes: []*base.ProcessState{ps1},
+			want:      []*base.ProcessInfo{info1},
+		},
+		{
+			processes: []*base.ProcessState{ps1, ps2},
+			want:      []*base.ProcessInfo{info1, info2},
+		},
 	}

 	ignoreOpt := cmpopts.IgnoreUnexported(base.ProcessInfo{})
@@ -2088,7 +2107,7 @@ func TestListProcesses(t *testing.T) {
 		h.FlushDB(t, r.client)

 		for _, ps := range tc.processes {
-			if err := r.WriteProcessInfo(ps, 5*time.Second); err != nil {
+			if err := r.WriteProcessState(ps, 5*time.Second); err != nil {
 				t.Fatal(err)
 			}
 		}
@@ -2097,9 +2116,74 @@ func TestListProcesses(t *testing.T) {
 		if err != nil {
 			t.Errorf("r.ListProcesses returned an error: %v", err)
 		}
-		if diff := cmp.Diff(tc.processes, got, h.SortProcessInfoOpt, ignoreOpt); diff != "" {
+		if diff := cmp.Diff(tc.want, got, h.SortProcessInfoOpt, ignoreOpt); diff != "" {
 			t.Errorf("r.ListProcesses returned %v, want %v; (-want,+got)\n%s",
 				got, tc.processes, diff)
 		}
 	}
 }
+
+func TestListWorkers(t *testing.T) {
+	r := setup(t)
+
+	const (
+		host = "127.0.0.1"
+		pid  = 4567
+	)
+
+	m1 := h.NewTaskMessage("send_email", map[string]interface{}{"user_id": "abc123"})
+	m2 := h.NewTaskMessage("gen_thumbnail", map[string]interface{}{"path": "some/path/to/image/file"})
+	m3 := h.NewTaskMessage("reindex", map[string]interface{}{})
+	t1 := time.Now().Add(-time.Second)
+	t2 := time.Now().Add(-10 * time.Second)
+	t3 := time.Now().Add(-time.Minute)
+
+	type workerStats struct {
+		msg     *base.TaskMessage
+		started time.Time
+	}
+
+	tests := []struct {
+		workers []*workerStats
+		want    []*base.WorkerInfo
+	}{
+		{
+			workers: []*workerStats{
+				{m1, t1},
+				{m2, t2},
+				{m3, t3},
+			},
+			want: []*base.WorkerInfo{
+				{Host: host, PID: pid, ID: m1.ID, Type: m1.Type, Queue: m1.Queue, Payload: m1.Payload, Started: t1},
+				{Host: host, PID: pid, ID: m2.ID, Type: m2.Type, Queue: m2.Queue, Payload: m2.Payload, Started: t2},
+				{Host: host, PID: pid, ID: m3.ID, Type: m3.Type, Queue: m3.Queue, Payload: m3.Payload, Started: t3},
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		h.FlushDB(t, r.client)
+
+		ps := base.NewProcessState(host, pid, 10, map[string]int{"default": 1}, false)
+
+		for _, w := range tc.workers {
+			ps.AddWorkerStats(w.msg, w.started)
+		}
+
+		err := r.WriteProcessState(ps, time.Minute)
+		if err != nil {
+			t.Errorf("could not write process state to redis: %v", err)
+			continue
+		}
+
+		got, err := r.ListWorkers()
+		if err != nil {
+			t.Errorf("(*RDB).ListWorkers() returned an error: %v", err)
+			continue
+		}
+
+		if diff := cmp.Diff(tc.want, got, h.SortWorkerInfoOpt); diff != "" {
+			t.Errorf("(*RDB).ListWorkers() = %v, want = %v; (-want,+got)\n%s", got, tc.want, diff)
+		}
+	}
+}
--- a/internal/rdb/rdb.go
+++ b/internal/rdb/rdb.go
@@ -41,6 +41,14 @@ func (r *RDB) Close() error {
 	return r.client.Close()
 }

+// KEYS[1] -> asynq:queues:<qname>
+// KEYS[2] -> asynq:queues
+// ARGV[1] -> task message data
+var enqueueCmd = redis.NewScript(`
+redis.call("LPUSH", KEYS[1], ARGV[1])
+redis.call("SADD", KEYS[2], KEYS[1])
+return 1`)
+
 // Enqueue inserts the given task to the tail of the queue.
 func (r *RDB) Enqueue(msg *base.TaskMessage) error {
 	bytes, err := json.Marshal(msg)
@@ -48,23 +56,18 @@ func (r *RDB) Enqueue(msg *base.TaskMessage) error {
 		return err
 	}
 	key := base.QueueKey(msg.Queue)
-	script := redis.NewScript(`
-	redis.call("LPUSH", KEYS[1], ARGV[1])
-	redis.call("SADD", KEYS[2], KEYS[1])
-	return 1
-	`)
-	return script.Run(r.client, []string{key, base.AllQueues}, string(bytes)).Err()
+	return enqueueCmd.Run(r.client, []string{key, base.AllQueues}, bytes).Err()
 }

-// Dequeue queries given queues in order and pops a task message if there
-// is one and returns it. If all queues are empty, ErrNoProcessableTask
-// error is returned.
+// Dequeue queries given queues in order and pops a task message if there is one and returns it.
+// If all queues are empty, ErrNoProcessableTask error is returned.
 func (r *RDB) Dequeue(qnames ...string) (*base.TaskMessage, error) {
 	var data string
 	var err error
 	if len(qnames) == 1 {
 		data, err = r.dequeueSingle(base.QueueKey(qnames[0]))
 	} else {
+		// TODO(hibiken): Take keys are argument and don't compute every time
 		var keys []string
 		for _, q := range qnames {
 			keys = append(keys, base.QueueKey(q))
@@ -90,72 +93,74 @@ func (r *RDB) dequeueSingle(queue string) (data string, err error) {
 	return r.client.BRPopLPush(queue, base.InProgressQueue, time.Second).Result()
 }

+// KEYS[1] -> asynq:in_progress
+// ARGV    -> List of queues to query in order
+var dequeueCmd = redis.NewScript(`
+local res
+for _, qkey in ipairs(ARGV) do
+	res = redis.call("RPOPLPUSH", qkey, KEYS[1])
+	if res then
+		return res
+	end
+end
+return res`)
+
 func (r *RDB) dequeue(queues ...string) (data string, err error) {
 	var args []interface{}
 	for _, qkey := range queues {
 		args = append(args, qkey)
 	}
-	script := redis.NewScript(`
-	local res
-	for _, qkey in ipairs(ARGV) do
-		res = redis.call("RPOPLPUSH", qkey, KEYS[1])
-		if res then
-			return res
-		end
-	end
-	return res
-	`)
-	res, err := script.Run(r.client, []string{base.InProgressQueue}, args...).Result()
+	res, err := dequeueCmd.Run(r.client, []string{base.InProgressQueue}, args...).Result()
 	if err != nil {
 		return "", err
 	}
 	return cast.ToStringE(res)
 }

+// KEYS[1] -> asynq:in_progress
+// KEYS[2] -> asynq:processed:<yyyy-mm-dd>
+// ARGV[1] -> base.TaskMessage value
+// ARGV[2] -> stats expiration timestamp
+// Note: LREM count ZERO means "remove all elements equal to val"
+var doneCmd = redis.NewScript(`
+redis.call("LREM", KEYS[1], 0, ARGV[1]) 
+local n = redis.call("INCR", KEYS[2])
+if tonumber(n) == 1 then
+	redis.call("EXPIREAT", KEYS[2], ARGV[2])
+end
+return redis.status_reply("OK")
+`)
+
 // Done removes the task from in-progress queue to mark the task as done.
 func (r *RDB) Done(msg *base.TaskMessage) error {
 	bytes, err := json.Marshal(msg)
 	if err != nil {
 		return err
 	}
-	// Note: LREM count ZERO means "remove all elements equal to val"
-	// KEYS[1] -> asynq:in_progress
-	// KEYS[2] -> asynq:processed:<yyyy-mm-dd>
-	// ARGV[1] -> base.TaskMessage value
-	// ARGV[2] -> stats expiration timestamp
-	script := redis.NewScript(`
-	redis.call("LREM", KEYS[1], 0, ARGV[1]) 
-	local n = redis.call("INCR", KEYS[2])
-	if tonumber(n) == 1 then
-		redis.call("EXPIREAT", KEYS[2], ARGV[2])
-	end
-	return redis.status_reply("OK")
-	`)
 	now := time.Now()
 	processedKey := base.ProcessedKey(now)
 	expireAt := now.Add(statsTTL)
-	return script.Run(r.client,
+	return doneCmd.Run(r.client,
 		[]string{base.InProgressQueue, processedKey},
-		string(bytes), expireAt.Unix()).Err()
+		bytes, expireAt.Unix()).Err()
 }

-// Requeue moves the task from in-progress queue to the default
-// queue.
+// KEYS[1] -> asynq:in_progress
+// KEYS[2] -> asynq:queues:<qname>
+// ARGV[1] -> base.TaskMessage value
+// Note: Use RPUSH to push to the head of the queue.
+var requeueCmd = redis.NewScript(`
+redis.call("LREM", KEYS[1], 0, ARGV[1])
+redis.call("RPUSH", KEYS[2], ARGV[1])
+return redis.status_reply("OK")`)
+
+// Requeue moves the task from in-progress queue to the specified queue.
 func (r *RDB) Requeue(msg *base.TaskMessage) error {
 	bytes, err := json.Marshal(msg)
 	if err != nil {
 		return err
 	}
-	// Note: Use RPUSH to push to the head of the queue.
-	// KEYS[1] -> asynq:in_progress
-	// KEYS[2] -> asynq:queues:default
-	// ARGV[1] -> base.TaskMessage value
-	script := redis.NewScript(`
-	redis.call("LREM", KEYS[1], 0, ARGV[1])
-	redis.call("RPUSH", KEYS[2], ARGV[1])
-	return redis.status_reply("OK")
-	`)
-	return script.Run(r.client,
+	return requeueCmd.Run(r.client,
 		[]string{base.InProgressQueue, base.QueueKey(msg.Queue)},
 		string(bytes)).Err()
 }
@@ -171,6 +176,27 @@ func (r *RDB) Schedule(msg *base.TaskMessage, processAt time.Time) error {
 		&redis.Z{Member: string(bytes), Score: score}).Err()
 }

+// KEYS[1] -> asynq:in_progress
+// KEYS[2] -> asynq:retry
+// KEYS[3] -> asynq:processed:<yyyy-mm-dd>
+// KEYS[4] -> asynq:failure:<yyyy-mm-dd>
+// ARGV[1] -> base.TaskMessage value to remove from base.InProgressQueue queue
+// ARGV[2] -> base.TaskMessage value to add to Retry queue
+// ARGV[3] -> retry_at UNIX timestamp
+// ARGV[4] -> stats expiration timestamp
+var retryCmd = redis.NewScript(`
+redis.call("LREM", KEYS[1], 0, ARGV[1])
+redis.call("ZADD", KEYS[2], ARGV[3], ARGV[2])
+local n = redis.call("INCR", KEYS[3])
+if tonumber(n) == 1 then
+	redis.call("EXPIREAT", KEYS[3], ARGV[4])
+end
+local m = redis.call("INCR", KEYS[4])
+if tonumber(m) == 1 then
+	redis.call("EXPIREAT", KEYS[4], ARGV[4])
+end
+return redis.status_reply("OK")`)
+
 // Retry moves the task from in-progress to retry queue, incrementing retry count
 // and assigning error message to the task message.
 func (r *RDB) Retry(msg *base.TaskMessage, processAt time.Time, errMsg string) error {
@@ -185,32 +211,11 @@ func (r *RDB) Retry(msg *base.TaskMessage, processAt time.Time, errMsg string) e
 	if err != nil {
 		return err
 	}
-	// KEYS[1] -> asynq:in_progress
-	// KEYS[2] -> asynq:retry
-	// KEYS[3] -> asynq:processed:<yyyy-mm-dd>
-	// KEYS[4] -> asynq:failure:<yyyy-mm-dd>
-	// ARGV[1] -> base.TaskMessage value to remove from base.InProgressQueue queue
-	// ARGV[2] -> base.TaskMessage value to add to Retry queue
-	// ARGV[3] -> retry_at UNIX timestamp
-	// ARGV[4] -> stats expiration timestamp
-	script := redis.NewScript(`
-	redis.call("LREM", KEYS[1], 0, ARGV[1])
-	redis.call("ZADD", KEYS[2], ARGV[3], ARGV[2])
-	local n = redis.call("INCR", KEYS[3])
-	if tonumber(n) == 1 then
-		redis.call("EXPIREAT", KEYS[3], ARGV[4])
-	end
-	local m = redis.call("INCR", KEYS[4])
-	if tonumber(m) == 1 then
-		redis.call("EXPIREAT", KEYS[4], ARGV[4])
-	end
-	return redis.status_reply("OK")
-	`)
 	now := time.Now()
 	processedKey := base.ProcessedKey(now)
 	failureKey := base.FailureKey(now)
 	expireAt := now.Add(statsTTL)
-	return script.Run(r.client,
+	return retryCmd.Run(r.client,
 		[]string{base.InProgressQueue, base.RetryQueue, processedKey, failureKey},
 		string(bytesToRemove), string(bytesToAdd), processAt.Unix(), expireAt.Unix()).Err()
 }
@@ -220,6 +225,31 @@ const (
 	deadExpirationInDays = 90
 )

+// KEYS[1] -> asynq:in_progress
+// KEYS[2] -> asynq:dead
+// KEYS[3] -> asynq:processed:<yyyy-mm-dd>
+// KEYS[4] -> asynq.failure:<yyyy-mm-dd>
+// ARGV[1] -> base.TaskMessage value to remove from base.InProgressQueue queue
+// ARGV[2] -> base.TaskMessage value to add to Dead queue
+// ARGV[3] -> died_at UNIX timestamp
+// ARGV[4] -> cutoff timestamp (e.g., 90 days ago)
+// ARGV[5] -> max number of tasks in dead queue (e.g., 100)
+// ARGV[6] -> stats expiration timestamp
+var killCmd = redis.NewScript(`
+redis.call("LREM", KEYS[1], 0, ARGV[1])
+redis.call("ZADD", KEYS[2], ARGV[3], ARGV[2])
+redis.call("ZREMRANGEBYSCORE", KEYS[2], "-inf", ARGV[4])
+redis.call("ZREMRANGEBYRANK", KEYS[2], 0, -ARGV[5])
+local n = redis.call("INCR", KEYS[3])
+if tonumber(n) == 1 then
+	redis.call("EXPIREAT", KEYS[3], ARGV[6])
+end
+local m = redis.call("INCR", KEYS[4])
+if tonumber(m) == 1 then
+	redis.call("EXPIREAT", KEYS[4], ARGV[6])
+end
+return redis.status_reply("OK")`)
+
 // Kill sends the task to "dead" queue from in-progress queue, assigning
 // the error message to the task.
 // It also trims the set by timestamp and set size.
@@ -239,50 +269,27 @@ func (r *RDB) Kill(msg *base.TaskMessage, errMsg string) error {
 	processedKey := base.ProcessedKey(now)
 	failureKey := base.FailureKey(now)
 	expireAt := now.Add(statsTTL)
-	// KEYS[1] -> asynq:in_progress
-	// KEYS[2] -> asynq:dead
-	// KEYS[3] -> asynq:processed:<yyyy-mm-dd>
-	// KEYS[4] -> asynq.failure:<yyyy-mm-dd>
-	// ARGV[1] -> base.TaskMessage value to remove from base.InProgressQueue queue
-	// ARGV[2] -> base.TaskMessage value to add to Dead queue
-	// ARGV[3] -> died_at UNIX timestamp
-	// ARGV[4] -> cutoff timestamp (e.g., 90 days ago)
-	// ARGV[5] -> max number of tasks in dead queue (e.g., 100)
-	// ARGV[6] -> stats expiration timestamp
-	script := redis.NewScript(`
-	redis.call("LREM", KEYS[1], 0, ARGV[1])
-	redis.call("ZADD", KEYS[2], ARGV[3], ARGV[2])
-	redis.call("ZREMRANGEBYSCORE", KEYS[2], "-inf", ARGV[4])
-	redis.call("ZREMRANGEBYRANK", KEYS[2], 0, -ARGV[5])
-	local n = redis.call("INCR", KEYS[3])
-	if tonumber(n) == 1 then
-		redis.call("EXPIREAT", KEYS[3], ARGV[6])
-	end
-	local m = redis.call("INCR", KEYS[4])
-	if tonumber(m) == 1 then
-		redis.call("EXPIREAT", KEYS[4], ARGV[6])
-	end
-	return redis.status_reply("OK")
-	`)
-	return script.Run(r.client,
+	return killCmd.Run(r.client,
 		[]string{base.InProgressQueue, base.DeadQueue, processedKey, failureKey},
 		string(bytesToRemove), string(bytesToAdd), now.Unix(), limit, maxDeadTasks, expireAt.Unix()).Err()
 }

-// RestoreUnfinished  moves all tasks from in-progress list to the queue
+// KEYS[1] -> asynq:in_progress
+// ARGV[1] -> queue prefix
+var requeueAllCmd = redis.NewScript(`
+local msgs = redis.call("LRANGE", KEYS[1], 0, -1)
+for _, msg in ipairs(msgs) do
+	local decoded = cjson.decode(msg)
+	local qkey = ARGV[1] .. decoded["Queue"]
+	redis.call("RPUSH", qkey, msg)
+	redis.call("LREM", KEYS[1], 0, msg)
+end
+return table.getn(msgs)`)
+
+// RequeueAll moves all tasks from in-progress list to the queue
 // and reports the number of tasks restored.
-func (r *RDB) RestoreUnfinished() (int64, error) {
-	script := redis.NewScript(`
-	local msgs = redis.call("LRANGE", KEYS[1], 0, -1)
-	for _, msg in ipairs(msgs) do
-		local decoded = cjson.decode(msg)
-		local qkey = ARGV[1] .. decoded["Queue"]
-		redis.call("LREM", KEYS[1], 0, msg)
-		redis.call("RPUSH", qkey, msg)
-	end
-	return table.getn(msgs)
-	`)
-	res, err := script.Run(r.client, []string{base.InProgressQueue}, base.QueuePrefix).Result()
+func (r *RDB) RequeueAll() (int64, error) {
+	res, err := requeueAllCmd.Run(r.client, []string{base.InProgressQueue}, base.QueuePrefix).Result()
 	if err != nil {
 		return 0, err
 	}
@@ -313,86 +320,124 @@ func (r *RDB) CheckAndEnqueue(qnames ...string) error {
 	return nil
 }

+// KEYS[1] -> source queue (e.g. scheduled or retry queue)
+// ARGV[1] -> current unix time
+// ARGV[2] -> queue prefix
+var forwardCmd = redis.NewScript(`
+local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], "-inf", ARGV[1])
+for _, msg in ipairs(msgs) do
+	local decoded = cjson.decode(msg)
+	local qkey = ARGV[2] .. decoded["Queue"]
+	redis.call("LPUSH", qkey, msg)
+	redis.call("ZREM", KEYS[1], msg)
+end
+return msgs`)
+
 // forward moves all tasks with a score less than the current unix time
 // from the src zset.
 func (r *RDB) forward(src string) error {
-	script := redis.NewScript(`
-	local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], "-inf", ARGV[1])
-	for _, msg in ipairs(msgs) do
-		redis.call("ZREM", KEYS[1], msg)
-		local decoded = cjson.decode(msg)
-		local qkey = ARGV[2] .. decoded["Queue"]
-		redis.call("LPUSH", qkey, msg)
-	end
-	return msgs
-	`)
 	now := float64(time.Now().Unix())
-	return script.Run(r.client,
+	return forwardCmd.Run(r.client,
 		[]string{src}, now, base.QueuePrefix).Err()
 }

+// KEYS[1] -> source queue (e.g. scheduled or retry queue)
+// KEYS[2] -> destination queue
+var forwardSingleCmd = redis.NewScript(`
+local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], "-inf", ARGV[1])
+for _, msg in ipairs(msgs) do
+	redis.call("LPUSH", KEYS[2], msg)
+	redis.call("ZREM", KEYS[1], msg)
+end
+return msgs`)
+
 // forwardSingle moves all tasks with a score less than the current unix time
 // from the src zset to dst list.
 func (r *RDB) forwardSingle(src, dst string) error {
-	script := redis.NewScript(`
-	local msgs = redis.call("ZRANGEBYSCORE", KEYS[1], "-inf", ARGV[1])
-	for _, msg in ipairs(msgs) do
-		redis.call("ZREM", KEYS[1], msg)
-		redis.call("LPUSH", KEYS[2], msg)
-	end
-	return msgs
-	`)
 	now := float64(time.Now().Unix())
-	return script.Run(r.client,
+	return forwardSingleCmd.Run(r.client,
 		[]string{src, dst}, now).Err()
 }

-// WriteProcessInfo writes process information to redis with expiration
-// set to the value ttl.
-func (r *RDB) WriteProcessInfo(ps *base.ProcessInfo, ttl time.Duration) error {
-	bytes, err := json.Marshal(ps)
+// KEYS[1]  -> asynq:ps:<host:pid>
+// KEYS[2]  -> asynq:ps
+// KEYS[3]  -> asynq:workers<host:pid>
+// keys[4]  -> asynq:workers
+// ARGV[1]  -> expiration time
+// ARGV[2]  -> TTL in seconds
+// ARGV[3]  -> process info
+// ARGV[4:] -> alternate key-value pair of (worker id, worker data)
+// Note: Add key to ZSET with expiration time as score.
+// ref: https://github.com/antirez/redis/issues/135#issuecomment-2361996
+var writeProcessInfoCmd = redis.NewScript(`
+redis.call("SETEX", KEYS[1], ARGV[2], ARGV[3])
+redis.call("ZADD", KEYS[2], ARGV[1], KEYS[1])
+redis.call("DEL", KEYS[3])
+for i = 4, table.getn(ARGV)-1, 2 do
+	redis.call("HSET", KEYS[3], ARGV[i], ARGV[i+1])
+end
+redis.call("EXPIRE", KEYS[3], ARGV[2])
+redis.call("ZADD", KEYS[4], ARGV[1], KEYS[3])
+return redis.status_reply("OK")`)
+
+// WriteProcessState writes process state data to redis with expiration  set to the value ttl.
+func (r *RDB) WriteProcessState(ps *base.ProcessState, ttl time.Duration) error {
+	info := ps.Get()
+	bytes, err := json.Marshal(info)
 	if err != nil {
 		return err
 	}
-	// Note: Add key to ZSET with expiration time as score.
-	// ref: https://github.com/antirez/redis/issues/135#issuecomment-2361996
+	var args []interface{} // args to the lua script
 	exp := time.Now().Add(ttl).UTC()
-	key := base.ProcessInfoKey(ps.Host, ps.PID)
-	// KEYS[1] -> asynq:ps
-	// KEYS[2] -> asynq:ps:<host:pid>
-	// ARGV[1] -> expiration time
-	// ARGV[2] -> TTL in seconds
-	// ARGV[3] -> process info
-	script := redis.NewScript(`
-	redis.call("ZADD", KEYS[1], ARGV[1], KEYS[2])
-	redis.call("SETEX", KEYS[2], ARGV[2], ARGV[3])
-	return redis.status_reply("OK")
-	`)
-	return script.Run(r.client, []string{base.AllProcesses, key}, float64(exp.Unix()), ttl.Seconds(), string(bytes)).Err()
+	workers := ps.GetWorkers()
+	args = append(args, float64(exp.Unix()), ttl.Seconds(), bytes)
+	for _, w := range workers {
+		bytes, err := json.Marshal(w)
+		if err != nil {
+			continue // skip bad data
+		}
+		args = append(args, w.ID.String(), bytes)
+	}
+	pkey := base.ProcessInfoKey(info.Host, info.PID)
+	wkey := base.WorkersKey(info.Host, info.PID)
+	return writeProcessInfoCmd.Run(r.client,
+		[]string{pkey, base.AllProcesses, wkey, base.AllWorkers},
+		args...).Err()
 }

-// ReadProcessInfo reads process information stored in redis.
-func (r *RDB) ReadProcessInfo(host string, pid int) (*base.ProcessInfo, error) {
-	key := base.ProcessInfoKey(host, pid)
-	data, err := r.client.Get(key).Result()
+// KEYS[1] -> asynq:ps
+// KEYS[2] -> asynq:ps:<host:pid>
+// KEYS[3] -> asynq:workers
+// KEYS[4] -> asynq:workers<host:pid>
+var clearProcessInfoCmd = redis.NewScript(`
+redis.call("ZREM", KEYS[1], KEYS[2])
+redis.call("DEL", KEYS[2])
+redis.call("ZREM", KEYS[3], KEYS[4])
+redis.call("DEL", KEYS[4])
+return redis.status_reply("OK")`)
+
+// ClearProcessState deletes process state data from redis.
+func (r *RDB) ClearProcessState(ps *base.ProcessState) error {
+	info := ps.Get()
+	host, pid := info.Host, info.PID
+	pkey := base.ProcessInfoKey(host, pid)
+	wkey := base.WorkersKey(host, pid)
+	return clearProcessInfoCmd.Run(r.client,
+		[]string{base.AllProcesses, pkey, base.AllWorkers, wkey}).Err()
+}
+
+// CancelationPubSub returns a pubsub for cancelation messages.
+func (r *RDB) CancelationPubSub() (*redis.PubSub, error) {
+	pubsub := r.client.Subscribe(base.CancelChannel)
+	_, err := pubsub.Receive()
 	if err != nil {
 		return nil, err
 	}
-	var pinfo base.ProcessInfo
-	err = json.Unmarshal([]byte(data), &pinfo)
-	if err != nil {
-		return nil, err
-	}
-	return &pinfo, nil
+	return pubsub, nil
 }

-// ClearProcessInfo deletes process information from redis.
-func (r *RDB) ClearProcessInfo(ps *base.ProcessInfo) error {
-	key := base.ProcessInfoKey(ps.Host, ps.PID)
-	script := redis.NewScript(`
-	redis.call("ZREM", KEYS[1], KEYS[2])
-	redis.call("DEL", KEYS[2])
-	return redis.status_reply("OK")
-	`)
-	return script.Run(r.client, []string{base.AllProcesses, key}).Err()
+// PublishCancelation publish cancelation message to all subscribers.
+// The message is the ID for the task to be canceled.
+func (r *RDB) PublishCancelation(id string) error {
+	return r.client.Publish(base.CancelChannel, id).Err()
 }
--- a/internal/rdb/rdb_test.go
+++ b/internal/rdb/rdb_test.go
@@ -5,8 +5,9 @@
 package rdb

 import (
+	"encoding/json"
 	"fmt"
-	"strconv"
+	"sync"
 	"testing"
 	"time"

@@ -541,7 +542,7 @@ func TestKill(t *testing.T) {
 	}
 }

-func TestRestoreUnfinished(t *testing.T) {
+func TestRequeueAll(t *testing.T) {
 	r := setup(t)
 	t1 := h.NewTaskMessage("send_email", nil)
 	t2 := h.NewTaskMessage("export_csv", nil)
@@ -613,9 +614,9 @@ func TestRestoreUnfinished(t *testing.T) {
 			h.SeedEnqueuedQueue(t, r.client, msgs, qname)
 		}

-		got, err := r.RestoreUnfinished()
+		got, err := r.RequeueAll()
 		if got != tc.want || err != nil {
-			t.Errorf("(*RDB).RestoreUnfinished() = %v %v, want %v nil", got, err, tc.want)
+			t.Errorf("(*RDB).RequeueAll() = %v %v, want %v nil", got, err, tc.want)
 			continue
 		}

@@ -741,81 +742,278 @@ func TestCheckAndEnqueue(t *testing.T) {
 	}
 }

-func TestReadWriteClearProcessInfo(t *testing.T) {
+func TestWriteProcessState(t *testing.T) {
 	r := setup(t)
-	pinfo := &base.ProcessInfo{
-		Concurrency:       10,
-		Queues:            map[string]uint{"default": 2, "email": 5, "low": 1},
-		PID:               98765,
+	host, pid := "localhost", 98765
+	queues := map[string]int{"default": 2, "email": 5, "low": 1}
+
+	started := time.Now()
+	ps := base.NewProcessState(host, pid, 10, queues, false)
+	ps.SetStarted(started)
+	ps.SetStatus(base.StatusRunning)
+	ttl := 5 * time.Second
+
+	h.FlushDB(t, r.client)
+
+	err := r.WriteProcessState(ps, ttl)
+	if err != nil {
+		t.Errorf("r.WriteProcessState returned an error: %v", err)
+	}
+
+	// Check ProcessInfo was written correctly
+	pkey := base.ProcessInfoKey(host, pid)
+	data := r.client.Get(pkey).Val()
+	var got base.ProcessInfo
+	err = json.Unmarshal([]byte(data), &got)
+	if err != nil {
+		t.Fatalf("could not decode json: %v", err)
+	}
+	want := base.ProcessInfo{
 		Host:              "localhost",
-		State:             "running",
-		Started:           time.Now(),
-		ActiveWorkerCount: 1,
+		PID:               98765,
+		Concurrency:       10,
+		Queues:            map[string]int{"default": 2, "email": 5, "low": 1},
+		StrictPriority:    false,
+		Status:            "running",
+		Started:           started,
+		ActiveWorkerCount: 0,
+	}
+	if diff := cmp.Diff(want, got); diff != "" {
+		t.Errorf("persisted ProcessInfo was %v, want %v; (-want,+got)\n%s",
+			got, want, diff)
+	}
+	// Check ProcessInfo TTL was set correctly
+	gotTTL := r.client.TTL(pkey).Val()
+	timeCmpOpt := cmpopts.EquateApproxTime(time.Second)
+	if !cmp.Equal(ttl, gotTTL, timeCmpOpt) {
+		t.Errorf("TTL of %q was %v, want %v", pkey, gotTTL, ttl)
+	}
+	// Check ProcessInfo key was added to the set correctly
+	gotProcesses := r.client.ZRange(base.AllProcesses, 0, -1).Val()
+	wantProcesses := []string{pkey}
+	if diff := cmp.Diff(wantProcesses, gotProcesses); diff != "" {
+		t.Errorf("%q contained %v, want %v", base.AllProcesses, gotProcesses, wantProcesses)
 	}

-	tests := []struct {
-		pi  *base.ProcessInfo
-		ttl time.Duration
-	}{
-		{pinfo, 5 * time.Second},
+	// Check WorkersInfo was written correctly
+	wkey := base.WorkersKey(host, pid)
+	workerExist := r.client.Exists(wkey).Val()
+	if workerExist != 0 {
+		t.Errorf("%q key exists", wkey)
 	}
-
-	for _, tc := range tests {
-		h.FlushDB(t, r.client)
-
-		err := r.WriteProcessInfo(tc.pi, tc.ttl)
-		if err != nil {
-			t.Errorf("r.WriteProcessInfo returned an error: %v", err)
-			continue
-		}
-
-		got, err := r.ReadProcessInfo(tc.pi.Host, tc.pi.PID)
-		if err != nil {
-			t.Errorf("r.ReadProcessInfo returned an error: %v", err)
-			continue
-		}
-
-		ignoreOpt := cmpopts.IgnoreUnexported(base.ProcessInfo{})
-		if diff := cmp.Diff(tc.pi, got, ignoreOpt); diff != "" {
-			t.Errorf("r.ReadProcessInfo(%q, %d) = %+v, want %+v; (-want,+got)\n%s",
-				tc.pi.Host, tc.pi.PID, got, tc.pi, diff)
-		}
-
-		key := base.ProcessInfoKey(tc.pi.Host, tc.pi.PID)
-		gotTTL := r.client.TTL(key).Val()
-		if !cmp.Equal(tc.ttl, gotTTL, timeCmpOpt) {
-			t.Errorf("redis TTL %q returned %v, want %v", key, gotTTL, tc.ttl)
-		}
-
-		now := time.Now().UTC()
-		allKeys, err := r.client.ZRangeByScore(base.AllProcesses, &redis.ZRangeBy{
-			Min: strconv.Itoa(int(now.Unix())),
-			Max: "+inf",
-		}).Result()
-		if err != nil {
-			t.Errorf("redis ZRANGEBYSCORE %q %d +inf returned an error: %v",
-				base.AllProcesses, now.Unix(), err)
-			continue
-		}
-
-		wantAllKeys := []string{key}
-		if diff := cmp.Diff(wantAllKeys, allKeys); diff != "" {
-			t.Errorf("all keys = %v, want %v; (-want,+got)\n%s", allKeys, wantAllKeys, diff)
-		}
-
-		if err := r.ClearProcessInfo(tc.pi); err != nil {
-			t.Errorf("r.ClearProcessInfo returned an error: %v", err)
-			continue
-		}
-
-		// 1 means key exists
-		if r.client.Exists(key).Val() == 1 {
-			t.Errorf("expected %q to be deleted", key)
-		}
-
-		if r.client.ZCard(base.AllProcesses).Val() != 0 {
-			t.Errorf("expected %q to be empty", base.AllProcesses)
-		}
-
+	// Check WorkersInfo key was added to the set correctly
+	gotWorkerKeys := r.client.ZRange(base.AllWorkers, 0, -1).Val()
+	wantWorkerKeys := []string{wkey}
+	if diff := cmp.Diff(wantWorkerKeys, gotWorkerKeys); diff != "" {
+		t.Errorf("%q contained %v, want %v", base.AllWorkers, gotWorkerKeys, wantWorkerKeys)
 	}
 }
+
+func TestWriteProcessStateWithWorkers(t *testing.T) {
+	r := setup(t)
+	host, pid := "localhost", 98765
+	queues := map[string]int{"default": 2, "email": 5, "low": 1}
+	concurrency := 10
+
+	started := time.Now().Add(-10 * time.Minute)
+	w1Started := time.Now().Add(-time.Minute)
+	w2Started := time.Now().Add(-time.Second)
+	msg1 := h.NewTaskMessage("send_email", map[string]interface{}{"user_id": "123"})
+	msg2 := h.NewTaskMessage("gen_thumbnail", map[string]interface{}{"path": "some/path/to/imgfile"})
+	ps := base.NewProcessState(host, pid, concurrency, queues, false)
+	ps.SetStarted(started)
+	ps.SetStatus(base.StatusRunning)
+	ps.AddWorkerStats(msg1, w1Started)
+	ps.AddWorkerStats(msg2, w2Started)
+	ttl := 5 * time.Second
+
+	h.FlushDB(t, r.client)
+
+	err := r.WriteProcessState(ps, ttl)
+	if err != nil {
+		t.Errorf("r.WriteProcessState returned an error: %v", err)
+	}
+
+	// Check ProcessInfo was written correctly
+	pkey := base.ProcessInfoKey(host, pid)
+	data := r.client.Get(pkey).Val()
+	var got base.ProcessInfo
+	err = json.Unmarshal([]byte(data), &got)
+	if err != nil {
+		t.Fatalf("could not decode json: %v", err)
+	}
+	want := base.ProcessInfo{
+		Host:              host,
+		PID:               pid,
+		Concurrency:       concurrency,
+		Queues:            queues,
+		StrictPriority:    false,
+		Status:            "running",
+		Started:           started,
+		ActiveWorkerCount: 2,
+	}
+	if diff := cmp.Diff(want, got); diff != "" {
+		t.Errorf("persisted ProcessInfo was %v, want %v; (-want,+got)\n%s",
+			got, want, diff)
+	}
+	// Check ProcessInfo TTL was set correctly
+	gotTTL := r.client.TTL(pkey).Val()
+	timeCmpOpt := cmpopts.EquateApproxTime(time.Second)
+	if !cmp.Equal(ttl, gotTTL, timeCmpOpt) {
+		t.Errorf("TTL of %q was %v, want %v", pkey, gotTTL, ttl)
+	}
+	// Check ProcessInfo key was added to the set correctly
+	gotProcesses := r.client.ZRange(base.AllProcesses, 0, -1).Val()
+	wantProcesses := []string{pkey}
+	if diff := cmp.Diff(wantProcesses, gotProcesses); diff != "" {
+		t.Errorf("%q contained %v, want %v", base.AllProcesses, gotProcesses, wantProcesses)
+	}
+
+	// Check WorkersInfo was written correctly
+	wkey := base.WorkersKey(host, pid)
+	wdata := r.client.HGetAll(wkey).Val()
+	if len(wdata) != 2 {
+		t.Fatalf("HGETALL %q returned a hash of size %d, want 2", wkey, len(wdata))
+	}
+	gotWorkers := make(map[string]*base.WorkerInfo)
+	for key, val := range wdata {
+		var w base.WorkerInfo
+		if err := json.Unmarshal([]byte(val), &w); err != nil {
+			t.Fatalf("could not unmarshal worker's data: %v", err)
+		}
+		gotWorkers[key] = &w
+	}
+	wantWorkers := map[string]*base.WorkerInfo{
+		msg1.ID.String(): &base.WorkerInfo{
+			Host:    host,
+			PID:     pid,
+			ID:      msg1.ID,
+			Type:    msg1.Type,
+			Queue:   msg1.Queue,
+			Payload: msg1.Payload,
+			Started: w1Started,
+		},
+		msg2.ID.String(): &base.WorkerInfo{
+			Host:    host,
+			PID:     pid,
+			ID:      msg2.ID,
+			Type:    msg2.Type,
+			Queue:   msg2.Queue,
+			Payload: msg2.Payload,
+			Started: w2Started,
+		},
+	}
+	if diff := cmp.Diff(wantWorkers, gotWorkers); diff != "" {
+		t.Errorf("persisted workers info was %v, want %v; (-want,+got)\n%s",
+			gotWorkers, wantWorkers, diff)
+	}
+
+	// Check WorkersInfo TTL was set correctly
+	gotTTL = r.client.TTL(wkey).Val()
+	if !cmp.Equal(ttl, gotTTL, timeCmpOpt) {
+		t.Errorf("TTL of %q was %v, want %v", wkey, gotTTL, ttl)
+	}
+	// Check WorkersInfo key was added to the set correctly
+	gotWorkerKeys := r.client.ZRange(base.AllWorkers, 0, -1).Val()
+	wantWorkerKeys := []string{wkey}
+	if diff := cmp.Diff(wantWorkerKeys, gotWorkerKeys); diff != "" {
+		t.Errorf("%q contained %v, want %v", base.AllWorkers, gotWorkerKeys, wantWorkerKeys)
+	}
+}
+
+func TestClearProcessState(t *testing.T) {
+	r := setup(t)
+	host, pid := "127.0.0.1", 1234
+
+	h.FlushDB(t, r.client)
+
+	pkey := base.ProcessInfoKey(host, pid)
+	wkey := base.WorkersKey(host, pid)
+	otherPKey := base.ProcessInfoKey("otherhost", 12345)
+	otherWKey := base.WorkersKey("otherhost", 12345)
+	// Populate the keys.
+	if err := r.client.Set(pkey, "process-info", 0).Err(); err != nil {
+		t.Fatal(err)
+	}
+	if err := r.client.HSet(wkey, "worker-key", "worker-info").Err(); err != nil {
+		t.Fatal(err)
+	}
+	if err := r.client.ZAdd(base.AllProcesses, &redis.Z{Member: pkey}).Err(); err != nil {
+		t.Fatal(err)
+	}
+	if err := r.client.ZAdd(base.AllProcesses, &redis.Z{Member: otherPKey}).Err(); err != nil {
+		t.Fatal(err)
+	}
+	if err := r.client.ZAdd(base.AllWorkers, &redis.Z{Member: wkey}).Err(); err != nil {
+		t.Fatal(err)
+	}
+	if err := r.client.ZAdd(base.AllWorkers, &redis.Z{Member: otherWKey}).Err(); err != nil {
+		t.Fatal(err)
+	}
+
+	ps := base.NewProcessState(host, pid, 10, map[string]int{"default": 1}, false)
+
+	err := r.ClearProcessState(ps)
+	if err != nil {
+		t.Fatalf("(*RDB).ClearProcessState failed: %v", err)
+	}
+
+	// Check all keys are cleared
+	if r.client.Exists(pkey).Val() != 0 {
+		t.Errorf("Redis key %q exists", pkey)
+	}
+	if r.client.Exists(wkey).Val() != 0 {
+		t.Errorf("Redis key %q exists", wkey)
+	}
+	gotProcessKeys := r.client.ZRange(base.AllProcesses, 0, -1).Val()
+	wantProcessKeys := []string{otherPKey}
+	if diff := cmp.Diff(wantProcessKeys, gotProcessKeys); diff != "" {
+		t.Errorf("%q contained %v, want %v", base.AllProcesses, gotProcessKeys, wantProcessKeys)
+	}
+	gotWorkerKeys := r.client.ZRange(base.AllWorkers, 0, -1).Val()
+	wantWorkerKeys := []string{otherWKey}
+	if diff := cmp.Diff(wantWorkerKeys, gotWorkerKeys); diff != "" {
+		t.Errorf("%q contained %v, want %v", base.AllWorkers, gotWorkerKeys, wantWorkerKeys)
+	}
+}
+
+func TestCancelationPubSub(t *testing.T) {
+	r := setup(t)
+
+	pubsub, err := r.CancelationPubSub()
+	if err != nil {
+		t.Fatalf("(*RDB).CancelationPubSub() returned an error: %v", err)
+	}
+
+	cancelCh := pubsub.Channel()
+
+	var (
+		mu       sync.Mutex
+		received []string
+	)
+
+	go func() {
+		for msg := range cancelCh {
+			mu.Lock()
+			received = append(received, msg.Payload)
+			mu.Unlock()
+		}
+	}()
+
+	publish := []string{"one", "two", "three"}
+
+	for _, msg := range publish {
+		r.PublishCancelation(msg)
+	}
+
+	// allow for message to reach subscribers.
+	time.Sleep(time.Second)
+
+	pubsub.Close()
+
+	mu.Lock()
+	if diff := cmp.Diff(publish, received, h.SortStringSliceOpt); diff != "" {
+		t.Errorf("subscriber received %v, want %v; (-want,+got)\n%s", received, publish, diff)
+	}
+	mu.Unlock()
+}
--- a/processor.go
+++ b/processor.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"context"
 	"fmt"
 	"math/rand"
 	"sort"
@@ -19,11 +20,11 @@ import (
 type processor struct {
 	rdb *rdb.RDB

-	pinfo *base.ProcessInfo
+	ps *base.ProcessState

 	handler Handler

-	queueConfig map[string]uint
+	queueConfig map[string]int

 	// orderedQueues is set only in strict-priority mode.
 	orderedQueues []string
@@ -50,30 +51,35 @@ type processor struct {

 	// quit channel communicates to the in-flight worker goroutines to stop.
 	quit chan struct{}
+
+	// cancelations is a set of cancel functions for all in-progress tasks.
+	cancelations *base.Cancelations
 }

 type retryDelayFunc func(n int, err error, task *Task) time.Duration

 // newProcessor constructs a new processor.
-func newProcessor(r *rdb.RDB, pinfo *base.ProcessInfo, fn retryDelayFunc, syncRequestCh chan<- *syncRequest) *processor {
-	qcfg := normalizeQueueCfg(pinfo.Queues)
+func newProcessor(r *rdb.RDB, ps *base.ProcessState, fn retryDelayFunc, syncCh chan<- *syncRequest, c *base.Cancelations) *processor {
+	info := ps.Get()
+	qcfg := normalizeQueueCfg(info.Queues)
 	orderedQueues := []string(nil)
-	if pinfo.StrictPriority {
+	if info.StrictPriority {
 		orderedQueues = sortByPriority(qcfg)
 	}
 	return &processor{
 		rdb:            r,
-		pinfo:          pinfo,
+		ps:             ps,
 		queueConfig:    qcfg,
 		orderedQueues:  orderedQueues,
 		retryDelayFunc: fn,
-		syncRequestCh:  syncRequestCh,
+		syncRequestCh:  syncCh,
+		cancelations:   c,
 		errLogLimiter:  rate.NewLimiter(rate.Every(3*time.Second), 1),
-		sema:           make(chan struct{}, pinfo.Concurrency),
+		sema:           make(chan struct{}, info.Concurrency),
 		done:           make(chan struct{}),
 		abort:          make(chan struct{}),
 		quit:           make(chan struct{}),
-		handler:        HandlerFunc(func(t *Task) error { return fmt.Errorf("handler not set") }),
+		handler:        HandlerFunc(func(ctx context.Context, t *Task) error { return fmt.Errorf("handler not set") }),
 	}
 }

@@ -98,6 +104,12 @@ func (p *processor) terminate() {
 	const timeout = 8 * time.Second
 	time.AfterFunc(timeout, func() { close(p.quit) })
 	logger.info("Waiting for all workers to finish...")
+
+	// send cancellation signal to all in-progress task handlers
+	for _, cancel := range p.cancelations.GetAll() {
+		cancel()
+	}
+
 	// block until all workers have released the token
 	for i := 0; i < cap(p.sema); i++ {
 		p.sema <- struct{}{}
@@ -106,11 +118,13 @@ func (p *processor) terminate() {
 	p.restore() // move any unfinished tasks back to the queue.
 }

-func (p *processor) start() {
+func (p *processor) start(wg *sync.WaitGroup) {
 	// NOTE: The call to "restore" needs to complete before starting
 	// the processor goroutine.
 	p.restore()
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		for {
 			select {
 			case <-p.done:
@@ -151,17 +165,20 @@ func (p *processor) exec() {
 		p.requeue(msg)
 		return
 	case p.sema <- struct{}{}: // acquire token
-		p.pinfo.IncrActiveWorkerCount(1)
+		p.ps.AddWorkerStats(msg, time.Now())
 		go func() {
 			defer func() {
+				p.ps.DeleteWorkerStats(msg)
 				<-p.sema /* release token */
-				p.pinfo.IncrActiveWorkerCount(-1)
 			}()

 			resCh := make(chan error, 1)
 			task := NewTask(msg.Type, msg.Payload)
+			ctx, cancel := createContext(msg)
+			p.cancelations.Add(msg.ID.String(), cancel)
 			go func() {
-				resCh <- perform(p.handler, task)
+				resCh <- perform(ctx, task, p.handler)
+				p.cancelations.Delete(msg.ID.String())
 			}()

 			select {
@@ -191,7 +208,7 @@ func (p *processor) exec() {
 // restore moves all tasks from "in-progress" back to queue
 // to restore all unfinished tasks.
 func (p *processor) restore() {
-	n, err := p.rdb.RestoreUnfinished()
+	n, err := p.rdb.RequeueAll()
 	if err != nil {
 		logger.error("Could not restore unfinished tasks: %v", err)
 	}
@@ -282,13 +299,13 @@ func (p *processor) queues() []string {
 // perform calls the handler with the given task.
 // If the call returns without panic, it simply returns the value,
 // otherwise, it recovers from panic and returns an error.
-func perform(h Handler, task *Task) (err error) {
+func perform(ctx context.Context, task *Task, h Handler) (err error) {
 	defer func() {
 		if x := recover(); x != nil {
 			err = fmt.Errorf("panic: %v", x)
 		}
 	}()
-	return h.ProcessTask(task)
+	return h.ProcessTask(ctx, task)
 }

 // uniq dedupes elements and returns a slice of unique names of length l.
@@ -310,7 +327,7 @@ func uniq(names []string, l int) []string {

 // sortByPriority returns a list of queue names sorted by
 // their priority level in descending order.
-func sortByPriority(qcfg map[string]uint) []string {
+func sortByPriority(qcfg map[string]int) []string {
 	var queues []*queue
 	for qname, n := range qcfg {
 		queues = append(queues, &queue{qname, n})
@@ -325,7 +342,7 @@ func sortByPriority(qcfg map[string]uint) []string {

 type queue struct {
 	name     string
-	priority uint
+	priority int
 }

 type byPriority []*queue
@@ -336,21 +353,21 @@ func (x byPriority) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }

 // normalizeQueueCfg divides priority numbers by their
 // greatest common divisor.
-func normalizeQueueCfg(queueCfg map[string]uint) map[string]uint {
-	var xs []uint
+func normalizeQueueCfg(queueCfg map[string]int) map[string]int {
+	var xs []int
 	for _, x := range queueCfg {
 		xs = append(xs, x)
 	}
 	d := gcd(xs...)
-	res := make(map[string]uint)
+	res := make(map[string]int)
 	for q, x := range queueCfg {
 		res[q] = x / d
 	}
 	return res
 }

-func gcd(xs ...uint) uint {
-	fn := func(x, y uint) uint {
+func gcd(xs ...int) int {
+	fn := func(x, y int) int {
 		for y > 0 {
 			x, y = y, x%y
 		}
@@ -365,3 +382,16 @@ func gcd(xs ...uint) uint {
 	}
 	return res
 }
+
+// createContext returns a context and cancel function for a given task message.
+func createContext(msg *base.TaskMessage) (context.Context, context.CancelFunc) {
+	timeout, err := time.ParseDuration(msg.Timeout)
+	if err != nil {
+		logger.error("cannot parse timeout duration for %+v", msg)
+		return context.WithCancel(context.Background())
+	}
+	if timeout == 0 {
+		return context.WithCancel(context.Background())
+	}
+	return context.WithTimeout(context.Background(), timeout)
+}
--- a/processor_test.go
+++ b/processor_test.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"context"
 	"fmt"
 	"sort"
 	"sync"
@@ -59,17 +60,21 @@ func TestProcessorSuccess(t *testing.T) {
 		// instantiate a new processor
 		var mu sync.Mutex
 		var processed []*Task
-		handler := func(task *Task) error {
+		handler := func(ctx context.Context, task *Task) error {
 			mu.Lock()
 			defer mu.Unlock()
 			processed = append(processed, task)
 			return nil
 		}
-		pi := base.NewProcessInfo("localhost", 1234, 10, defaultQueueConfig, false)
-		p := newProcessor(rdbClient, pi, defaultDelayFunc, nil)
+		workerCh := make(chan int)
+		go fakeHeartbeater(workerCh)
+		ps := base.NewProcessState("localhost", 1234, 10, defaultQueueConfig, false)
+		cancelations := base.NewCancelations()
+		p := newProcessor(rdbClient, ps, defaultDelayFunc, nil, cancelations)
 		p.handler = HandlerFunc(handler)

-		p.start()
+		var wg sync.WaitGroup
+		p.start(&wg)
 		for _, msg := range tc.incoming {
 			err := rdbClient.Enqueue(msg)
 			if err != nil {
@@ -79,6 +84,7 @@ func TestProcessorSuccess(t *testing.T) {
 		}
 		time.Sleep(tc.wait)
 		p.terminate()
+		close(workerCh)

 		if diff := cmp.Diff(tc.wantProcessed, processed, sortTaskOpt, cmp.AllowUnexported(Payload{})); diff != "" {
 			t.Errorf("mismatch found in processed tasks; (-want, +got)\n%s", diff)
@@ -146,14 +152,18 @@ func TestProcessorRetry(t *testing.T) {
 		delayFunc := func(n int, e error, t *Task) time.Duration {
 			return tc.delay
 		}
-		handler := func(task *Task) error {
+		handler := func(ctx context.Context, task *Task) error {
 			return fmt.Errorf(errMsg)
 		}
-		pi := base.NewProcessInfo("localhost", 1234, 10, defaultQueueConfig, false)
-		p := newProcessor(rdbClient, pi, delayFunc, nil)
+		workerCh := make(chan int)
+		go fakeHeartbeater(workerCh)
+		ps := base.NewProcessState("localhost", 1234, 10, defaultQueueConfig, false)
+		cancelations := base.NewCancelations()
+		p := newProcessor(rdbClient, ps, delayFunc, nil, cancelations)
 		p.handler = HandlerFunc(handler)

-		p.start()
+		var wg sync.WaitGroup
+		p.start(&wg)
 		for _, msg := range tc.incoming {
 			err := rdbClient.Enqueue(msg)
 			if err != nil {
@@ -163,6 +173,7 @@ func TestProcessorRetry(t *testing.T) {
 		}
 		time.Sleep(tc.wait)
 		p.terminate()
+		close(workerCh)

 		cmpOpt := cmpopts.EquateApprox(0, float64(time.Second)) // allow up to second difference in zset score
 		gotRetry := h.GetRetryEntries(t, r)
@@ -189,11 +200,11 @@ func TestProcessorQueues(t *testing.T) {
 	})

 	tests := []struct {
-		queueCfg map[string]uint
+		queueCfg map[string]int
 		want     []string
 	}{
 		{
-			queueCfg: map[string]uint{
+			queueCfg: map[string]int{
 				"high":    6,
 				"default": 3,
 				"low":     1,
@@ -201,7 +212,7 @@ func TestProcessorQueues(t *testing.T) {
 			want: []string{"high", "default", "low"},
 		},
 		{
-			queueCfg: map[string]uint{
+			queueCfg: map[string]int{
 				"default": 1,
 			},
 			want: []string{"default"},
@@ -209,8 +220,9 @@ func TestProcessorQueues(t *testing.T) {
 	}

 	for _, tc := range tests {
-		pi := base.NewProcessInfo("localhost", 1234, 10, tc.queueCfg, false)
-		p := newProcessor(nil, pi, defaultDelayFunc, nil)
+		cancelations := base.NewCancelations()
+		ps := base.NewProcessState("localhost", 1234, 10, tc.queueCfg, false)
+		p := newProcessor(nil, ps, defaultDelayFunc, nil, cancelations)
 		got := p.queues()
 		if diff := cmp.Diff(tc.want, got, sortOpt); diff != "" {
 			t.Errorf("with queue config: %v\n(*processor).queues() = %v, want %v\n(-want,+got):\n%s",
@@ -264,25 +276,30 @@ func TestProcessorWithStrictPriority(t *testing.T) {
 		// instantiate a new processor
 		var mu sync.Mutex
 		var processed []*Task
-		handler := func(task *Task) error {
+		handler := func(ctx context.Context, task *Task) error {
 			mu.Lock()
 			defer mu.Unlock()
 			processed = append(processed, task)
 			return nil
 		}
-		queueCfg := map[string]uint{
+		queueCfg := map[string]int{
 			"critical":            3,
 			base.DefaultQueueName: 2,
 			"low":                 1,
 		}
 		// Note: Set concurrency to 1 to make sure tasks are processed one at a time.
-		pi := base.NewProcessInfo("localhost", 1234, 1 /*concurrency */, queueCfg, true /* strict */)
-		p := newProcessor(rdbClient, pi, defaultDelayFunc, nil)
+		workerCh := make(chan int)
+		go fakeHeartbeater(workerCh)
+		cancelations := base.NewCancelations()
+		ps := base.NewProcessState("localhost", 1234, 1 /* concurrency */, queueCfg, true /*strict*/)
+		p := newProcessor(rdbClient, ps, defaultDelayFunc, nil, cancelations)
 		p.handler = HandlerFunc(handler)

-		p.start()
+		var wg sync.WaitGroup
+		p.start(&wg)
 		time.Sleep(tc.wait)
 		p.terminate()
+		close(workerCh)

 		if diff := cmp.Diff(tc.wantProcessed, processed, cmp.AllowUnexported(Payload{})); diff != "" {
 			t.Errorf("mismatch found in processed tasks; (-want, +got)\n%s", diff)
@@ -303,7 +320,7 @@ func TestPerform(t *testing.T) {
 	}{
 		{
 			desc: "handler returns nil",
-			handler: func(t *Task) error {
+			handler: func(ctx context.Context, t *Task) error {
 				return nil
 			},
 			task:    NewTask("gen_thumbnail", map[string]interface{}{"src": "some/img/path"}),
@@ -311,7 +328,7 @@ func TestPerform(t *testing.T) {
 		},
 		{
 			desc: "handler returns error",
-			handler: func(t *Task) error {
+			handler: func(ctx context.Context, t *Task) error {
 				return fmt.Errorf("something went wrong")
 			},
 			task:    NewTask("gen_thumbnail", map[string]interface{}{"src": "some/img/path"}),
@@ -319,7 +336,7 @@ func TestPerform(t *testing.T) {
 		},
 		{
 			desc: "handler panics",
-			handler: func(t *Task) error {
+			handler: func(ctx context.Context, t *Task) error {
 				panic("something went terribly wrong")
 			},
 			task:    NewTask("gen_thumbnail", map[string]interface{}{"src": "some/img/path"}),
@@ -328,7 +345,7 @@ func TestPerform(t *testing.T) {
 	}

 	for _, tc := range tests {
-		got := perform(tc.handler, tc.task)
+		got := perform(context.Background(), tc.task, tc.handler)
 		if !tc.wantErr && got != nil {
 			t.Errorf("%s: perform() = %v, want nil", tc.desc, got)
 			continue
@@ -339,3 +356,9 @@ func TestPerform(t *testing.T) {
 		}
 	}
 }
+
+// fake heartbeater to receive sends from the worker channel.
+func fakeHeartbeater(ch <-chan int) {
+	for range ch {
+	}
+}
--- a/scheduler.go
+++ b/scheduler.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"sync"
 	"time"

 	"github.com/hibiken/asynq/internal/rdb"
@@ -23,7 +24,7 @@ type scheduler struct {
 	qnames []string
 }

-func newScheduler(r *rdb.RDB, avgInterval time.Duration, qcfg map[string]uint) *scheduler {
+func newScheduler(r *rdb.RDB, avgInterval time.Duration, qcfg map[string]int) *scheduler {
 	var qnames []string
 	for q := range qcfg {
 		qnames = append(qnames, q)
@@ -43,8 +44,10 @@ func (s *scheduler) terminate() {
 }

 // start starts the "scheduler" goroutine.
-func (s *scheduler) start() {
+func (s *scheduler) start(wg *sync.WaitGroup) {
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		for {
 			select {
 			case <-s.done:
--- a/scheduler_test.go
+++ b/scheduler_test.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"sync"
 	"testing"
 	"time"

@@ -69,7 +70,8 @@ func TestScheduler(t *testing.T) {
 		h.SeedRetryQueue(t, r, tc.initRetry)         // initialize retry queue
 		h.SeedEnqueuedQueue(t, r, tc.initQueue)      // initialize default queue

-		s.start()
+		var wg sync.WaitGroup
+		s.start(&wg)
 		time.Sleep(tc.wait)
 		s.terminate()

--- a/subscriber.go
+++ b/subscriber.go
@@ -0,0 +1,62 @@
+// Copyright 2020 Kentaro Hibino. All rights reserved.
+// Use of this source code is governed by a MIT license
+// that can be found in the LICENSE file.
+
+package asynq
+
+import (
+	"sync"
+
+	"github.com/hibiken/asynq/internal/base"
+	"github.com/hibiken/asynq/internal/rdb"
+)
+
+type subscriber struct {
+	rdb *rdb.RDB
+
+	// channel to communicate back to the long running "subscriber" goroutine.
+	done chan struct{}
+
+	// cancelations hold cancel functions for all in-progress tasks.
+	cancelations *base.Cancelations
+}
+
+func newSubscriber(rdb *rdb.RDB, cancelations *base.Cancelations) *subscriber {
+	return &subscriber{
+		rdb:          rdb,
+		done:         make(chan struct{}),
+		cancelations: cancelations,
+	}
+}
+
+func (s *subscriber) terminate() {
+	logger.info("Subscriber shutting down...")
+	// Signal the subscriber goroutine to stop.
+	s.done <- struct{}{}
+}
+
+func (s *subscriber) start(wg *sync.WaitGroup) {
+	pubsub, err := s.rdb.CancelationPubSub()
+	cancelCh := pubsub.Channel()
+	if err != nil {
+		logger.error("cannot subscribe to cancelation channel: %v", err)
+		return
+	}
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			select {
+			case <-s.done:
+				pubsub.Close()
+				logger.info("Subscriber done")
+				return
+			case msg := <-cancelCh:
+				cancel, ok := s.cancelations.Get(msg.Payload)
+				if ok {
+					cancel()
+				}
+			}
+		}
+	}()
+}
--- a/subscriber_test.go
+++ b/subscriber_test.go
@@ -0,0 +1,64 @@
+// Copyright 2020 Kentaro Hibino. All rights reserved.
+// Use of this source code is governed by a MIT license
+// that can be found in the LICENSE file.
+
+package asynq
+
+import (
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/hibiken/asynq/internal/base"
+	"github.com/hibiken/asynq/internal/rdb"
+)
+
+func TestSubscriber(t *testing.T) {
+	r := setup(t)
+	rdbClient := rdb.NewRDB(r)
+
+	tests := []struct {
+		registeredID string // ID for which cancel func is registered
+		publishID    string // ID to be published
+		wantCalled   bool   // whether cancel func should be called
+	}{
+		{"abc123", "abc123", true},
+		{"abc456", "abc123", false},
+	}
+
+	for _, tc := range tests {
+		var mu sync.Mutex
+		called := false
+		fakeCancelFunc := func() {
+			mu.Lock()
+			defer mu.Unlock()
+			called = true
+		}
+		cancelations := base.NewCancelations()
+		cancelations.Add(tc.registeredID, fakeCancelFunc)
+
+		subscriber := newSubscriber(rdbClient, cancelations)
+		var wg sync.WaitGroup
+		subscriber.start(&wg)
+
+		if err := rdbClient.PublishCancelation(tc.publishID); err != nil {
+			subscriber.terminate()
+			t.Fatalf("could not publish cancelation message: %v", err)
+		}
+
+		// allow for redis to publish message
+		time.Sleep(time.Second)
+
+		mu.Lock()
+		if called != tc.wantCalled {
+			if tc.wantCalled {
+				t.Errorf("fakeCancelFunc was not called, want the function to be called")
+			} else {
+				t.Errorf("fakeCancelFunc was called, want the function to not be called")
+			}
+		}
+		mu.Unlock()
+
+		subscriber.terminate()
+	}
+}
--- a/syncer.go
+++ b/syncer.go
@@ -5,6 +5,7 @@
 package asynq

 import (
+	"sync"
 	"time"
 )

@@ -39,8 +40,10 @@ func (s *syncer) terminate() {
 	s.done <- struct{}{}
 }

-func (s *syncer) start() {
+func (s *syncer) start(wg *sync.WaitGroup) {
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		var requests []*syncRequest
 		for {
 			select {
--- a/syncer_test.go
+++ b/syncer_test.go
@@ -5,10 +5,11 @@
 package asynq

 import (
+	"fmt"
+	"sync"
 	"testing"
 	"time"

-	"github.com/go-redis/redis/v7"
 	h "github.com/hibiken/asynq/internal/asynqtest"
 	"github.com/hibiken/asynq/internal/base"
 	"github.com/hibiken/asynq/internal/rdb"
@@ -27,7 +28,8 @@ func TestSyncer(t *testing.T) {
 	const interval = time.Second
 	syncRequestCh := make(chan *syncRequest)
 	syncer := newSyncer(syncRequestCh, interval)
-	syncer.start()
+	var wg sync.WaitGroup
+	syncer.start(&wg)
 	defer syncer.terminate()

 	for _, msg := range inProgress {
@@ -48,53 +50,43 @@ func TestSyncer(t *testing.T) {
 }

 func TestSyncerRetry(t *testing.T) {
-	inProgress := []*base.TaskMessage{
-		h.NewTaskMessage("send_email", nil),
-		h.NewTaskMessage("reindex", nil),
-		h.NewTaskMessage("gen_thumbnail", nil),
-	}
-	goodClient := setup(t)
-	h.SeedInProgressQueue(t, goodClient, inProgress)
-
-	// Simulate the situation where redis server is down
-	// by connecting to a wrong port.
-	badClient := redis.NewClient(&redis.Options{
-		Addr: "localhost:6390",
-	})
-	rdbClient := rdb.NewRDB(badClient)
-
 	const interval = time.Second
 	syncRequestCh := make(chan *syncRequest)
 	syncer := newSyncer(syncRequestCh, interval)
-	syncer.start()
+
+	var wg sync.WaitGroup
+	syncer.start(&wg)
 	defer syncer.terminate()

-	for _, msg := range inProgress {
-		m := msg
-		syncRequestCh <- &syncRequest{
-			fn: func() error {
-				return rdbClient.Done(m)
-			},
+	var (
+		mu      sync.Mutex
+		counter int
+	)
+
+	// Increment the counter for each call.
+	// Initial call will fail and second call will succeed.
+	requestFunc := func() error {
+		mu.Lock()
+		defer mu.Unlock()
+		if counter == 0 {
+			counter++
+			return fmt.Errorf("zero")
 		}
+		counter++
+		return nil
 	}

-	time.Sleep(2 * interval) // ensure that syncer runs at least once
-
-	// Sanity check to ensure that message was not successfully deleted
-	// from in-progress list.
-	gotInProgress := h.GetInProgressMessages(t, goodClient)
-	if l := len(gotInProgress); l != len(inProgress) {
-		t.Errorf("%q has length %d; want %d", base.InProgressQueue, l, len(inProgress))
+	syncRequestCh <- &syncRequest{
+		fn:     requestFunc,
+		errMsg: "error",
 	}

-	// FIXME: This assignment introduces data race and running the test with -race will fail.
-	// simualate failover.
-	rdbClient = rdb.NewRDB(goodClient)
+	// allow syncer to retry
+	time.Sleep(3 * interval)

-	time.Sleep(2 * interval) // ensure that syncer runs at least once
-
-	gotInProgress = h.GetInProgressMessages(t, goodClient)
-	if l := len(gotInProgress); l != 0 {
-		t.Errorf("%q has length %d; want 0", base.InProgressQueue, l)
+	mu.Lock()
+	if counter != 2 {
+		t.Errorf("counter = %d, want 2", counter)
 	}
+	mu.Unlock()
 }
--- a/tools/asynqmon/README.md
+++ b/tools/asynqmon/README.md
@@ -8,10 +8,12 @@ Asynqmon is a command line tool to monitor the tasks managed by `asynq` package.
 - [Quick Start](#quick-start)
  - [Stats](#stats)
  - [History](#history)
+  - [Process Status](#process-status)
  - [List](#list)
  - [Enqueue](#enqueue)
  - [Delete](#delete)
  - [Kill](#kill)
+  - [Cancel](#cancel)
 - [Config File](#config-file)

 ## Installation
@@ -22,7 +24,7 @@ In order to use the tool, compile it using the following command:

 This will create the asynqmon executable under your `$GOPATH/bin` directory.

-## Quick Start
+## Quickstart

 The tool has a few commands to inspect the state of tasks and queues.

@@ -56,6 +58,16 @@ Example:

 ![Gif](/docs/assets/asynqmon_history.gif)

+### Process Status
+
+PS (ProcessStatus) command shows the list of running worker processes.
+
+Example:
+
+    asynqmon ps
+
+![Gif](/docs/assets/asynqmon_ps.gif)
+
 ### List

 List command shows all tasks in the specified state in a table format
@@ -122,6 +134,18 @@ Example:

 Running the above command will move all **Retry** tasks to **Dead** state.

+### Cancel
+
+Command `cancel` takes a task ID and sends a cancelation signal to the goroutine processing the specified task.  
+You can obtain the task ID by running `ls` command.
+
+The task should be in "in-progress" state.
+Handler implementation needs to be context aware in order to actually stop processing.
+
+Example:
+
+    asynqmon cancel bnogo8gt6toe23vhef0g
+
 ## Config File

 You can use a config file to set default values for the flags.
--- a/tools/asynqmon/cmd/cancel.go
+++ b/tools/asynqmon/cmd/cancel.go
@@ -0,0 +1,53 @@
+// Copyright 2020 Kentaro Hibino. All rights reserved.
+// Use of this source code is governed by a MIT license
+// that can be found in the LICENSE file.
+
+package cmd
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/go-redis/redis/v7"
+	"github.com/hibiken/asynq/internal/rdb"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+// cancelCmd represents the cancel command
+var cancelCmd = &cobra.Command{
+	Use:   "cancel [task id]",
+	Short: "Sends a cancelation signal to the goroutine processing the specified task",
+	Long: `Cancel (asynqmon cancel) will send a cancelation signal to the goroutine processing 
+the specified task. 
+
+The command takes one argument which specifies the task to cancel.
+The task should be in in-progress state.
+Identifier for a task should be obtained by running "asynqmon ls" command.
+
+Handler implementation needs to be context aware for cancelation signal to
+actually cancel the processing.
+
+Example: asynqmon cancel bnogo8gt6toe23vhef0g`,
+	Args: cobra.ExactArgs(1),
+	Run:  cancel,
+}
+
+func init() {
+	rootCmd.AddCommand(cancelCmd)
+}
+
+func cancel(cmd *cobra.Command, args []string) {
+	r := rdb.NewRDB(redis.NewClient(&redis.Options{
+		Addr:     viper.GetString("uri"),
+		DB:       viper.GetInt("db"),
+		Password: viper.GetString("password"),
+	}))
+
+	err := r.PublishCancelation(args[0])
+	if err != nil {
+		fmt.Printf("could not send cancelation signal: %v\n", err)
+		os.Exit(1)
+	}
+	fmt.Printf("Successfully sent cancelation siganl for task %s\n", args[0])
+}
--- a/tools/asynqmon/cmd/ls.go
+++ b/tools/asynqmon/cmd/ls.go
@@ -44,16 +44,24 @@ asynqmon ls enqueued:critical -> List tasks from critical queue
 }

 // Flags
-var pageSize uint
-var pageNum uint
+var pageSize int
+var pageNum int

 func init() {
 	rootCmd.AddCommand(lsCmd)
-	lsCmd.Flags().UintVar(&pageSize, "size", 30, "page size")
-	lsCmd.Flags().UintVar(&pageNum, "page", 0, "page number - zero indexed (default 0)")
+	lsCmd.Flags().IntVar(&pageSize, "size", 30, "page size")
+	lsCmd.Flags().IntVar(&pageNum, "page", 0, "page number - zero indexed (default 0)")
 }

 func ls(cmd *cobra.Command, args []string) {
+	if pageSize < 0 {
+		fmt.Println("page size cannot be negative.")
+		os.Exit(1)
+	}
+	if pageNum < 0 {
+		fmt.Println("page number cannot be negative.")
+		os.Exit(1)
+	}
 	c := redis.NewClient(&redis.Options{
 		Addr:     viper.GetString("uri"),
 		DB:       viper.GetInt("db"),
@@ -184,11 +192,16 @@ func listRetry(r *rdb.RDB) {
 		fmt.Println("No retry tasks")
 		return
 	}
-	cols := []string{"ID", "Type", "Payload", "Retry In", "Last Error", "Retried", "Max Retry", "Queue"}
+	cols := []string{"ID", "Type", "Payload", "Next Retry", "Last Error", "Retried", "Max Retry", "Queue"}
 	printRows := func(w io.Writer, tmpl string) {
 		for _, t := range tasks {
-			retryIn := fmt.Sprintf("%.0f seconds", t.ProcessAt.Sub(time.Now()).Seconds())
-			fmt.Fprintf(w, tmpl, queryID(t.ID, t.Score, "r"), t.Type, t.Payload, retryIn, t.ErrorMsg, t.Retried, t.Retry, t.Queue)
+			var nextRetry string
+			if d := t.ProcessAt.Sub(time.Now()); d > 0 {
+				nextRetry = fmt.Sprintf("in %v", d.Round(time.Second))
+			} else {
+				nextRetry = "right now"
+			}
+			fmt.Fprintf(w, tmpl, queryID(t.ID, t.Score, "r"), t.Type, t.Payload, nextRetry, t.ErrorMsg, t.Retried, t.Retry, t.Queue)
 		}
 	}
 	printTable(cols, printRows)
--- a/tools/asynqmon/cmd/ps.go
+++ b/tools/asynqmon/cmd/ps.go
@@ -73,7 +73,7 @@ func ps(cmd *cobra.Command, args []string) {
 	printRows := func(w io.Writer, tmpl string) {
 		for _, ps := range processes {
 			fmt.Fprintf(w, tmpl,
-				ps.Host, ps.PID, ps.State,
+				ps.Host, ps.PID, ps.Status,
 				fmt.Sprintf("%d/%d", ps.ActiveWorkerCount, ps.Concurrency),
 				formatQueues(ps.Queues), timeAgo(ps.Started))
 		}
@@ -87,11 +87,11 @@ func timeAgo(since time.Time) string {
 	return fmt.Sprintf("%v ago", d)
 }

-func formatQueues(qmap map[string]uint) string {
+func formatQueues(qmap map[string]int) string {
 	// sort queues by priority and name
 	type queue struct {
 		name     string
-		priority uint
+		priority int
 	}
 	var queues []*queue
 	for qname, p := range qmap {
--- a/tools/asynqmon/cmd/workers.go
+++ b/tools/asynqmon/cmd/workers.go
@@ -0,0 +1,75 @@
+// Copyright 2020 Kentaro Hibino. All rights reserved.
+// Use of this source code is governed by a MIT license
+// that can be found in the LICENSE file.
+
+package cmd
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"sort"
+
+	"github.com/go-redis/redis/v7"
+	"github.com/hibiken/asynq/internal/rdb"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+// workersCmd represents the workers command
+var workersCmd = &cobra.Command{
+	Use:   "workers",
+	Short: "Shows all running workers information",
+	Long: `Workers (asynqmon workers) will show all running workers information.
+
+The command shows the follwoing for each worker:
+* Process in which the worker is running
+* ID of the task worker is processing
+* Type of the task worker is processing
+* Payload of the task worker is processing
+* Queue that the task was pulled from.
+* Time the worker started processing the task`,
+	Args: cobra.NoArgs,
+	Run:  workers,
+}
+
+func init() {
+	rootCmd.AddCommand(workersCmd)
+}
+
+func workers(cmd *cobra.Command, args []string) {
+	r := rdb.NewRDB(redis.NewClient(&redis.Options{
+		Addr:     viper.GetString("uri"),
+		DB:       viper.GetInt("db"),
+		Password: viper.GetString("password"),
+	}))
+
+	workers, err := r.ListWorkers()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	if len(workers) == 0 {
+		fmt.Println("No workers")
+		return
+	}
+
+	// sort by started timestamp or ID.
+	sort.Slice(workers, func(i, j int) bool {
+		x, y := workers[i], workers[j]
+		if x.Started != y.Started {
+			return x.Started.Before(y.Started)
+		}
+		return x.ID.String() < y.ID.String()
+	})
+
+	cols := []string{"Process", "ID", "Type", "Payload", "Queue", "Started"}
+	printRows := func(w io.Writer, tmpl string) {
+		for _, wk := range workers {
+			fmt.Fprintf(w, tmpl,
+				fmt.Sprintf("%s:%d", wk.Host, wk.PID), wk.ID, wk.Type, wk.Payload, wk.Queue, timeAgo(wk.Started))
+		}
+	}
+	printTable(cols, printRows)
+}
--- a/tools/go.mod
+++ b/tools/go.mod
@@ -0,0 +1,14 @@
+module github.com/hibiken/asynq/tools
+
+go 1.13
+
+require (
+	github.com/go-redis/redis/v7 v7.2.0
+	github.com/hibiken/asynq v0.4.0
+	github.com/mitchellh/go-homedir v1.1.0
+	github.com/rs/xid v1.2.1
+	github.com/spf13/cobra v0.0.5
+	github.com/spf13/viper v1.6.2
+)
+
+replace github.com/hibiken/asynq => ./..
--- a/tools/go.sum
+++ b/tools/go.sum
@@ -0,0 +1,195 @@
+cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
+github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
+github.com/armon/consul-api v0.0.0-20180202201655-eb2c6b5be1b6/go.mod h1:grANhF5doyWs3UAsr3K4I6qtAmlQcZDesFNEHPZAzj8=
+github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
+github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
+github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
+github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
+github.com/coreos/bbolt v1.3.2/go.mod h1:iRUV2dpdMOn7Bo10OQBFzIJO9kkE559Wcmn+qkEiiKk=
+github.com/coreos/etcd v3.3.10+incompatible/go.mod h1:uF7uidLiAD3TWHmW31ZFd/JWoc32PjwdhPthX9715RE=
+github.com/coreos/go-etcd v2.0.0+incompatible/go.mod h1:Jez6KQU2B/sWsbdaef3ED8NzMklzPG4d5KIOhIy30Tk=
+github.com/coreos/go-semver v0.2.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3EedlOD2RNk=
+github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
+github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
+github.com/cpuguy83/go-md2man v1.0.10/go.mod h1:SmD6nW6nTyfqj6ABTjUi3V3JVMnlJmwcJI5acqYI6dE=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
+github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
+github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
+github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
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Author	SHA1	Message	Date
Ken Hibino	93ff4e4149	v0.5.0	2020-02-23 20:44:44 -08:00
Ken Hibino	3ee97f327e	[ci skip] Update readme	2020-02-23 20:44:44 -08:00
Ken Hibino	49c117f4d1	Change Client APIs Use `Enqueue`, `EnqueueAt`, and `EnqueueIn` to enqueue and schedule tasks. `Schedule` method was removed.	2020-02-23 20:40:40 -08:00
Ken Hibino	5b53a2aee9	Update redis package to v7.2.0	2020-02-22 21:21:55 -08:00
Ken Hibino	26e399bc9c	Add workers command to asynqmon	2020-02-22 21:21:55 -08:00
Ken Hibino	e21fe3bd79	Add ListWorkers to RDB	2020-02-22 21:21:55 -08:00
Ken Hibino	37c6c73d9b	Add test for cancelation pubsub	2020-02-22 15:16:24 -08:00
Ken Hibino	5775a5818d	Update WriteProcessState to write both ProcessInfo and WorkerInfo to redis	2020-02-22 08:56:51 -08:00
Ken Hibino	e3c9aae8c7	Include worker stats to ProcessState	2020-02-22 08:56:51 -08:00
Ken Hibino	9e02a91808	Add workers key in base package	2020-02-22 08:56:51 -08:00
Ken Hibino	830020eb39	Add ProcessState type to base package	2020-02-22 08:56:51 -08:00
Ken Hibino	f9a6c6156f	[ci skip] Add codecov badge in readme	2020-02-19 21:37:54 -08:00
Ken Hibino	8540172306	Update travis.yml to upload coverage report to codecov	2020-02-19 21:27:40 -08:00
Ken Hibino	b44908fefd	Move tools to its own go module	2020-02-17 21:55:55 -08:00
Ken Hibino	e78d5e4171	Enable the race detector in CI builds	2020-02-16 21:25:10 -08:00
Ken Hibino	0cc486a975	Fix data race in syncer test	2020-02-16 21:25:10 -08:00
Ken Hibino	906f231e6c	Fix data race in subscriber test	2020-02-16 18:22:59 -08:00
Ken Hibino	39f237899b	Clean up heartbeater test	2020-02-16 18:22:59 -08:00
Ken Hibino	3d9a222bb3	Use sync.WaitGroup for shutdown	2020-02-16 18:22:59 -08:00
Ken Hibino	2bcaea52ce	Make heartbeater goroutine a monitor goroutine for process info.	2020-02-16 18:22:59 -08:00
Ken Hibino	0856ef32e0	v0.4.0	2020-02-13 06:25:27 -08:00
Ken Hibino	70efb7b455	[ci skip] Update changelog	2020-02-13 06:23:51 -08:00
Ken Hibino	d33ca98648	Use int as priority value type. Do not use unsigned int for merely non-negative quantities as it complicates simple arithmetic.	2020-02-13 06:23:51 -08:00
Ken Hibino	bf31fcc3ec	[ci skip] Update readme and changelog	2020-02-13 06:23:51 -08:00
Ken Hibino	cd55a0e316	Add cancel command to asynqmon cli	2020-02-13 06:23:51 -08:00
Ken Hibino	6685827147	Add redis pubsub subscriber for cancelation	2020-02-13 06:23:51 -08:00
Ken Hibino	133bb6c2c6	Update docs for context and timeout	2020-02-13 06:23:51 -08:00
Ken Hibino	39459b4412	Allow user to specify timeout per task	2020-02-13 06:23:51 -08:00
Ken Hibino	6e14062325	Send cancellation signal to all in-progress handlers on shutdown	2020-02-13 06:23:51 -08:00
Ken Hibino	1b41c721b4	Change Handler interface to take context.Context	2020-02-13 06:23:51 -08:00
Ken Hibino	79a04e52a3	[cip skip] Add link to intro video in readme	2020-02-09 10:59:32 -08:00
Ken Hibino	d9327cf24b	Avoid creating script struct on every rdb method invocation	2020-02-09 09:34:41 -08:00
Ken Hibino	7e33c9ebe0	[ci skip] Add contribution doc	2020-02-08 09:48:04 -08:00
Ken Hibino	a6b79eb7a0	[ci skip] Update readme	2020-02-07 06:45:36 -08:00
Ken Hibino	7af69c8d3c	[ci skip] Fix comments	2020-02-06 20:46:59 -08:00
Ken Hibino	6dd4c688f4	[ci skip] Update readme	2020-02-05 22:12:26 -08:00
Ken Hibino	024cfa9fe6	Update output text for task's next retry value	2020-02-05 22:12:26 -08:00