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303 lines
11 KiB
Markdown
303 lines
11 KiB
Markdown
# Asynq
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[](https://travis-ci.com/hibiken/asynq)
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[](https://opensource.org/licenses/MIT)
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[](https://goreportcard.com/report/github.com/hibiken/asynq)
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[](https://godoc.org/github.com/hibiken/asynq)
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[](https://gitter.im/go-asynq/community)
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[](https://codecov.io/gh/hibiken/asynq)
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## Overview
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Asynq is a 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.
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Highlevel overview of how Asynq works:
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- Client puts task on a queue
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- Server pulls task off queues and starts a worker goroutine for each task
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- Tasks are processed concurrently by multiple workers
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Task queues are used as a mechanism to distribute work across multiple machines.
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A system can consist of multiple worker servers and brokers, giving way to high availability and horizontal scaling.
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## Stability and Compatibility
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**Important Note**: Current major version is zero (v0.x.x) to accomodate rapid development and fast iteration while getting early feedback from users (Feedback on APIs are appreciated!). The public API could change without a major version update before v1.0.0 release.
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**Status**: The library is currently undergoing heavy development with frequent, breaking API changes.
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## Features
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- Guaranteed [at least one execution](https://www.cloudcomputingpatterns.org/at_least_once_delivery/) of a task
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- Scheduling of tasks
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- Durability since tasks are written to Redis
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- [Retries](https://github.com/hibiken/asynq/wiki/Task-Retry) of failed tasks
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- Automatic recovery of tasks in the event of a worker crash
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- [Weighted priority queues](https://github.com/hibiken/asynq/wiki/Priority-Queues#weighted-priority-queues)
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- [Strict priority queues](https://github.com/hibiken/asynq/wiki/Priority-Queues#strict-priority-queues)
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- Low latency to add a task since writes are fast in Redis
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- De-duplication of tasks using [unique option](https://github.com/hibiken/asynq/wiki/Unique-Tasks)
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- Allow [timeout and deadline per task](https://github.com/hibiken/asynq/wiki/Task-Timeout-and-Cancelation)
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- [Flexible handler interface with support for middlewares](https://github.com/hibiken/asynq/wiki/Handler-Deep-Dive)
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- [Ability to pause queue](/tools/asynq/README.md#pause) to stop processing tasks from the queue
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- [Support Redis Sentinels](https://github.com/hibiken/asynq/wiki/Automatic-Failover) for HA
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- [CLI](#command-line-tool) to inspect and remote-control queues and tasks
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## Quickstart
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First, make sure you are running a Redis server locally.
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```sh
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$ redis-server
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```
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Next, write a package that encapsulates task creation and task handling.
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```go
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package tasks
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import (
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"fmt"
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"github.com/hibiken/asynq"
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)
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// A list of task types.
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const (
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EmailDelivery = "email:deliver"
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ImageProcessing = "image:process"
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)
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//----------------------------------------------
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// Write a function NewXXXTask to create a task.
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// A task consists of a type and a payload.
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//----------------------------------------------
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func NewEmailDeliveryTask(userID int, tmplID string) *asynq.Task {
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payload := map[string]interface{}{"user_id": userID, "template_id": tmplID}
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return asynq.NewTask(EmailDelivery, payload)
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}
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func NewImageProcessingTask(src, dst string) *asynq.Task {
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payload := map[string]interface{}{"src": src, "dst": dst}
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return asynq.NewTask(ImageProcessing, payload)
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}
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//---------------------------------------------------------------
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// Write a function HandleXXXTask to handle the input task.
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// Note that it satisfies the asynq.HandlerFunc interface.
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//
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// Handler doesn't need to be a function. You can define a type
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// that satisfies asynq.Handler interface. See examples below.
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//---------------------------------------------------------------
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func HandleEmailDeliveryTask(ctx context.Context, t *asynq.Task) error {
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userID, err := t.Payload.GetInt("user_id")
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if err != nil {
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return err
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}
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tmplID, err := t.Payload.GetString("template_id")
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if err != nil {
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return err
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}
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fmt.Printf("Send Email to User: user_id = %d, template_id = %s\n", userID, tmplID)
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// Email delivery logic ...
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return nil
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}
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// ImageProcessor implements asynq.Handler interface.
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type ImageProcesser struct {
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// ... fields for struct
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}
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func (p *ImageProcessor) ProcessTask(ctx context.Context, t *asynq.Task) error {
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src, err := t.Payload.GetString("src")
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if err != nil {
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return err
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}
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dst, err := t.Payload.GetString("dst")
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if err != nil {
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return err
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}
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fmt.Printf("Process image: src = %s, dst = %s\n", src, dst)
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// Image processing logic ...
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return nil
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}
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func NewImageProcessor() *ImageProcessor {
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// ... return an instance
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}
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```
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In your web application code, import the above package and use [`Client`](https://pkg.go.dev/github.com/hibiken/asynq?tab=doc#Client) to put tasks on the queue.
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// TODO: This description needs to be updated.
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A task will be processed asynchronously by a background worker as soon as the task gets enqueued.
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Scheduled tasks will be stored in Redis and will be enqueued at the specified time.
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```go
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package main
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import (
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"time"
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"github.com/hibiken/asynq"
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"your/app/package/tasks"
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)
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const redisAddr = "127.0.0.1:6379"
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func main() {
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r := asynq.RedisClientOpt{Addr: redisAddr}
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c := asynq.NewClient(r)
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defer c.Close()
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// ------------------------------------------------------
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// Example 1: Enqueue task to be processed immediately.
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// Use (*Client).Enqueue method.
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// ------------------------------------------------------
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t := tasks.NewEmailDeliveryTask(42, "some:template:id")
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res, err := c.Enqueue(t)
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if err != nil {
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log.Fatal("could not enqueue task: %v", err)
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}
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fmt.Printf("Enqueued Result: %+v\n", res)
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// ------------------------------------------------------------
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// Example 2: Schedule task to be processed in the future.
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// Use (*Client).EnqueueIn or (*Client).EnqueueAt.
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// ------------------------------------------------------------
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t = tasks.NewEmailDeliveryTask(42, "other:template:id")
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res, err = c.EnqueueIn(24*time.Hour, t)
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if err != nil {
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log.Fatal("could not schedule task: %v", err)
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}
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fmt.Printf("Enqueued Result: %+v\n", res)
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// ----------------------------------------------------------------------------
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// Example 3: Set options to tune task processing behavior.
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// Options include MaxRetry, Queue, Timeout, Deadline, Unique etc.
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// ----------------------------------------------------------------------------
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c.SetDefaultOptions(tasks.ImageProcessing, asynq.MaxRetry(10), asynq.Timeout(time.Minute))
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t = tasks.NewImageProcessingTask("some/blobstore/url", "other/blobstore/url")
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res, err = c.Enqueue(t)
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if err != nil {
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log.Fatal("could not enqueue task: %v", err)
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}
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fmt.Printf("Enqueued Result: %+v\n", res)
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// ---------------------------------------------------------------------------
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// Example 4: Pass options to tune task processing behavior at enqueue time.
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// Options passed at enqueue time override default ones, if any.
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// ---------------------------------------------------------------------------
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t = tasks.NewImageProcessingTask("some/blobstore/url", "other/blobstore/url")
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res, err = c.Enqueue(t, asynq.Queue("critical"), asynq.Timeout(30*time.Second))
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if err != nil {
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log.Fatal("could not enqueue task: %v", err)
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}
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fmt.Printf("Enqueued Result: %+v\n", res)
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}
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```
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Next, create a worker server to process these tasks in the background.
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To start the background workers, use [`Server`](https://pkg.go.dev/github.com/hibiken/asynq?tab=doc#Server) and provide your [`Handler`](https://pkg.go.dev/github.com/hibiken/asynq?tab=doc#Handler) to process the tasks.
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You can optionally use [`ServeMux`](https://pkg.go.dev/github.com/hibiken/asynq?tab=doc#ServeMux) to create a handler, just as you would with [`"net/http"`](https://golang.org/pkg/net/http/) Handler.
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```go
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package main
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import (
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"log"
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"github.com/hibiken/asynq"
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"your/app/package/tasks"
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)
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const redisAddr = "127.0.0.1:6379"
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func main() {
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r := asynq.RedisClientOpt{Addr: redisAddr}
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srv := asynq.NewServer(r, asynq.Config{
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// Specify how many concurrent workers to use
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Concurrency: 10,
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// Optionally specify multiple queues with different priority.
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Queues: map[string]int{
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"critical": 6,
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"default": 3,
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"low": 1,
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},
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// See the godoc for other configuration options
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})
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// mux maps a type to a handler
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mux := asynq.NewServeMux()
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mux.HandleFunc(tasks.EmailDelivery, tasks.HandleEmailDeliveryTask)
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mux.Handle(tasks.ImageProcessing, tasks.NewImageProcessor())
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// ...register other handlers...
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if err := srv.Run(mux); err != nil {
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log.Fatalf("could not run server: %v", err)
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}
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}
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```
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For a more detailed walk-through of the library, see our [Getting Started Guide](https://github.com/hibiken/asynq/wiki/Getting-Started).
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To Learn more about `asynq` features and APIs, see our [Wiki](https://github.com/hibiken/asynq/wiki) and [godoc](https://godoc.org/github.com/hibiken/asynq).
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## Command Line Tool
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Asynq ships with a command line tool to inspect the state of queues and tasks.
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Here's an example of running the `stats` command.
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For details on how to use the tool, refer to the tool's [README](/tools/asynq/README.md).
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## Installation
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To install `asynq` library, run the following command:
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```sh
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go get -u github.com/hibiken/asynq
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```
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To install the CLI tool, run the following command:
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```sh
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go get -u github.com/hibiken/asynq/tools/asynq
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```
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## Requirements
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| Dependency | Version |
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| -------------------------- | ------- |
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| [Redis](https://redis.io/) | v2.8+ |
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| [Go](https://golang.org/) | v1.13+ |
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## Contributing
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We are open to, and grateful for, any contributions (Github issues/pull-requests, feedback on Gitter channel, etc) made by the community.
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Please see the [Contribution Guide](/CONTRIBUTING.md) before contributing.
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## Acknowledgements
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- [Sidekiq](https://github.com/mperham/sidekiq) : Many of the design ideas are taken from sidekiq and its Web UI
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- [RQ](https://github.com/rq/rq) : Client APIs are inspired by rq library.
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- [Cobra](https://github.com/spf13/cobra) : Asynq CLI is built with cobra
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## License
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Asynq is released under the MIT license. See [LICENSE](https://github.com/hibiken/asynq/blob/master/LICENSE).
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