asynq/internal/rdb/inspect.go

// 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 rdb

import (
	"encoding/json"
	"fmt"
	"sort"
	"strings"
	"time"

	"github.com/go-redis/redis/v7"
	"github.com/hibiken/asynq/internal/base"
	"github.com/rs/xid"
	"github.com/spf13/cast"
)

// Stats represents a state of queues at a certain time.
type Stats struct {
	Enqueued   int
	InProgress int
	Scheduled  int
	Retry      int
	Dead       int
	Processed  int
	Failed     int
	Queues     []*Queue
	Timestamp  time.Time
}

// Queue represents a task queue.
type Queue struct {
	// Name of the queue (e.g. "default", "critical").
	// Note: It doesn't include the prefix "asynq:queues:".
	Name string

	// Paused indicates whether the queue is paused.
	// If true, tasks in the queue should not be processed.
	Paused bool

	// Size is the number of tasks in the queue.
	Size int
}

// DailyStats holds aggregate data for a given day.
type DailyStats struct {
	Processed int
	Failed    int
	Time      time.Time
}

// EnqueuedTask is a task in a queue and is ready to be processed.
type EnqueuedTask struct {
	ID      xid.ID
	Type    string
	Payload map[string]interface{}
	Queue   string
}

// InProgressTask is a task that's currently being processed.
type InProgressTask struct {
	ID      xid.ID
	Type    string
	Payload map[string]interface{}
}

// ScheduledTask is a task that's scheduled to be processed in the future.
type ScheduledTask struct {
	ID        xid.ID
	Type      string
	Payload   map[string]interface{}
	ProcessAt time.Time
	Score     int64
	Queue     string
}

// RetryTask is a task that's in retry queue because worker failed to process the task.
type RetryTask struct {
	ID      xid.ID
	Type    string
	Payload map[string]interface{}
	// TODO(hibiken): add LastFailedAt time.Time
	ProcessAt time.Time
	ErrorMsg  string
	Retried   int
	Retry     int
	Score     int64
	Queue     string
}

// DeadTask is a task in that has exhausted all retries.
type DeadTask struct {
	ID           xid.ID
	Type         string
	Payload      map[string]interface{}
	LastFailedAt time.Time
	ErrorMsg     string
	Score        int64
	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) {
	now := time.Now()
	res, err := currentStatsCmd.Run(r.client, []string{
		base.AllQueues,
		base.InProgressQueue,
		base.ScheduledQueue,
		base.RetryQueue,
		base.DeadQueue,
		base.ProcessedKey(now),
		base.FailureKey(now),
	}).Result()
	if err != nil {
		return nil, err
	}
	data, err := cast.ToSliceE(res)
	if err != nil {
		return nil, err
	}
	paused, err := r.client.SMembersMap(base.PausedQueues).Result()
	if err != nil {
		return nil, err
	}
	stats := &Stats{
		Queues:    make([]*Queue, 0),
		Timestamp: now,
	}
	for i := 0; i < len(data); i += 2 {
		key := cast.ToString(data[i])
		val := cast.ToInt(data[i+1])

		switch {
		case strings.HasPrefix(key, base.QueuePrefix):
			stats.Enqueued += val
			q := Queue{
				Name: strings.TrimPrefix(key, base.QueuePrefix),
				Size: val,
			}
			if _, exist := paused[key]; exist {
				q.Paused = true
			}
			stats.Queues = append(stats.Queues, &q)
		case key == base.InProgressQueue:
			stats.InProgress = val
		case key == base.ScheduledQueue:
			stats.Scheduled = val
		case key == base.RetryQueue:
			stats.Retry = val
		case key == base.DeadQueue:
			stats.Dead = val
		case key == "processed":
			stats.Processed = val
		case key == "failed":
			stats.Failed = val
		}
	}
	sort.Slice(stats.Queues, func(i, j int) bool {
		return stats.Queues[i].Name < stats.Queues[j].Name
	})
	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 {
		return []*DailyStats{}, nil
	}
	const day = 24 * time.Hour
	now := time.Now().UTC()
	var days []time.Time
	var keys []string
	for i := 0; i < n; i++ {
		ts := now.Add(-time.Duration(i) * day)
		days = append(days, ts)
		keys = append(keys, base.ProcessedKey(ts))
		keys = append(keys, base.FailureKey(ts))
	}
	res, err := historicalStatsCmd.Run(r.client, keys, len(keys)).Result()
	if err != nil {
		return nil, err
	}
	data, err := cast.ToIntSliceE(res)
	if err != nil {
		return nil, err
	}
	var stats []*DailyStats
	for i := 0; i < len(data); i += 2 {
		stats = append(stats, &DailyStats{
			Processed: data[i],
			Failed:    data[i+1],
			Time:      days[i/2],
		})
	}
	return stats, nil
}

// RedisInfo returns a map of redis info.
func (r *RDB) RedisInfo() (map[string]string, error) {
	res, err := r.client.Info().Result()
	if err != nil {
		return nil, err
	}
	info := make(map[string]string)
	lines := strings.Split(res, "\r\n")
	for _, l := range lines {
		kv := strings.Split(l, ":")
		if len(kv) == 2 {
			info[kv[0]] = kv[1]
		}
	}
	return info, nil
}

func reverse(x []string) {
	for i := len(x)/2 - 1; i >= 0; i-- {
		opp := len(x) - 1 - i
		x[i], x[opp] = x[opp], x[i]
	}
}

// Pagination specifies the page size and page number
// for the list operation.
type Pagination struct {
	// Number of items in the page.
	Size int

	// Page number starting from zero.
	Page int
}

func (p Pagination) start() int64 {
	return int64(p.Size * p.Page)
}

func (p Pagination) stop() int64 {
	return int64(p.Size*p.Page + p.Size - 1)
}

// ListEnqueued returns enqueued tasks that are ready to be processed.
func (r *RDB) ListEnqueued(qname string, pgn Pagination) ([]*EnqueuedTask, error) {
	qkey := base.QueueKey(qname)
	if !r.client.SIsMember(base.AllQueues, qkey).Val() {
		return nil, fmt.Errorf("queue %q does not exist", qname)
	}
	// Note: Because we use LPUSH to redis list, we need to calculate the
	// correct range and reverse the list to get the tasks with pagination.
	stop := -pgn.start() - 1
	start := -pgn.stop() - 1
	data, err := r.client.LRange(qkey, start, stop).Result()
	if err != nil {
		return nil, err
	}
	reverse(data)
	var tasks []*EnqueuedTask
	for _, s := range data {
		var msg base.TaskMessage
		err := json.Unmarshal([]byte(s), &msg)
		if err != nil {
			continue // bad data, ignore and continue
		}
		tasks = append(tasks, &EnqueuedTask{
			ID:      msg.ID,
			Type:    msg.Type,
			Payload: msg.Payload,
			Queue:   msg.Queue,
		})
	}
	return tasks, nil
}

// ListInProgress returns all tasks that are currently being processed.
func (r *RDB) ListInProgress(pgn Pagination) ([]*InProgressTask, error) {
	// Note: Because we use LPUSH to redis list, we need to calculate the
	// correct range and reverse the list to get the tasks with pagination.
	stop := -pgn.start() - 1
	start := -pgn.stop() - 1
	data, err := r.client.LRange(base.InProgressQueue, start, stop).Result()
	if err != nil {
		return nil, err
	}
	reverse(data)
	var tasks []*InProgressTask
	for _, s := range data {
		var msg base.TaskMessage
		err := json.Unmarshal([]byte(s), &msg)
		if err != nil {
			continue // bad data, ignore and continue
		}
		tasks = append(tasks, &InProgressTask{
			ID:      msg.ID,
			Type:    msg.Type,
			Payload: msg.Payload,
		})
	}
	return tasks, nil
}

// ListScheduled returns all tasks that are scheduled to be processed
// in the future.
func (r *RDB) ListScheduled(pgn Pagination) ([]*ScheduledTask, error) {
	data, err := r.client.ZRangeWithScores(base.ScheduledQueue, pgn.start(), pgn.stop()).Result()
	if err != nil {
		return nil, err
	}
	var tasks []*ScheduledTask
	for _, z := range data {
		s, ok := z.Member.(string)
		if !ok {
			continue // bad data, ignore and continue
		}
		var msg base.TaskMessage
		err := json.Unmarshal([]byte(s), &msg)
		if err != nil {
			continue // bad data, ignore and continue
		}
		processAt := time.Unix(int64(z.Score), 0)
		tasks = append(tasks, &ScheduledTask{
			ID:        msg.ID,
			Type:      msg.Type,
			Payload:   msg.Payload,
			Queue:     msg.Queue,
			ProcessAt: processAt,
			Score:     int64(z.Score),
		})
	}
	return tasks, nil
}

// ListRetry returns all tasks that have failed before and willl be retried
// in the future.
func (r *RDB) ListRetry(pgn Pagination) ([]*RetryTask, error) {
	data, err := r.client.ZRangeWithScores(base.RetryQueue, pgn.start(), pgn.stop()).Result()
	if err != nil {
		return nil, err
	}
	var tasks []*RetryTask
	for _, z := range data {
		s, ok := z.Member.(string)
		if !ok {
			continue // bad data, ignore and continue
		}
		var msg base.TaskMessage
		err := json.Unmarshal([]byte(s), &msg)
		if err != nil {
			continue // bad data, ignore and continue
		}
		processAt := time.Unix(int64(z.Score), 0)
		tasks = append(tasks, &RetryTask{
			ID:        msg.ID,
			Type:      msg.Type,
			Payload:   msg.Payload,
			ErrorMsg:  msg.ErrorMsg,
			Retry:     msg.Retry,
			Retried:   msg.Retried,
			Queue:     msg.Queue,
			ProcessAt: processAt,
			Score:     int64(z.Score),
		})
	}
	return tasks, nil
}

// ListDead returns all tasks that have exhausted its retry limit.
func (r *RDB) ListDead(pgn Pagination) ([]*DeadTask, error) {
	data, err := r.client.ZRangeWithScores(base.DeadQueue, pgn.start(), pgn.stop()).Result()
	if err != nil {
		return nil, err
	}
	var tasks []*DeadTask
	for _, z := range data {
		s, ok := z.Member.(string)
		if !ok {
			continue // bad data, ignore and continue
		}
		var msg base.TaskMessage
		err := json.Unmarshal([]byte(s), &msg)
		if err != nil {
			continue // bad data, ignore and continue
		}
		lastFailedAt := time.Unix(int64(z.Score), 0)
		tasks = append(tasks, &DeadTask{
			ID:           msg.ID,
			Type:         msg.Type,
			Payload:      msg.Payload,
			ErrorMsg:     msg.ErrorMsg,
			Queue:        msg.Queue,
			LastFailedAt: lastFailedAt,
			Score:        int64(z.Score),
		})
	}
	return tasks, nil
}

// EnqueueDeadTask finds a task that matches the given id and score from dead queue
// and enqueues it for processing. If a task that matches the id and score
// does not exist, it returns ErrTaskNotFound.
func (r *RDB) EnqueueDeadTask(id xid.ID, score int64) error {
	n, err := r.removeAndEnqueue(base.DeadQueue, id.String(), float64(score))
	if err != nil {
		return err
	}
	if n == 0 {
		return ErrTaskNotFound
	}
	return nil
}

// EnqueueRetryTask finds a task that matches the given id and score from retry queue
// and enqueues it for processing. If a task that matches the id and score
// does not exist, it returns ErrTaskNotFound.
func (r *RDB) EnqueueRetryTask(id xid.ID, score int64) error {
	n, err := r.removeAndEnqueue(base.RetryQueue, id.String(), float64(score))
	if err != nil {
		return err
	}
	if n == 0 {
		return ErrTaskNotFound
	}
	return nil
}

// EnqueueScheduledTask finds a task that matches the given id and score from scheduled queue
// and enqueues it for processing. If a task that matches the id and score does not
// exist, it returns ErrTaskNotFound.
func (r *RDB) EnqueueScheduledTask(id xid.ID, score int64) error {
	n, err := r.removeAndEnqueue(base.ScheduledQueue, id.String(), float64(score))
	if err != nil {
		return err
	}
	if n == 0 {
		return ErrTaskNotFound
	}
	return nil
}

// EnqueueAllScheduledTasks enqueues all tasks from scheduled queue
// and returns the number of tasks enqueued.
func (r *RDB) EnqueueAllScheduledTasks() (int64, error) {
	return r.removeAndEnqueueAll(base.ScheduledQueue)
}

// EnqueueAllRetryTasks enqueues all tasks from retry queue
// and returns the number of tasks enqueued.
func (r *RDB) EnqueueAllRetryTasks() (int64, error) {
	return r.removeAndEnqueueAll(base.RetryQueue)
}

// EnqueueAllDeadTasks enqueues all tasks from dead queue
// and returns the number of tasks enqueued.
func (r *RDB) EnqueueAllDeadTasks() (int64, error) {
	return r.removeAndEnqueueAll(base.DeadQueue)
}

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
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
	}
	n, ok := res.(int64)
	if !ok {
		return 0, fmt.Errorf("could not cast %v to int64", res)
	}
	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) {
	res, err := removeAndEnqueueAllCmd.Run(r.client, []string{zset}, base.QueuePrefix).Result()
	if err != nil {
		return 0, err
	}
	n, ok := res.(int64)
	if !ok {
		return 0, fmt.Errorf("could not cast %v to int64", res)
	}
	return n, nil
}

// KillRetryTask finds a task that matches the given id and score from retry queue
// and moves it to dead queue. If a task that maches the id and score does not exist,
// it returns ErrTaskNotFound.
func (r *RDB) KillRetryTask(id xid.ID, score int64) error {
	n, err := r.removeAndKill(base.RetryQueue, id.String(), float64(score))
	if err != nil {
		return err
	}
	if n == 0 {
		return ErrTaskNotFound
	}
	return nil
}

// KillScheduledTask finds a task that matches the given id and score from scheduled queue
// and moves it to dead queue. If a task that maches the id and score does not exist,
// it returns ErrTaskNotFound.
func (r *RDB) KillScheduledTask(id xid.ID, score int64) error {
	n, err := r.removeAndKill(base.ScheduledQueue, id.String(), float64(score))
	if err != nil {
		return err
	}
	if n == 0 {
		return ErrTaskNotFound
	}
	return nil
}

// KillAllRetryTasks moves all tasks from retry queue to dead queue and
// returns the number of tasks that were moved.
func (r *RDB) KillAllRetryTasks() (int64, error) {
	return r.removeAndKillAll(base.RetryQueue)
}

// KillAllScheduledTasks moves all tasks from scheduled queue to dead queue and
// returns the number of tasks that were moved.
func (r *RDB) KillAllScheduledTasks() (int64, error) {
	return r.removeAndKillAll(base.ScheduledQueue)
}

// 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
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 := removeAndKillCmd.Run(r.client,
		[]string{zset, base.DeadQueue},
		score, id, now.Unix(), limit, maxDeadTasks).Result()
	if err != nil {
		return 0, err
	}
	n, ok := res.(int64)
	if !ok {
		return 0, fmt.Errorf("could not cast %v to int64", res)
	}
	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) {
	now := time.Now()
	limit := now.AddDate(0, 0, -deadExpirationInDays).Unix() // 90 days ago
	res, err := removeAndKillAllCmd.Run(r.client, []string{zset, base.DeadQueue},
		now.Unix(), limit, maxDeadTasks).Result()
	if err != nil {
		return 0, err
	}
	n, ok := res.(int64)
	if !ok {
		return 0, fmt.Errorf("could not cast %v to int64", res)
	}
	return n, nil
}

// DeleteDeadTask finds a task that matches the given id and score from dead queue
// and deletes it. If a task that matches the id and score does not exist,
// it returns ErrTaskNotFound.
func (r *RDB) DeleteDeadTask(id xid.ID, score int64) error {
	return r.deleteTask(base.DeadQueue, id.String(), float64(score))
}

// DeleteRetryTask finds a task that matches the given id and score from retry queue
// and deletes it. If a task that matches the id and score does not exist,
// it returns ErrTaskNotFound.
func (r *RDB) DeleteRetryTask(id xid.ID, score int64) error {
	return r.deleteTask(base.RetryQueue, id.String(), float64(score))
}

// DeleteScheduledTask finds a task that matches the given id and score from
// scheduled queue  and deletes it. If a task that matches the id and score
//does not exist, it returns ErrTaskNotFound.
func (r *RDB) DeleteScheduledTask(id xid.ID, score int64) error {
	return r.deleteTask(base.ScheduledQueue, id.String(), float64(score))
}

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
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
	}
	n, ok := res.(int64)
	if !ok {
		return fmt.Errorf("could not cast %v to int64", res)
	}
	if n == 0 {
		return ErrTaskNotFound
	}
	return nil
}

// DeleteAllDeadTasks deletes all tasks from the dead queue.
func (r *RDB) DeleteAllDeadTasks() error {
	return r.client.Del(base.DeadQueue).Err()
}

// DeleteAllRetryTasks deletes all tasks from the dead queue.
func (r *RDB) DeleteAllRetryTasks() error {
	return r.client.Del(base.RetryQueue).Err()
}

// DeleteAllScheduledTasks deletes all tasks from the dead queue.
func (r *RDB) DeleteAllScheduledTasks() error {
	return r.client.Del(base.ScheduledQueue).Err()
}

// ErrQueueNotFound indicates specified queue does not exist.
type ErrQueueNotFound struct {
	qname string
}

func (e *ErrQueueNotFound) Error() string {
	return fmt.Sprintf("queue %q does not exist", e.qname)
}

// ErrQueueNotEmpty indicates specified queue is not empty.
type ErrQueueNotEmpty struct {
	qname string
}

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
// of whether the queue is empty.
// If force is set to false, it will only remove the queue if
// it is empty.
func (r *RDB) RemoveQueue(qname string, force bool) error {
	var script *redis.Script
	if force {
		script = removeQueueForceCmd
	} else {
		script = removeQueueCmd
	}
	err := script.Run(r.client,
		[]string{base.AllQueues, base.QueueKey(qname)},
		force).Err()
	if err != nil {
		switch err.Error() {
		case "LIST NOT FOUND":
			return &ErrQueueNotFound{qname}
		case "LIST NOT EMPTY":
			return &ErrQueueNotEmpty{qname}
		default:
			return err
		}
	}
	return nil
}

// Note: Script also removes stale keys.
var listServersCmd = 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 s = redis.call("GET", key)
	if s then
		table.insert(res, s)
	end  
end
redis.call("ZREMRANGEBYSCORE", KEYS[1], "-inf", now-1)
return res`)

// ListServers returns the list of server info.
func (r *RDB) ListServers() ([]*base.ServerInfo, error) {
	res, err := listServersCmd.Run(r.client,
		[]string{base.AllServers}, time.Now().UTC().Unix()).Result()
	if err != nil {
		return nil, err
	}
	data, err := cast.ToStringSliceE(res)
	if err != nil {
		return nil, err
	}
	var servers []*base.ServerInfo
	for _, s := range data {
		var info base.ServerInfo
		err := json.Unmarshal([]byte(s), &info)
		if err != nil {
			continue // skip bad data
		}
		servers = append(servers, &info)
	}
	return servers, 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
}

// KEYS[1] -> asynq:paused
// ARGV[1] -> asynq:queues:<qname> - queue to pause
var pauseCmd = redis.NewScript(`
local ismem = redis.call("SISMEMBER", KEYS[1], ARGV[1])
if ismem == 1 then
	return redis.error_reply("queue is already paused")
end
return redis.call("SADD", KEYS[1], ARGV[1])`)

// Pause pauses processing of tasks from the given queue.
func (r *RDB) Pause(qname string) error {
	qkey := base.QueueKey(qname)
	return pauseCmd.Run(r.client, []string{base.PausedQueues}, qkey).Err()
}

// KEYS[1] -> asynq:paused
// ARGV[1] -> asynq:queues:<qname> - queue to unpause
var unpauseCmd = redis.NewScript(`
local ismem = redis.call("SISMEMBER", KEYS[1], ARGV[1])
if ismem == 0 then
	return redis.error_reply("queue is not paused")
end
return redis.call("SREM", KEYS[1], ARGV[1])`)

// Unpause resumes processing of tasks from the given queue.
func (r *RDB) Unpause(qname string) error {
	qkey := base.QueueKey(qname)
	return unpauseCmd.Run(r.client, []string{base.PausedQueues}, qkey).Err()
}