用 Redis 做一个可靠的延迟队列

package main
import (
 "github.com/go-redis/redis/v8"
 "github.com/hdt3213/delayqueue"
 "strconv"
 "time"
)
func main() {
 redisCli := redis.NewClient(&redis.Options{
  Addr: "127.0.0.1:6379",
 })
 queue := delayqueue.NewQueue("example-queue", redisCli, func(payload string) bool {
  // 注册处理消息的回调函数
        // 返回 true 表示已成功消费，返回 false 消息队列会重新投递次消息
  return true
 })
 // 发送延时消息
 for i := 0; i < 10; i++ {
  err := queue.SendDelayMsg(strconv.Itoa(i), time.Hour, delayqueue.WithRetryCount(3))
  if err != nil {
   panic(err)
  }
 }
 // 启动消费协程
 done := queue.StartConsume()
 // 阻塞等待消费协程退出
 <-done
}

-- keys: pendingKey, readyKey
-- argv: currentTime
local msgs = redis.call('ZRangeByScore', KEYS[1], '0', ARGV[1])  -- 从 pending key 中找出已到投递时间的消息
if (#msgs == 0) then return end
local args2 = {'LPush', KEYS[2]} -- 将他们放入 ready key 中
for _,v in ipairs(msgs) do
 table.insert(args2, v) 
end
redis.call(unpack(args2))
redis.call('ZRemRangeByScore', KEYS[1], '0', ARGV[1])  -- 从 pending key 中删除已投递的消息

-- keys: readyKey/retryKey, unackKey
-- argv: retryTime
local msg = redis.call('RPop', KEYS[1])
if (not msg) then return end
redis.call('ZAdd', KEYS[2], ARGV[1], msg)
return msg

-- keys: unackKey, retryCountKey, retryKey, garbageKey
-- argv: currentTime
local msgs = redis.call('ZRangeByScore', KEYS[1], '0', ARGV[1])  -- 找到已到重试时间的消息
if (#msgs == 0) then return end
local retryCounts = redis.call('HMGet', KEYS[2], unpack(msgs)) -- 查询剩余重试次数
for i,v in ipairs(retryCounts) do
 local k = msgs[i]
 if tonumber(v) > 0 then -- 剩余次数大于 0
  redis.call("HIncrBy", KEYS[2], k, -1) -- 减少剩余重试次数
  redis.call("LPush", KEYS[3], k) -- 添加到 retry key 中
 else -- 剩余重试次数为 0
  redis.call("HDel", KEYS[2], k) -- 删除重试次数记录
  redis.call("SAdd", KEYS[4], k) -- 添加到垃圾桶，等待后续删除
 end
end
redis.call('ZRemRangeByScore', KEYS[1], '0', ARGV[1])  -- 将已处理的消息从 unack key 中删除

func (q *DelayQueue) garbageCollect() error {
 ctx := context.Background()
 msgIds, err := q.redisCli.SMembers(ctx, q.garbageKey).Result()
 if err != nil {
  return fmt.Errorf("smembers failed: %v", err)
 }
 if len(msgIds) == 0 {
  return nil
 }
 // allow concurrent clean
 msgKeys := make([]string, 0, len(msgIds))
 for _, idStr := range msgIds {
  msgKeys = append(msgKeys, q.genMsgKey(idStr))
 }
 err = q.redisCli.Del(ctx, msgKeys...).Err()
 if err != nil && err != redis.Nil {
  return fmt.Errorf("del msgs failed: %v", err)
 }
 err = q.redisCli.SRem(ctx, q.garbageKey, msgIds).Err()
 if err != nil && err != redis.Nil {
  return fmt.Errorf("remove from garbage key failed: %v", err)
 }
 return nil
}

func (q *DelayQueue) ack(idStr string) error {
 ctx := context.Background()
 err := q.redisCli.ZRem(ctx, q.unAckKey, idStr).Err()
 if err != nil {
  return fmt.Errorf("remove from unack failed: %v", err)
 }
 // msg key has ttl, ignore result of delete
 _ = q.redisCli.Del(ctx, q.genMsgKey(idStr)).Err()
 q.redisCli.HDel(ctx, q.retryCountKey, idStr)
 return nil
}

func (q *DelayQueue) nack(idStr string) error {
 ctx := context.Background()
 // update retry time as now, unack2Retry will move it to retry immediately
 err := q.redisCli.ZAdd(ctx, q.unAckKey, &redis.Z{
  Member: idStr,
  Score:  float64(time.Now().Unix()),
 }).Err()
 if err != nil {
  return fmt.Errorf("negative ack failed: %v", err)
 }
 return nil
}

func (q *DelayQueue) consume() error {
 // 执行 pending2ready，将已到时间的消息转移到 ready
 err := q.pending2Ready()
 if err != nil {
  return err
 }
 // 循环调用 ready2Unack 拉取消息进行消费
 var fetchCount uint
 for {
  idStr, err := q.ready2Unack()
  if err == redis.Nil { // consumed all
   break
  }
  if err != nil {
   return err
  }
  fetchCount++
  ack, err := q.callback(idStr)
  if err != nil {
   return err
  }
  if ack {
   err = q.ack(idStr)
  } else {
   err = q.nack(idStr)
  }
  if err != nil {
   return err
  }
  if fetchCount >= q.fetchLimit {
   break
  }
 }
 // 将 nack 或超时的消息放入重试队列
 err = q.unack2Retry()
 if err != nil {
  return err
 }
    // 清理已达到最大重试次数的消息
 err = q.garbageCollect()
 if err != nil {
  return err
 }
 // 消费重试队列
 fetchCount = 0
 for {
  idStr, err := q.retry2Unack()
  if err == redis.Nil { // consumed all
   break
  }
  if err != nil {
   return err
  }
  fetchCount++
  ack, err := q.callback(idStr)
  if err != nil {
   return err
  }
  if ack {
   err = q.ack(idStr)
  } else {
   err = q.nack(idStr)
  }
  if err != nil {
   return err
  }
  if fetchCount >= q.fetchLimit {
   break
  }
 }
 return nil
}