How to use redis to implement delay queue in Golang.

How to use Redis to implement delay queue in Golang

Delay queue is a very practical message processing method. It delays the message for a period of time before processing. It is generally used to implement tasks such as task scheduling and scheduled tasks. . In actual development, Redis is a very commonly used cache database. It provides functions similar to message queues, so we can use Redis to implement delay queues. This article will introduce how to implement a delay queue using Golang and Redis.

1. ZSET of Redis

Redis provides the data structure of sorted sets (ordered sets), which we can use to implement a delay queue. In sorted sets, each element has a score attribute, which is used to indicate the weight of the element. Sorted sets store elements in ascending order of score. Elements with the same score will be sorted according to their members. We can encapsulate each task into an element and use the time it takes to execute the task as the score of the element.

2. Implementation of delay queue

Specifically, we can use Redis’s ZADD command to add tasks to the delay queue. For example:

//添加任务到延迟队列
func AddTaskToDelayQueue(taskId string, delayTime int64) error {
    _, err := redisClient.ZAdd("DelayedQueue", redis.Z{
        Score:  float64(time.Now().Unix() + delayTime),
        Member: taskId,
    }).Result()
    if err != nil {
        return err
    }
    return nil
}

In the above code, we use Redis's ZADD command to add a task to the sorted set named "DelayedQueue". Among them, delayTime indicates the time the task needs to be postponed, and Score is the current time plus the delay time, that is, the timestamp when the task needs to be executed.

In actual business scenarios, we can obtain the element with the smallest score in the delay queue before task execution, that is, the most recent task that needs to be executed:

//获取延迟任务队列中最近需要执行的任务id
func GetNextTaskFromDelayQueue() (string, error) {
    now := time.Now().Unix()
    items, err := redisClient.ZRangeByScore("DelayedQueue", redis.ZRangeBy{
        Min:    "-inf",
        Max:    strconv.FormatInt(now, 10),
        Offset: 0,
        Count:  1,
    }).Result()
    if err != nil {
        return "", err
    }
    if len(items) == 0 {
        return "", nil
    }
    return items[0], nil
}

In the above code, we use Redis's ZRangeByScore command obtains the elements in the delay queue whose score is less than or equal to the current timestamp, and then takes the first element in the list as the next task to be executed.

3. Processing after task execution

After we obtain the tasks that need to be executed from the delay queue, we can move the tasks from the to-be-executed list to the executed list , so that we can count the execution of tasks.

//将已经执行的任务移除
func RemoveTaskFromDelayQueue(taskId string) error {
    _, err := redisClient.ZRem("DelayedQueue", taskId).Result()
    if err != nil {
        return err
    }
    return nil
}

4. Complete code example

We integrated the above code together and added some error handling and log information to get a complete code example:

package delayqueue

import (
    "strconv"
    "time"

    "github.com/go-redis/redis"
)

var redisClient *redis.Client

//初始化redis连接
func InitRedis(redisAddr string, redisPassword string) error {
    redisClient = redis.NewClient(&redis.Options{
        Addr:     redisAddr,
        Password: redisPassword,
        DB:       0,
    })

    _, err := redisClient.Ping().Result()
    if err != nil {
        return err
    }
    return nil
}

//添加任务到延迟队列
func AddTaskToDelayQueue(taskId string, delayTime int64) error {
    _, err := redisClient.ZAdd("DelayedQueue", redis.Z{
        Score:  float64(time.Now().Unix() + delayTime),
        Member: taskId,
    }).Result()
    if err != nil {
        return err
    }
    return nil
}

//获取延迟任务队列中最近需要执行的任务id
func GetNextTaskFromDelayQueue() (string, error) {
    now := time.Now().Unix()
    items, err := redisClient.ZRangeByScore("DelayedQueue", redis.ZRangeBy{
        Min:    "-inf",
        Max:    strconv.FormatInt(now, 10),
        Offset: 0,
        Count:  1,
    }).Result()
    if err != nil {
        return "", err
    }
    if len(items) == 0 {
        return "", nil
    }
    return items[0], nil
}

//将已经执行的任务移除
func RemoveTaskFromDelayQueue(taskId string) error {
    _, err := redisClient.ZRem("DelayedQueue", taskId).Result()
    if err != nil {
        return err
    }
    return nil
}

5. Summary

This article introduces how to use Golang and Redis to implement a delay queue. By using the ZSET data structure, we can easily implement a delay queue, which is very practical in actual development. In addition to delay queues, Redis also provides many other data structures and functions, which are worth exploring and using.

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