package main

import (
	"fmt"
	"time"
)

/*
基于go實(shí)現(xiàn)延遲隊(duì)列
*/
type Task struct {
	ExecuteTime time.Time
	Job         func()
}

type DelayQueue struct {
	Tasks []*Task
}

func (d *DelayQueue) AddTask(t *Task) {
	d.Tasks = append(d.Tasks, t)
}

func (d *DelayQueue) RemoveTask() {
	//FIFO: remove the first task to enqueue
	d.Tasks = d.Tasks[1:]
}

func (d *DelayQueue) ExecuteTask() {
	for len(d.Tasks) > 0 {
		//dequeue a task
		currentTask := d.Tasks[0]
		if time.Now().Before(currentTask.ExecuteTime) {
			//if the task execution time is not up, wait
			time.Sleep(currentTask.ExecuteTime.Sub(time.Now()))
		}
		//execute the task
		currentTask.Job()
		//remove task who has been executed
		d.RemoveTask()
	}

}

func main() {
	fmt.Println("start delayQueue")
	delayQueue := &DelayQueue{}
	firstTask := &Task{
		ExecuteTime: time.Now().Add(time.Second * 1),
		Job: func() {
			fmt.Println("executed task 1 after delay")
		},
	}
	delayQueue.AddTask(firstTask)
	secondTask := &Task{
		ExecuteTime: time.Now().Add(time.Second * 7),
		Job: func() {
			fmt.Println("executed task 2 after delay")
		},
	}
	delayQueue.AddTask(secondTask)
	delayQueue.ExecuteTask()
	fmt.Println("all tasks have been done!!!")
}

# 安裝docker
yum install -y yum-utils
yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo
yum install docker
systemctl start docker

# docker搭建redis
mkdir -p /Users/ziyi2/docker-home/redis
docker run -d --name redis -v /Users/ziyi2/docker-home/redis:/data -p 6379:6379 redis

package main

import (
	"fmt"
	"github.com/go-redis/redis"
	log "github.com/ziyifast/log"
	"time"
)

/*
基于redis zset實(shí)現(xiàn)延遲隊(duì)列
*/
var redisdb *redis.Client
var DelayQueueKey = "delay-queue"

func initClient() (err error) {
	redisdb = redis.NewClient(&redis.Options{
		Addr:     "localhost:6379",
		Password: "", // not set password
		DB:       0,  //use default db
	})
	_, err = redisdb.Ping().Result()
	if err != nil {
		log.Errorf("%v", err)
		return err
	}
	return nil
}

func main() {
	err := initClient()
	if err != nil {
		log.Errorf("init redis client err: %v", err)
		return
	}
	addTaskToQueue("task1", time.Now().Add(time.Second*3).Unix())
	addTaskToQueue("task2", time.Now().Add(time.Second*8).Unix())
	//執(zhí)行隊(duì)列中的任務(wù)
	getAndExecuteTask()
}

// executeTime為unix時間戳，作為zset中的score。允許redis按照task應(yīng)該執(zhí)行時間來進(jìn)行排序
func addTaskToQueue(task string, executeTime int64) {
	err := redisdb.ZAdd(DelayQueueKey, redis.Z{
		Score:  float64(executeTime),
		Member: task,
	}).Err()
	if err != nil {
		panic(err)
	}
}

// 從redis中取一個task并執(zhí)行
func getAndExecuteTask() {
	for {
		tasks, err := redisdb.ZRangeByScore(DelayQueueKey, redis.ZRangeBy{
			Min:    "-inf",
			Max:    fmt.Sprintf("%d", time.Now().Unix()),
			Offset: 0,
			Count:  1,
		}).Result()
		if err != nil {
			time.Sleep(time.Second * 1)
			continue
		}
		//處理任務(wù)
		for _, task := range tasks {
			fmt.Println("Execute task: ", task)
			//執(zhí)行完任務(wù)之后用 ZREM 移除該任務(wù)
			redisdb.ZRem(DelayQueueKey, task)
		}
		time.Sleep(time.Second * 1)
	}
}