Simple task scheduling with Redis & Go. Similar to Sidekiq's `perform_in` and `perform_at`.

poller.go

// poller.go

package main

import (
	"fmt"
	"os"
	"os/signal"
	"time"

	"github.com/fzzy/radix/redis"
)

var redisConn *redis.Client

func init() {
	var err error
	if redisConn, err = redis.Dial("tcp", "127.0.0.1:6379"); err != nil {
		panic(err)
	}
}

// Poll checks Redis to determine whether scheduled tasks need to be run or not.
func Poll(interval time.Duration, done <-chan os.Signal) {
	ticker := time.NewTicker(interval)
	for {
		select {
		case <-ticker.C:
			fmt.Print("> Checking for scheduled tasks... ")
			nowUnix := time.Now().Unix()
			response := redisConn.Cmd("ZRANGEBYSCORE", "jobs:scheduled", "-inf", float64(nowUnix))
			tasks, _ := response.List()

			if len(tasks) == 0 {
				fmt.Println("No tasks found.")
			}

			for _, task := range tasks {
				fmt.Printf("Queue task: %s\n", task)
				redisConn.Cmd("ZREM", "jobs:scheduled", task)
			}
		case <-done:
			fmt.Println("Shutting down poller")
			return
		}
	}
}

func main() {
	c := make(chan os.Signal)
	signal.Notify(c, os.Interrupt)
	fmt.Println("Polling Redis every 15 seconds for scheduled tasks...")
	Poll(15 * time.Second, c)
}

scheduler.go

// scheduler.go

package main

import (
	"fmt"
	"os"
	"os/signal"
	"time"

	"github.com/fzzy/radix/redis"
)

var redisConn *redis.Client

func init() {
	var err error
	if redisConn, err = redis.Dial("tcp", "127.0.0.1:6379"); err != nil {
		panic(err)
	}
}

// PerformIn schedules a given task to be executed in the given duration.
func PerformIn(in time.Duration, task string) {
	at := time.Now().Add(in)
	PerformAt(at, task)
}

// PerformAt schedules a task to be executed at a given time.
func PerformAt(at time.Time, task string) {
	fmt.Printf("> Scheduling %s with score %d\n", task, at.Unix())
	redisConn.Cmd("zadd", "jobs:scheduled", float64(at.Unix()), task)
}

func main() {
	at, _ := time.Parse("2006-Jan-02", "2016-Jan-01")
	PerformAt(at, "Happy New Year!")
	PerformIn(2 * time.Minute, "Snooze wakeup alarm!")
}