How to implement golang cron

Golang is a language suitable for writing high-concurrency and high-performance applications. Cron is a very practical task scheduler that can automatically execute specified tasks at a specific time or within a certain period.

In daily development, we often need to write scheduled tasks to execute some specific business logic, such as backing up databases, generating reports, updating caches, etc. Golang also provides a corresponding Cron library, which can easily implement the writing of scheduled tasks.

In this article, we will introduce how to use the Cron library to implement the scheduled task function in Golang, and provide some practical application cases.

First, we need to install the Cron library, which can be installed using the following command on the command line:

go get github.com/robfig/cron/v3

Next, we can use the following code to implement a simple scheduled task:

package main

import (
    "fmt"
    "time"

    "github.com/robfig/cron/v3"
)

func main() {
    c := cron.New()
    c.AddFunc("*/5 * * * * *", func() {
        fmt.Println("Every 5 seconds")
    })
    c.Start()

    time.Sleep(20 * time.Second)
    c.Stop()
}

In the above code, we create a new Cron instance and add a scheduled task that executes every 5 seconds. When executing the AddFunc method, we need to pass in two parameters. The first parameter is a string, which represents the Cron expression, that is, the execution time and frequency of the scheduled task; the second parameter is a function, which represents the task to be executed. Task.

You can use Cron expressions to specify the execution time and frequency of scheduled tasks. The Cron expression consists of 6 fields, representing seconds, minutes, hours, days, months, and days of the week (0~6 represents Sunday to Saturday). For example, "0 0 /1 " means that the task is executed every hour.

In the above code, we also added a time.Sleep method to let the program stop all scheduled tasks after 20 seconds of execution.

In addition to AddFunc, we can also use the AddJob method to add scheduled tasks. The AddJob method can use custom Job types to achieve more flexible task scheduling.

package main

import (
    "fmt"
    "time"

    "github.com/robfig/cron/v3"
)

type MyJob struct {}

func (j MyJob) Run() {
    fmt.Println("MyJob is running")
}

func main() {
    c := cron.New()
    c.AddJob("*/5 * * * * *", MyJob{})
    c.Start()

    time.Sleep(20 * time.Second)
    c.Stop()
}

In the above code, we created a MyJob type and implemented the Run method. The MyJob type can be passed to the AddJob method as a parameter to implement scheduling of scheduled tasks.

In addition to the above examples, we can also use the Cron library to implement more complex scheduled tasks. For example, you can write a script to back up a MongoDB database and use the Cron library to perform the backup every day at 3 am. The following is an actual code example:

package main

import (
    "log"
    "os/exec"
    "time"

    "github.com/robfig/cron/v3"
)

func main() {
    c := cron.New()
    c.AddFunc("0 0 3 * * *", func() {
        cmd := exec.Command("mongodump", "--db", "mydb", "--out", "/data/db/backup")
        err := cmd.Start()
        if err != nil {
            log.Fatal(err)
        }

        err = cmd.Wait()
        if err != nil {
            log.Fatal(err)
        }
    })
    c.Start()

    time.Sleep(24 * time.Hour)
    c.Stop()
}

In the above code, we use the AddFunc method to implement a scheduled backup task at 3 am every day. The backup command is implemented by using the exec package to call the external mongodump command. The specific backup path and database name can be modified according to the actual situation.

In this article, we introduce how to use the Cron library to implement scheduled tasks in Golang. Through this simple library, we can easily write scheduled tasks and implement some practical application scenarios. At the same time, we can also write complex scheduled tasks according to actual needs and implement more powerful functions.

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