Beego

# Task

Tasks work very similarly to cron jobs. Tasks are used to run a job outside the normal request/response cycle. These can be adhoc or scheduled to run regularly. Examples include: Reporting memory and goroutine status, periodically triggering GC or cleaning up log files at fixed intervals.

# Creating a new Task

To initialize a task implement :

tk1 := task.NewTask("tk1", "0 12 * * * *", func(ctx context.Context) error {
	fmt.Println("tk1")
	return nil
})

The NewTask signature:

NewTask(tname string, spec string, f TaskFunc) *Task
  • tname: Task name
  • spec: Task format. See below for details.
  • f: The function which will be run as the task.

To implement this task, add it to the global task list and start it.

task.AddTask("tk1", tk1)
task.StartTask()
defer task.StopTask()

# Testing the TaskFunc

Use the code below to test if the TaskFunc is working correctly.

err := tk.Run()
if err != nil {
	t.Fatal(err)
}

# spec in detail

spec specifies when the new Task will be run. Its format is the same as that of traditional crontab:

// The first 6 parts are:
//       second: 0-59
//       minute: 0-59
//       hour: 1-23
//       day: 1-31
//       month: 1-12
//       weekdays: 0-6（0 is Sunday）

// Some special sign:
//       *: any time
//       ,: separator. E.g.: 2,4 in the third part means run at 2 and 4 o'clock
//　　    －: range. E.g.: 1-5 in the third part means run between 1 and 5 o'clock
//       /n : run once every n time. E.g.: */1 in the third part means run once every an hour. Same as 1-23/1
/////////////////////////////////////////////////////////
//	0/30 * * * * *                        run every 30 seconds
//	0 43 21 * * *                         run at 21:43
//	0 15 05 * * *                         run at 05:15
//	0 0 17 * * *                          run at 17:00
//	0 0 17 * * 1                          run at 17:00 of every Monday
//	0 0,10 17 * * 0,2,3                   run at 17:00 and 17:10 of every Sunday, Tuesday and Wednesday
//	0 0-10 17 1 * *                       run once every minute from 17:00 to 7:10 on 1st day of every month
//	0 0 0 1,15 * 1                        run at 0:00 on 1st and 15th of each month and every Monday
//	0 42 4 1 * *                          run at 4:42 on 1st of every month
//	0 0 21 * * 1-6                        run at 21:00 from Monday to Saturday
//	0 0,10,20,30,40,50 * * * *            run every 10 minutes
//	0 */10 * * * *                        run every 10 minutes
//	0 * 1 * * *                           run every one minute from 1:00 to 1:59
//	0 0 1 * * *                           run at 1:00
//	0 0 */1 * * *                         run at :00 of every hour
//	0 0 * * * *                           run at :00 of every hour
//	0 2 8-20/3 * * *                      run at 8:02, 11:02, 14:02, 17:02 and 20:02
//	0 30 5 1,15 * *                       run at 5:30 of 1st and 15th of every month

# Debug module (Already moved to utils module)

We always use print for debugging. But the default output is not good enough for debugging. Beego provides this debug module:

  • Display() - print result to console.
  • GetDisplayString() - return the string.

It print key/value pairs. The following code:

Display("v1", 1, "v2", 2, "v3", 3)

will output:

2013/12/16 23:48:41 [Debug] at TestPrint() [/Users/astaxie/github/beego/task/debug_test.go:13]

[Variables]
v1 = 1
v2 = 2
v3 = 3

For pointer type:

type mytype struct {
	next *mytype
	prev *mytype
}	

var v1 = new(mytype)
var v2 = new(mytype)

v1.prev = nil
v1.next = v2

v2.prev = v1
v2.next = nil

Display("v1", v1, "v2", v2)

The output result:

2013/12/16 23:48:41 [Debug] at TestPrintPoint() [/Users/astaxie/github/beego/task/debug_test.go:26]

[Variables]
v1 = &task.mytype{
    next: &task.mytype{
        next: nil,
        prev: 0x210335420,
    },
    prev: nil,
}
v2 = &task.mytype{
    next: nil,
    prev: &task.mytype{
        next: 0x210335430,
        prev: nil,
    },
}

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