[FEATURE] - OneTime jobs should have the option to be deleted on completion

[rigens]

Describe the bug

...

To Reproduce

func main() {
	scheduler, err := gocron.NewScheduler(gocron.WithLocation(time.UTC))
	if err != nil {
		log.Fatal(err)
	}

	total := 100

	var wg sync.WaitGroup
	wg.Add(total)

	for i := 0; i < total; i++ {
		runAt := time.Now().UTC().Add(5 * time.Second)
		_, err := scheduler.NewJob(
			gocron.OneTimeJob(gocron.OneTimeJobStartDateTime(runAt)),
			gocron.NewTask(func() {
				log.Printf("running job at %s", time.Now().UTC())
				wg.Done()
			}),
		)
		if err != nil {
			log.Fatal(err)
		}
	}

	scheduler.Start()
	wg.Wait()

	log.Printf("total jobs: %d", len(scheduler.Jobs()))
}

Version

v2.2.9

Expected behavior

scheduler.Jobs() should return an empty slice after completing all OneTime jobs

Additional context

[JohnRoesler]

I don't consider this a bug. Currently, you can run a one time job, and then if you choose to, can run it manually using RunNow().

I think this could be changed to a feature request to optionally remove the job when done.

[rigens]

Currently, you can run a one time job, and then if you choose to, can run it manually using RunNow()

Why would I use RunNow() if I can call the corresponding function directly

I don't consider this a bug.

This is a bug, OneTime jobs should be removed from the scheduler after execution (see quartz or apscheduler for example)

[Zhwt]

For anyone who comes later: you may want to use gocron.WithLimitedRuns(1) to make the job deleting itself upon completion. Example for the code above:

_, err := scheduler.NewJob(
	gocron.OneTimeJob(gocron.OneTimeJobStartDateTime(runAt)),
	gocron.NewTask(func() {
		log.Printf("running job at %s", time.Now().UTC())
		wg.Done()
	}),
	gocron.WithLimitedRuns(1),
)

But please note that there seems to be some subtle difference between the job being fired by the scheduler and directly called using job.RunNow(). The job seems to be counted as "done and removed" in fired job, and will be counted as "not started yet" or "done and removed" state when calling RunNow(). Reproduce code:

package main

import (
	"fmt"
	"github.com/go-co-op/gocron/v2"
	"time"
)

var s gocron.Scheduler

func remainingJobCount() {
	// remove this delay to see the difference
	time.Sleep(time.Microsecond * 10)
	fmt.Println("there are", len(s.Jobs()), "jobs in the queue")
}

func main() {
	var err error
	s, err = gocron.NewScheduler()
	if err != nil {
		fmt.Println(err)
	}
	s.Start()

	j, err := s.NewJob(
		gocron.OneTimeJob(gocron.OneTimeJobStartDateTime(time.Now().Add(time.Second))),
		gocron.NewTask(remainingJobCount),
		gocron.WithLimitedRuns(2),
	)
	if err != nil {
		fmt.Println(err)
	}

	time.Sleep(time.Second * 2)

	err = j.RunNow()
	if err != nil {
		fmt.Println(err)
	}

	time.Sleep(time.Second)

	remainingJobCount()
}

Will result in:

there are 1 jobs in the queue
there are 1 jobs in the queue
there are 0 jobs in the queue

or

there are 1 jobs in the queue
there are 0 jobs in the queue
there are 0 jobs in the queue

But the first one will always be 1. I'm not sure if this is the desired behavior, so I'm not posting this as a issue.