Is Spring's built in Scheduler persistent.?

Question

I have run into a case where I have to use a persistent Scheduler, since I have a web application that can crash or close due to some problems and might los

Answer 1

@Schedule has nothing to do with the actual executor. The default java executors aren't persistent (maybe there are some app-server specific ones that are), if you want persistence you have to use Quartz for job execution.

Answer 2

1. No, Spring's @Schedule-annotation will typically only instruct Spring at what times a certain task should be scheduled to run within the current VM. As far as I know there is not a context for the execution either. The schedule is static.

2. I had a similar requirement and created db-scheduler (https://github.com/kagkarlsson/db-scheduler), a simple, persistent and cluster-friendly scheduler. It stores the next execution-time in the database, and triggers execution once it is reached.

A very simple example for a RecurringTask without context could look like this:

final RecurringTask myDailyTask = ComposableTask.recurringTask("my-daily-task", Schedules.daily(LocalTime.of(8, 0)),
                () -> System.out.println("Executed!"));

final Scheduler scheduler = Scheduler
        .create(dataSource)
        .startTasks(myDailyTask)
        .threads(5)
        .build();

scheduler.start();

It will execute the task named my-daily-task at 08:00 every day. It will be scheduled in the database when the scheduler is first started, unless it already exists in the database.

If you want to schedule an ad-hoc task some time in the future with context, you can use the OneTimeTask:

    final OneTimeTask oneTimeTask = ComposableTask.onetimeTask("my-onetime-task",
            (taskInstance, context) -> System.out.println("One-time task with identifier "+taskInstance.getId()+" executed!"));

    scheduler.scheduleForExecution(LocalDateTime.now().plusDays(1), oneTimeTask.instance("1001"));

3. See the example above. Any number of tasks can be scheduled, as long as task-name and instanceIdentifier is unique.