Running each Spring Scheduler in its own thread

Question

I have multiple components with @Scheduled annotations, and I see that Spring only starts one at a time, even if they are scheduled to run on the same time.

My use case is as follows. I want each @Scheduled annotation to run in its own thread, but only once for each thread.

Given this pseudo code with two schedulers:

@Scheduled(cron = "0 * * * * *") //run every minute
public void methodA() {
   log.info("Running method A");
   executeLongRunningJob("Finished method A");
}

@Scheduled(cron = "0 * * * * *") //run every minute
public void methodB() {
   log.info("Running method B");
   executeLongRunningJob("Finished method B");       
}

private void executeLongRunningJob(String msg) {
    Thread.sleep(70 seconds);
    System.out.println(msg);
}

Note that the task takes longer time than the scheduler is scheduled to run. This is crucial. I don't want the scheduler to start again before its finished running.

Running this code out of the box gives me this output:

Running method A
Finished method A
Running method B
Finished method B
Running method A
Finished method A
Running method B
Finished method B
... and so on

So obviously its running both schedulers in a single thread.

When I put @Async on my expensive method, then I almost get the correct behavior, except the expensive method is not finished before a new scheduler is started.

Running method A
Running method B
Running method A
Running method B
Finished method A
Finished method B
... and so on

What I would like is this output:

Running method A  
Running method B
Finished method A 
Finished method B 
Running method A 
Running method B 
Finished method A 
Finished method B
... and so on

How can I accomplish this? I want each Scheduler to run concurrently, but wait until it is finished before allowed to run again. Remember I have more than two Schedulers running in same and sometimes different times.

Running each Spring Scheduler in its own thread

1 Answers