Why is the @Async task in Spring Boot scheduler not running every 1 second

Question

I am not able to understand the behavior of method defined with @Async annotation. As per my understanding the method should be executed every 1 second. But I see otherwise.

@EnableAsync
@Component
public class AsyncSchedulingDemo {

    private static final SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");

    //every 1 second, INSTANT start of job but waits for the first job to finish hence takes 10 seconds
    //here the next execution will start after 10 seconds because the job takes 10 seconds to finish
    @Scheduled(fixedRate = 1000)
    public void performFixedRateTask_W_LongRunningJob() throws InterruptedException {
        System.out.println("Task performed every 1 second but waits for the first one to finish before the next execution starts " + dateFormat.format(new Date()));
        Thread.sleep(10000);
    }

    //should be executed every 1 second because of @Async
    //here the next execution should start IMMEDIATELY and does NOT wait for the first one to finish
    @Async
    @Scheduled(fixedRate = 1000)
    public void performFixedRateTask_With_Async() throws InterruptedException {
        System.out.println("Async Task performed every 1 second as it does NOT wait for the first one to finish " + dateFormat.format(new Date()));
        Thread.sleep(10000);
    }

}

Console Log:

Task performed every 1 second but waits for the first one to finish before the next execution starts 05/13/2020 15:54:51
Async Task performed every 1 second as it does NOT wait for the first one to finish 05/13/2020 15:54:51

Task performed every 1 second but waits for the first one to finish before the next execution starts 05/13/2020 15:55:01
Async Task performed every 1 second as it does NOT wait for the first one to finish 05/13/2020 15:55:01

Task performed every 1 second but waits for the first one to finish before the next execution starts 05/13/2020 15:55:11
Async Task performed every 1 second as it does NOT wait for the first one to finish 05/13/2020 15:55:11

===UPDATED===

If I comment out the very first method completely and execute the application again I see that the second method executes every second. Why ?? How is the first method preventing the execution of second one ?

Console Log:

Async Task performed every 1 second as it does NOT wait for the first one to finish 05/13/2020 16:45:48
Async Task performed every 1 second as it does NOT wait for the first one to finish 05/13/2020 16:45:49
Async Task performed every 1 second as it does NOT wait for the first one to finish 05/13/2020 16:45:50
Async Task performed every 1 second as it does NOT wait for the first one to finish 05/13/2020 16:45:51

This has nothing to do with `@Async`. This is behavior of `@Scheduled` that depends on your scheduling configuration. Please provide a [mcve]. — Sotirios Delimanolis, May 13 '20 at 20:08
Some related question https://stackoverflow.com/questions/42482865/using-scheduled-and-async-together — Michael Kreutz, May 13 '20 at 20:12
https://stackoverflow.com/questions/14623092/using-spring-scheduled-and-async-together — Sotirios Delimanolis, May 13 '20 at 20:13

Kristof · Answer 1 · 2020-05-13T21:24:14.700

1

I think, it is because the default pool-size for threads used for executing @Scheduled annotated methods is 1 according to spring documentation: "If you do not provide a 'pool-size' attribute, the default thread pool will only have a single thread."

As the first method is not @Async, it is blocking the only thread.

edited May 13 '20 at 21:24

answered May 13 '20 at 21:18

Kristof

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2
7

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I will create a threadpool and check that theory. Thanks for the pointer. – Nital May 16 '20 at 18:54

Why is the @Async task in Spring Boot scheduler not running every 1 second

1 Answers1