Spring @Scheduled annotation random delay

Question

I am using the @Scheduled annotation from Spring framework to invoke a method. But I have multiple nodes in my setup and I do not want them to all run at exactly the same time. So I'd like to set a random value to the initial delay to offset them from each other.

import org.springframework.scheduling.annotation.Scheduled;

@Scheduled(fixedRate = 600000, initialDelay = <random number between 0 and 10 minutes> )

Unfortunately, I am only allowed to use a constant expression here. Is there any other way around this? I thought of using Spring expression language.

Sanguine

Related: Spring @Scheduled to be started every day at a random minute between 4:00AM and 4:30AM – Moiety

Answer 1

You can configure the initialDelay through Spring Expression Language:

@Scheduled(fixedRate = 600000, initialDelayString = "#{ T(java.util.concurrent.ThreadLocalRandom).current().nextInt(10*60*1000) }" )

I don't have an IDE to test that code right now, so you may need to adapt that a bit.

Orphrey

Don't SpEl commands need to be in strings? I've only seen them used in string based values. This unfortunately is expecting a long value. I tried it unquoted and got unresolved compilation problems. I tried it quoted as a string and the scheduler never got invoked but no error messages. – Sanguine

Have you noticed the use of initialDelayString instead of initialDelay? The latter takes a long, the first a string which can be an expression. – Lennox

The example does not quite work. First, it must quoted or the compiler will complain. But even then, all I get is null. Is there som kind of configuration that I need to do? – Kylander

Confirmed with multiple Spring versions that this does not work – Configuration

Answer 2

To make the initial delay randomly somewhere between 0 and the fixedRate try this:

@Scheduled(fixedDelayString = "${some.delay}", initialDelayString = "${random.int(${some.delay})}")

Where you define some.delay (but pick a more suitable name) as 10 minutes as a property like so in your application.properties or equivalent.

some.delay = 600000

Of course if you want to be lazy and hard code it you can always just use ${random.int(600000)}

Carbohydrate

Just wanted to add this alternative answer as the 'correct' answer isn't really helpful and yet this page is high up in search results. – Carbohydrate

Confirmed with multiple Spring versions that this does not work – Configuration

I have used this exact solution in multiple projects, and it worked great. Have not tried it with most recent versions of spring. – Dorking

Answer 3

In this working example, the random delay will be between 5 and 10 seconds.

@Scheduled(fixedDelayString = "#{new Double((T(java.lang.Math).random() + 1) * 5000).intValue()}")

Disinfection

Answer 4

Keep in mind, that the initialDelayString is evaluated only once at startup and then this same values is used whenever the job is scheduled.

See org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor#processScheduled

Elegiac

Do you know a way to have the scheduler not only have a constant random value evaluated at startup, but a random value between each triggering? – Disinfection

Answer 5

This should work

@Scheduled(fixedRate = 600000, initialDelay = "#{new java.util.Random().nextInt(700)}")

Verified it with this simple test:

    @Test
    public void testSpEL() {
       ExpressionParser parser = new SpelExpressionParser();
       Expression exp = parser.parseExpression("new java.util.Random().nextInt(500)");
       Integer value =(Integer) exp.getValue();
       Assertions.assertThat(value).isNotNull();
}

Cloris

Answer 6

In kotlin this works:

@Component
class MyJob {
   companion object {
      const val INTERVAL = 24*3600*1000L // once a day
   }

   @Scheduled(fixedRate = INTERVAL, initialDelayString = "\${random.long($INTERVAL)}")
   fun doDaily() {
      ...
   }
}

Quathlamba

Answer 7

The shortest way I found is:

@Scheduled(initialDelayString = "#{T(Math).round(T(Math).random()*600000)}")

Keele

Answer 8

Or you could just add Thread.sleep(...) at the end of your function.

@Scheduled(fixedDelay = 10000)
public void replicateData() {

    ... do stuff ...

    try {
        Thread.sleep(RandomUtils.nextLong(1000, 10000));
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

Whitewing

It would need to be a random delay at the start of the function. And there would need to be code to make that delay only the first time. That might work but probably a bit clunky – Sanguine