Quarkus Scheduler: Thread per method?

[justinjohnson02]

Using quarkus-scheduler I have 4 methods annotated with @Scheduled like the one below.

My question is, how many threads are being used or are allocated for all 4 scheduled methods?

@Scheduled(delay = 1, every = "1m", concurrentExecution = SKIP)
void everyMinute() {
     processBlockingJob();
}

[quarkus-bot[bot]]

/cc @mkouba (scheduler)

[justinjohnson02]

This is using Quarkus 2.16.6 Final btw

[mkouba]

My question is, how many threads are being used or are allocated for all 4 scheduled methods?

It depends. A thread is never reserved or allocated for a scheduled method. Instead, the default executor for blocking tasks is used. In general, the core thread pool is used, but there are some differences between the production and test/dev modes. Note that non-blocking scheduled methods are executed on the Vert.x event loop.

[hatahet]

Is it possible to inject a custom ExecutorService, so that for example we can leverage virtual threads?

[mkouba]

Well, you could do anything inside the scheduled method but the question is whether it would be reasonable ;-).

Speaking about the virtual threads - I'm not sure if @RunOnVirtualThread is currently supported for scheduled methods but I don't think it is. CC @cescoffier

[cescoffier]

It's not supported in @scheduled method. It's a good idea. Can you open an issue? It's rather simple to implement.

[cescoffier]

Note that it will use one virtual thread per method and so may run concurrently (in any order without any guarantee).