Support kotlin coroutines in quarkus-scheduler

[mschorsch]

Description

quarkus-scheduler does not support suspend functions.

In the past i bridged the gap with custom code, but i think it should be supported by quarkus.

I had this requirement multiple times.

@ApplicationScoped
class SomeBean {

    @Scheduled(every="10s")     
    suspend fun doSomething() {
        // ...
    }
}

Implementation ideas

No response

[quarkus-bot]

/cc @evanchooly, @mkouba

[mschorsch]

@geoand 😃

[geoand]

Interesting idea!

[mkouba]

Hm, what's the point of turning a scheduled method into a coroutine? I mean it's not called directly from a user code and it's always executed on the main executor for blocking tasks. But I'm probably missing something here...

[geoand]

I assume so users can use coroutine enabled APIs

[mschorsch]

I assume so users can use coroutine enabled APIs

That's the point.

With this change other suspend functions can be called directly.

[mkouba]

Ok, contributions are welcome. I have no idea what needs to be implemented ;-).

[geoand]

I can take a look sometime after I get back, but it won't be high priority

[evanchooly]

I'm not convinced the complexity is worth it. It's trivially simple to launch subsequent suspend functions via runBlocking or launch. Given the asynchronous out-of band execution of the functions it feels like time could be better spent on more user facing concerns.

[evanchooly]

Has anything come of this? what's the problem with using runBlocking {} inside your scheduled task?

[mschorsch]

runBlocking blocks the underlying thread.

If i make for example an API call inside a scheduled method, the underlying thread is blocked as long as the API call takes.

[evanchooly]

launch {} doesn't however

[mschorsch]

Do you mean GlobalScope.launch? This isn't a good option because of:

It is easy to accidentally create resource or memory leaks when GlobalScope is used. A coroutine launched in GlobalScope is not subject to the principle of structured concurrency, so if it hangs or gets delayed due to a problem (e.g. due to a slow network), it will stay working and consuming resources.

https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-global-scope/

I've written some glue code using a custom coroutine scope but i think it would be best if Quarkus would manage the ApplicationCoroutineScope in the same manner as in resteasy reactive.

[geoand]

This can definitely be done the proper way (like we have done in RESTEasy Reactive), but it's pretty low on our priority list...

[mschorsch]

@geoand @mkouba Thanks

[geoand]

🎉

[andreas-eberle]

@geoand : When will this be released? Could it make it to 2.8.1?

[geoand]

It will be part of Quarkus 2.9

[andreas-eberle]

Is there a planned release date for 2.9 already? 2.8 just came out and we cannot upgrade since 2.7.3 since we get into trouble with Hibernate Reactive...

[geoand]

CR1 should be end of April if all goes well

[JamshedAlamQaderi]

Can anyone tell me how to use @Scheduled with kotlin coroutine?

[geoand]

Just annotate a public suspend function with @Suspend

[JamshedAlamQaderi]

@geoand thanks for your help. Can you provide me the actual package for @Suspend

[geoand]

Sorry, I meant @Scheduled

[JamshedAlamQaderi]

I am using io.quarkus:quarkus-scheduler. Is that okay for coroutine?

[geoand]

Yes