💚 CLA has been signed

Hello @fabriziofortino, thank you for the contribution and for highlighting this issue. I have tested your solution and while it helps mitigate the problem, when dealing with many requests there's still a possibility that the latest listener tasks are ignored because of the shutdown. I'll do more testing to figure out a way to handle this reliably, I'll let you know so that we can fix this PR and merge it.

@fabriziofortino do you mind if I push on this branch?

@l-trotta no problem, go ahead!

@l-trotta I have also noticed this: in the close() method when the scheduler is internal shutdownNow() gets called:

       if (scheduler != null && !isExternalScheduler) {
            scheduler.shutdownNow();
        }

This will try to cancel the already submitted tasks. Shouldn't we call shutdown() instead?

@fabriziofortino you're correct, however with the new changes it shouldn't be a problem either way, you can take a look :)

This fix does not seem to be included in the 8.16.0 release. It looks like the 8.16 branch was cut on Sep 10, while this pull request was merged into 8.15 on Sep 12 and then never ported to 8.16. Can you please take a look? This affects our bulk indexing.

@blackwinter you're correct, I backported it to 8.x where 8.16 was branched from, but forgot 8.16 itself. Sorry for the inconvenience, I'll port it right away, I'll let you know if we made it in time for it to be in 8.16.1

@blackwinter no luck, didn't make it in time for the release. You can either wait for 8.16.2, which should be out next month, or you can use 8.16.1-SNAPSHOT from our snapshot repo, for example in gradle:

repositories {
    mavenCentral()
    maven {
        url = uri("https://snapshots.elastic.co/maven/")
    }
    ...
}
...
dependencies {
    ...
    implementation("co.elastic.clients:elasticsearch-java:8.16.1-SNAPSHOT")
    ...
}

Too bad. But thanks anyway. The snapshot seems to work (it's also available from Sonatype).