Revise an ExecutorService injections in favor of injected TaskExecutor

[artembilan]

Samples are PostgresChannelMessageTableSubscriber, org.springframework.integration.hazelcast.leader.LeaderInitiator.
These threads potentially can be created as virtual threads with Java 21.

[garyrussell]

Consider using a TaskExecutor instead of a TF directly.

I tested virtual threads with spring-kafka with this...

	@Bean
	ApplicationRunner runner(KafkaTemplate<String, String> template,
			ConcurrentKafkaListenerContainerFactory<?, ?> factory) {

		ThreadFactory tFactory = Thread.ofVirtual().factory();
		factory.getContainerProperties().setListenerTaskExecutor(new SimpleAsyncTaskExecutor(tFactory));
		return args -> {
			template.send("loom1", "test");
			template.send("loom1", "test");
			template.send("loom1", "test");
			template.send("loom1", "test");
			Thread.sleep(5000);
		};
	}

[artembilan]

What I don't like with a single managed TaskExecutor that threads in different components are going to have same prefix in their names.
It is a bit inconvenient when you trace the logic in the logs.
With the name of a thread dedicated to the specific component it is very clear what is going on.

Probably the whole paradigm of managed executor doesn't bring any value when we switch to virtual threads.
It might really be convenient from microservice perspective when Spring Boot gives us this or that TaskExecutor automatically, but for more complex and asynchronous applications like with Spring Integration, it is really misleading to use same prefix name for all virtual threads.

We can continue discussion though since I don't claim to be expert in this area: just sharing my pain over years with single managed executor.

Out of context, but still might be an argument for TaskExecutor injection in some places, @tzolov . See, there is an org.springframework.core.task.support.ExecutorServiceAdapter for our convenience when we would like to deal with Future<?> submit().

[garyrussell]

I didn't mean a single shared TE, each component can get its own.

In any case, as I've said before, unless something has changed, VTs don't get a name for logging purposes; I added this property to the listener container:

spring-projects/spring-kafka#2501

[artembilan]

Yeah...
The point is that we talk about those components which uses only a single thread, like LockRegistryLeaderInitiator.
But yeah, for consistency, a single-threaded TE could be used as well.