Make it possible to configure any TaskExecutor through ChannelRegistration

[uumarov]

Affect: Spring Boot 3.2.2, spring-messaging-6.1.3

Make it possible to set SimpleAsyncTaskExecutor for a channel through ChannelRegistration.taskExecutor(taskExecutor), not only ThreadPoolTaskExecutor, to support Java 21 virtual threads. And it might be worth making the default use of SimpleAsyncTaskExecutor as channel's TaskExecutor when spring.threads.virtual.enabled=true in Spring Boot 3.2

spring-framework/spring-messaging/src/main/java/org/springframework/messaging/simp/config/ChannelRegistration.java

Line 54 in 6bd7f02

public TaskExecutorRegistration taskExecutor(@Nullable ThreadPoolTaskExecutor taskExecutor) {

[snicoll]

Thanks for the suggestion.

Things have changed quite a bit since ChannelRegistration was designed. It's backed by TaskExecutorRegistration that is thread pool based since the registration can customize a number of things such as pool size and what not. Looking at the code, the customization seems to be used when creating an instance behind the scenes for you was an option.

@rstoyanchev I wonder if we couldn't simplify all that and allow the registration of an already-defined task executor so that SimpleAsyncTaskExecutor can be provided by Spring Boot when virtual threads are enabled.

[rstoyanchev]

@snicoll, it seems I overlooked this in the changes for 6.1 to enable virtual threads. We need to provide a way to pass an externally prepared TaskExecutor through an additional method on ChannelRegistration.

[jhoeller]

Avoiding another overloaded taskExecutor method (which would be ambiguous for taskExecutor(null) calls then), we could introduce a void executor(Executor) method. We don't need to declare our TaskExecutor interface there in any case, we accept java.util.concurrent.Executor (which TaskExecutor extends) in many other places as well.