Custom Actuator Endpoint with MediaType as text/event-stream is not working

[talasila-sairam]

Versions That i have used
Java:- OpenJDK-11
Spring boot: 2.7.0
reactor-core: 3.4.28
netty: 1.0.30

Problem: I created a custom actuator endpoint to expose a data stream, however despite events being triggered, requests are taking a long time to complete and no data is being released.

This is my simple controller

I noticed that, while the same configuration functions perfectly when using the restController, it does not function when using the endpoint and readOperation annotation.

[bclozel]

Sorry but Spring Boot 2.7.x is out of open source support. We can reopen this issue if you provide a minimal sample that reproduces the problem on a supported version (3.2.x+). See https://spring.io/projects/spring-boot#support

Thanks!

[talasila-sairam]

resilience4j-spring-boot3-demo.zip
Hey @bclozel and @wilkinsona
I've attached a zip file including all of my project files. Please let me know if you require anything else.

[wilkinsona]

Thanks, @talasila-sairam. Unfortunately, there are really too many moving parts in that code for us to start looking at it. As I said on #42475, please reduce it to the bare minimum that's required to reproduce the problem. As I understand the problem, that should be dependencies on only the actuator and webflux starters and a single custom endpoint that uses text/event-stream.

[wilkinsona]

Actually, on second look, I'm not surprised that this doesn't work. You're using ServerSentEvent that is, quoting from its javadoc, "for use with Spring's reactive Web support". You're not (directly) using Spring's reactive web support here, you're using the Actuator's endpoint infrastructure which is an abstraction on top of Spring MVC, Spring WebFlux, and Jersey. As such, you should not expect features for use with WebFlux to work.

You may be able to use @RestControllerEndpoint instead. This couples your endpoint to Spring MVC or Spring WebFlux. Note that it has been deprecated since Spring Boot 3.3.x as we intend to tighten up Actuator's endpoint infrastructure in Spring Boot 4 and only support higher-level concepts that can be mapped to all three web frameworks that we support.

[talasila-sairam]

• Thank you for your response. Is there any way to obtain the events using the actuator endpoint in this scenario?similar to produces for an actuator endpoint should be text/event-stream. is that possible?
• What is being obsoleted in this instance? I did't get that point.

[wilkinsona]

Is there any way to obtain the events using the actuator endpoint in this scenario?similar to produces for an actuator endpoint should be text/event-stream

You may be able to use @RestControllerEndpoint as I mentioned above.

What is being obsoleted in this instance? I did't get that point.

Please see #31768.

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