Custom handler for OOM error

[typik89]

How can I handle "java.lang.OutOfMemoryError: Java heap space" in reactor?(https://stackoverflow.com/questions/71016578/how-can-i-handle-java-lang-outofmemoryerror-java-heap-space-in-reactor)

I implemented my simple rest endpoint using reactor and Webflux: https://github.com/typik89/webfluxMemoryRetroProject.
As a result of HTTP GET requests It requests data from a database and creates a file with a size of about 70MB. So If I run it with -xmx100m, I have only an error in logs:
2022-02-07 12:25:06.135 ERROR 10288 --- [actor-tcp-nio-1] r.n.channel.ChannelOperationsHandler : [7edd71ea, L:/127.0.0.1:58918 - R:localhost/127.0.0.1:5432] Error was received while reading the incoming data. The connection will be closed. java.lang.OutOfMemoryError: Java heap space .... 2022-02-07 12:25:06.141 ERROR 10288 --- [actor-tcp-nio-1] i.r.p.client.ReactorNettyClient : Connection Error reactor.netty.ReactorNetty$InternalNettyException: java.lang.OutOfMemoryError: Java heap space
This error isn't handled and an HTTP client request hangs. Is this expected behavior? how can I handle this exception? I've tried onErrorResume and Hooks.onOperatorError but I couldn't intercept this type of exception. It seems unlogical for me that the application keeps working and I can't intercept and handle such errors

[simonbasle]

as stated in the StackOverflow question comments, once you get an OutOfMemoryError, you're in uncharted territory.
This is a VirtualMachineError, which are described as:

Thrown to indicate that the Java Virtual Machine is broken or has run out of resources necessary for it to continue operating.

Your application is potentially in an unrecoverable state, and the fact that it seem to continue working is not a guarantee that it will continue working.

For that reason, OutOfMemoryError is among the type of exceptions that Reactor doesn't even try to process through the Reactive Streams onError signal. See Exceptions.throwIfJvmFatal.

(marking as invalid/for/stackoverflow because as mentioned in the guidelines for contributing, we prefer to use GitHub issues only for bugs and enhancements)

[typik89]

@simonbasle , Yes, I totally agree about OOM error and JVM. BUT I see the error in logs and you intercept it. Why I can't customize handling.
Maybe via Hooks class. It's unlogical for me, I would prefer that my application goes down in this case because as you said that it's potentially in an unrecoverable state. But my application keeps working and handling requests in this states and all probes work