Error using Spring cloud gateway - IllegalStateException: channel not registered to an event loop - Client waits infinite for response

[FrankKlOS]

We have noticed occasionally the following exception in our logs:

dmssidecar.7301           : 2024-12-22T15:34:54.038+01:00  WARN 30048 --- [dms] [ctor-http-nio-5] i.n.u.concurrent.AbstractEventExecutor   : A task raised an exception. Task: reactor.netty.channel.FluxReceive$$Lambda$2120/0x000001c60190c3c8@7dc94a20
dmssidecar.7301           : 
dmssidecar.7301           : java.lang.IllegalStateException: channel not registered to an event loop
dmssidecar.7301           : 	at io.netty.channel.AbstractChannel.eventLoop(AbstractChannel.java:163)
dmssidecar.7301           : 	at io.netty.channel.AbstractChannelHandlerContext.executor(AbstractChannelHandlerContext.java:132)
dmssidecar.7301           : 	at io.netty.channel.AbstractChannelHandlerContext.findContextOutbound(AbstractChannelHandlerContext.java:1079)
dmssidecar.7301           : 	at io.netty.channel.AbstractChannelHandlerContext.read(AbstractChannelHandlerContext.java:821)
dmssidecar.7301           : 	at io.netty.channel.DefaultChannelPipeline.read(DefaultChannelPipeline.java:953)
dmssidecar.7301           : 	at io.netty.channel.AbstractChannel.read(AbstractChannel.java:289)
dmssidecar.7301           : 	at io.netty.channel.DefaultChannelConfig.setAutoRead(DefaultChannelConfig.java:341)
dmssidecar.7301           : 	at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:338)
dmssidecar.7301           : 	at reactor.netty.channel.FluxReceive.lambda$request$1(FluxReceive.java:136)
dmssidecar.7301           : 	at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:173)
dmssidecar.7301           : 	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:166)
dmssidecar.7301           : 	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:472)
dmssidecar.7301           : 	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:569)
dmssidecar.7301           : 	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
dmssidecar.7301           : 	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
dmssidecar.7301           : 	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
dmssidecar.7301           : 	at java.base/java.lang.Thread.run(Thread.java:840)

If this exeption occures, the client call gets stalled. If a socket timeout is not set, the client waits infinite for a response. This results in some of our services not starting up or failing during runtime.

Expected Behavior

The call should succeed and the spring cloud gateway should forward the request.

Actual Behavior

The request gets stalled. The gateway never returns. This does not happen on every request - but around 2-3% fail.

Steps to Reproduce

A multithreaded test http client was used to reproduce the behaviour. Should be reproducable with any http load testframework.

Possible Solution

Use version 1.1.23 of reactor-netty. The problem does not occure in this version. The error behaviour can be reproduced in 1.1.24 and 1.1.25. Only the reactory-netty-core library was replaced for the test. All other libraries in our app stayed the same. The reactor-netty version was enforced in the app main pom. The 1.2.x branch was not tested.

Your Environment

• Reactor version(s) used: reactor-netty-core 1.1.24 + 1.1.25. Version 1.1.23 is working.
• Other relevant libraries versions (eg. netty, ...): Spring cloud version 2023.0.3 + Spring-boot 3.3.6.
• JVM version (java -version): 17.0.1+12-LTS-39
• OS and version (eg. uname -a): Windows Server 2019

[lotmek]

We started facing the same issue in Spring Cloud Gateway when Renovate Bot upgraded Spring Boot version from 3.2.11 to 3.2.12. It seems to happen only with large or chunked requests.

I wonder if it was introduced with this PR #3459

[violetagg]

@FrankKlOS Thanks for the detailed description. This is fixed with #3581. It would be great if you can test the snapshot version.

[FrankKlOS]

@FrankKlOS Thanks for the detailed description. This is fixed with #3581. It would be great if you can test the snapshot version.

Hi - I have tested with a locally build 1.2.2-SNAPSHOT version of reactor-netty and can confirm that the error goes away. Thanks for your fix.

[violetagg]

@FrankKlOS Thanks for the detailed description. This is fixed with #3581. It would be great if you can test the snapshot version.

Hi - I have tested with a locally build 1.2.2-SNAPSHOT version of reactor-netty and can confirm that the error goes away. Thanks for your fix.

Thanks