Ensure ISE will not be thrown when the client disconnects

[violetagg]

• ServletServerHttpResponse.ResponseAsyncListener#onError/onTimeout
  must complete the async operation
• ServletHttpHandlerAdapter.HandlerResultSubscriber#onComplete must
  check that the async operation is not completed

Issue: SPR-15412

[rstoyanchev]

The change is merged with some minor polish in a follow-up commit. Please have a look, hopefully didn't break anything inadvertently.

What I'm also wondering is whether the issue can occur the other way around. In other words for the onError signal from the ResponseAsyncListener to reach the HandlerResultSubscriber, which also completes the AsyncContext, first.

[violetagg]

What I'm also wondering is whether the issue can occur the other way around. In other words for the onError signal from the ResponseAsyncListener to reach the HandlerResultSubscriber, which also completes the AsyncContext, first.

Yes you are right. I reproduced it with a debugger.

java.lang.IllegalStateException: Calling [asyncComplete()] is not valid for a request with Async state [MUST_COMPLETE]	at org.apache.coyote.AsyncStateMachine.doComplete(AsyncStateMachine.java:304) ~[tomcat-embed-core-8.5.13.jar!/:8.5.13]	at org.apache.coyote.AsyncStateMachine.asyncComplete(AsyncStateMachine.java:289) ~[tomcat-embed-core-8.5.13.jar!/:8.5.13]	at org.apache.coyote.AbstractProcessor.action(AbstractProcessor.java:373) [tomcat-embed-core-8.5.13.jar!/:8.5.13]	at org.apache.coyote.Request.action(Request.java:391) ~[tomcat-embed-core-8.5.13.jar!/:8.5.13]	at org.apache.catalina.core.AsyncContextImpl.complete(AsyncContextImpl.java:95) ~[tomcat-embed-core-8.5.13.jar!/:8.5.13]	at org.springframework.http.server.reactive.ServletServerHttpResponse$ResponseAsyncListener.onError(ServletServerHttpResponse.java:189) ~[spring-web-5.0.0.BUILD-SNAPSHOT.jar!/:5.0.0.BUILD-SNAPSHOT 

So we need a check also for ServletHttpHandlerAdapter.TIMEOUT_LISTENER.onError/onTimeout (the new code after polishing)

[rstoyanchev]

Okay thanks, I'll combine then HandlerResultSubscriber and TIMEOUT_LISTENER into one so they can share these checks.

[rstoyanchev]

Okay should be fixed now.