We have been tracking rather strange & random failures in our application: eventually, after many browser closed (and/or page refresh), our SSE event flux would not be sending anything anymore to new clients.

We identified that threads used for async tasks execution (AsyncSupportConfigurer) may deadlock due to a timing-dependant ABBA deadlock between SseEmitter sending and error handling on connection closed. If using the the default SimpleAsyncTaskExecutor which fires up a new Thread for each task, no user visible effect (except that some deadlocked unused threads are consumming resources on the server). But, if using a fixed number of threads (as we do in our application), the system may finally come to a halt (when all worker threads have been deadlocked).

What we think is going on (see example jstack trace captured):

The client is connected to the SSE endpoint:
For an object to be written to the sse flux:
- the SseEmitter locks itself (synchronized on super.send(...))
- then the Object is serialized (Jackson)
- eventually, writing/flushing on the output stream will require StandardServletAsyncWebRequest to aquire its stateLock ReentrantLock
The client disconnects abruptly (browser closed), while the object is being serialized:
- the server "sees" that the connection has been closed (probably because another object is sent concurrently on the SseEmitter)
- this triggers StandardServletAsyncWebRequest.onError handling process that first locks the stateLock ReentrantLock and then calls SseEmitter.completeWithError which wants to lock itself (synchronized) So, we think that there's a potential ABBA deadlock between SSE error handling and concurrent SSE sending.

Things are highly timing dependent, but we have been able to reproduce (with high probablity) our observed deadlocks: the idea is to emit big JSON objects (increasing the concurrency window) and normal objects concurrenty on the flux, while closing the browser

Reproduced with spring boot 3.3.2 (springframework 6.1.11) and also 3.3.3 (springframework 6.1.12)

Steps to reproduce:

See the minimalist example attached, with the following steps to reproduce:

Launch the main class
- note the process PID for further reference
Using a browser as an http client, go to the index.html via url : http://localhost:8080
Refresh the browser
Run the "jstack $PID" command
- You should notice 1 deadlock (varying probability, but still very likely)
For each additional refresh, an additional deadlock may appear

Example of deadlock captured using jstack:

Found one Java-level deadlock:
=============================
"http-nio-8080-exec-3":
  waiting to lock monitor 0x000001dfe2866ac0 (object 0x0000000614fc1408, a org.springframework.web.servlet.mvc.method.annotation.SseEmitter),
  which is held by "task-4"

"task-4":
  waiting for ownable synchronizer 0x0000000614e998c0, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),
  which is held by "http-nio-8080-exec-3"

Java stack information for the threads listed above:
===================================================
"http-nio-8080-exec-3":
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter.completeWithError(ResponseBodyEmitter.java:264)
    - waiting to lock <0x0000000614fc1408> (a org.springframework.web.servlet.mvc.method.annotation.SseEmitter)
    at org.springframework.web.servlet.mvc.method.annotation.ReactiveTypeHandler$AbstractEmitterSubscriber$$Lambda/0x000001df9d4acaf0.accept(Unknown Source)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter$ErrorCallback.accept(ResponseBodyEmitter.java:396)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter$ErrorCallback.accept(ResponseBodyEmitter.java:383)
    at org.springframework.web.context.request.async.DeferredResult$1.handleError(DeferredResult.java:319)
    at org.springframework.web.context.request.async.DeferredResultInterceptorChain.triggerAfterError(DeferredResultInterceptorChain.java:99)
    at org.springframework.web.context.request.async.WebAsyncManager.lambda$startDeferredResultProcessing$6(WebAsyncManager.java:451)
    at org.springframework.web.context.request.async.WebAsyncManager$$Lambda/0x000001df9d4b0220.accept(Unknown Source)
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest.lambda$onError$0(StandardServletAsyncWebRequest.java:193)
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest$$Lambda/0x000001df9d4c1970.accept(Unknown Source)
    at java.util.ArrayList.forEach(java.base@21.0.3/ArrayList.java:1596)
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest.onError(StandardServletAsyncWebRequest.java:193)
    at org.apache.catalina.core.AsyncListenerWrapper.fireOnError(AsyncListenerWrapper.java:49)
    at org.apache.catalina.core.AsyncContextImpl.setErrorState(AsyncContextImpl.java:415)
    at org.apache.catalina.connector.CoyoteAdapter.asyncDispatch(CoyoteAdapter.java:155)
    at org.apache.coyote.AbstractProcessor.dispatch(AbstractProcessor.java:243)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:57)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:904)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1741)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1190)
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63)
    at java.lang.Thread.runWith(java.base@21.0.3/Thread.java:1596)
    at java.lang.Thread.run(java.base@21.0.3/Thread.java:1583)
"task-4":
    at jdk.internal.misc.Unsafe.park(java.base@21.0.3/Native Method)
    - parking to wait for  <0x0000000614e998c0> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
    at java.util.concurrent.locks.LockSupport.park(java.base@21.0.3/LockSupport.java:221)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(java.base@21.0.3/AbstractQueuedSynchronizer.java:754)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(java.base@21.0.3/AbstractQueuedSynchronizer.java:990)
    at java.util.concurrent.locks.ReentrantLock$Sync.lock(java.base@21.0.3/ReentrantLock.java:153)
    at java.util.concurrent.locks.ReentrantLock.lock(java.base@21.0.3/ReentrantLock.java:322)
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest$LifecycleHttpServletResponse.obtainLockAndCheckState(StandardServletAsyncWebRequest.java:306)
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest$LifecycleServletOutputStream.write(StandardServletAsyncWebRequest.java:373)
    at org.springframework.util.StreamUtils$NonClosingOutputStream.write(StreamUtils.java:261)
    at com.fasterxml.jackson.core.json.UTF8JsonGenerator._flushBuffer(UTF8JsonGenerator.java:2210)
    at com.fasterxml.jackson.core.json.UTF8JsonGenerator.close(UTF8JsonGenerator.java:1234)
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:452)
    at org.springframework.http.converter.AbstractGenericHttpMessageConverter.writeInternal(AbstractGenericHttpMessageConverter.java:123)
    at org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:235)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitterReturnValueHandler$HttpMessageConvertingHandler.sendInternal(ResponseBodyEmitterReturnValueHandler.java:221)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitterReturnValueHandler$HttpMessageConvertingHandler.send(ResponseBodyEmitterReturnValueHandler.java:212)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter.sendInternal(ResponseBodyEmitter.java:223)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter.send(ResponseBodyEmitter.java:214)
    - locked <0x0000000614fc1408> (a org.springframework.web.servlet.mvc.method.annotation.SseEmitter)
    at org.springframework.web.servlet.mvc.method.annotation.SseEmitter.send(SseEmitter.java:135)
    at org.springframework.web.servlet.mvc.method.annotation.ReactiveTypeHandler$SseEmitterSubscriber.send(ReactiveTypeHandler.java:389)
    at org.springframework.web.servlet.mvc.method.annotation.ReactiveTypeHandler$AbstractEmitterSubscriber.run(ReactiveTypeHandler.java:332)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@21.0.3/ThreadPoolExecutor.java:1144)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@21.0.3/ThreadPoolExecutor.java:642)
    at java.lang.Thread.runWith(java.base@21.0.3/Thread.java:1596)
    at java.lang.Thread.run(java.base@21.0.3/Thread.java:1583)

Found 1 deadlock.

demodeadlock.zip

Thank you for the investigation. This looks like a valid issue.

I pushed a fix 3d1bf28445e80ff8428d62556560143275f1e548, but I was not able to reproduce the condition with the demo. Possibly related, after the index page loads, this appears in the logs:

reactor.core.Exceptions$OverflowException: Could not emit tick 32 due to lack of requests (interval doesn't support small downstream requests that replenish slower than the ticks)

If you could give it a try with 6.1.13-SNAPSHOT to confirm the fix that would be very helpful.

I tried with 6.1.13-SNAPSHOT and can not reproduce anymore with the demo (and reloading quickly many times in a row) (note: I think adding onBackpressureLatest() on the 2 fluxes avoids the OverflowException).

Still, there's this scary warning in the logs:

2024-09-16T15:14:59.016+02:00  WARN 24584 --- [io-8080-exec-10] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.context.request.async.AsyncRequestNotUsableException: ServletOutputStream failed to write: java.io.IOException: An established connection was aborted by the software in your host machine]
Exception in thread "task-21" java.lang.IllegalStateException: A non-container (application) thread attempted to use the AsyncContext after an error had occurred and the call to AsyncListener.onError() had returned. This is not allowed to avoid race conditions.
    at org.apache.catalina.core.AsyncContextImpl.check(AsyncContextImpl.java:537)
    at org.apache.catalina.core.AsyncContextImpl.getRequest(AsyncContextImpl.java:211)
    at org.apache.catalina.core.AsyncContextImpl.dispatch(AsyncContextImpl.java:201)
    at org.apache.catalina.core.AsyncContextImpl.dispatch(AsyncContextImpl.java:176)
    at org.apache.catalina.core.AsyncContextImpl.dispatch(AsyncContextImpl.java:170)
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest.dispatch(StandardServletAsyncWebRequest.java:170)
    at org.springframework.web.context.request.async.WebAsyncManager.setConcurrentResultAndDispatch(WebAsyncManager.java:411)
    at org.springframework.web.context.request.async.WebAsyncManager.lambda$startDeferredResultProcessing$8(WebAsyncManager.java:489)
    at org.springframework.web.context.request.async.DeferredResult.setResultInternal(DeferredResult.java:272)
    at org.springframework.web.context.request.async.DeferredResult.setErrorResult(DeferredResult.java:287)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitterReturnValueHandler$HttpMessageConvertingHandler.completeWithError(ResponseBodyEmitterReturnValueHandler.java:241)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter.completeWithError(ResponseBodyEmitter.java:267)
    at org.springframework.web.servlet.mvc.method.annotation.ReactiveTypeHandler$AbstractEmitterSubscriber.run(ReactiveTypeHandler.java:340)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
    at java.base/java.lang.Thread.run(Thread.java:1583)

Thanks for the feedback and by the way 6.1.13 was released in the mean time.

For the new stacktrace, I have looked at the source code and cannot understand why or how this can happen. On the original stacktrace, the "task-4" thread is on line 332 of ReactiveTypeHandler trying to send the message, but gets stuck waiting on the state lock of StandardServletAsyncWebRequest. After the fix, it no longer waits indefinitely but keeps checking if the state changed and indicates an onError notification (in progress). That should result in AsyncRequestNotUsableException being thrown, eventually making its way to line 340 in ReactiveTypeHandler in the new stacktrace where the exception is handled by completing the SseEmitter.

In order for the dispatch on line 411 of WebAsyncManager in the new stacktrace to occur, it would have to pass the state check on line 388, which is protected with a synchronized block on WebAsyncManager.this and there should be only one such instance per request. The onError handling also passes through this method, so if it had passed first as the IllegalStateException says, it would have changed the state to RESULT_SET, and therefore the next thread to pass should exit early and not call dispatch. I don't see how this protection can fail, and therefore whether there is an issue at the level of Tomcat with how it makes this determination.

For the AsyncRequestNotUsableException on Servlet container thread "io-8080-exec-10", do you have any idea whether that's for the same request as the IllegalStateException? If so that would imply the onError handling called dispatch first and reached DefaultHandlerExceptionResolver. However, I would expect in that case the exception to be a Tomcat specific IOException. A more likely explanation is that it is for a different request where the AsyncRequestNotUsableException from SseEmitter succeeded in calling dispatch first.

I will try the example again to see if I have better luck, but it would help to see a full stacktrace for the exception. You could try DEBUG level logging for org.springframework.web, or an @ExceptionHandler to log it.

Below the full stacktrace (with 6.6.13, a similar one was also reproduced with 6.6.12 - so, this is not something new):

2024-09-17T09:07:03.010+02:00 ERROR 11316 --- [nio-8080-exec-3] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] threw exception

java.lang.IllegalStateException: Cannot start async: [ERROR]
    at org.springframework.util.Assert.state(Assert.java:76) ~[spring-core-6.1.13.jar:6.1.13]
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest.startAsync(StandardServletAsyncWebRequest.java:156) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.context.request.async.WebAsyncManager.startAsyncProcessing(WebAsyncManager.java:508) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.context.request.async.WebAsyncManager.startDeferredResultProcessing(WebAsyncManager.java:483) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitterReturnValueHandler.handleReturnValue(ResponseBodyEmitterReturnValueHandler.java:177) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:78) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:136) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:926) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:831) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) ~[tomcat-embed-core-10.1.28.jar:6.0]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.28.jar:6.0]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.13.jar:6.1.13]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-6.1.13.jar:6.1.13]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-6.1.13.jar:6.1.13]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:632) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationDispatcher.doDispatch(ApplicationDispatcher.java:560) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:531) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.AsyncContextImpl$AsyncRunnable.run(AsyncContextImpl.java:601) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.AsyncContextImpl.doInternalDispatch(AsyncContextImpl.java:344) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:165) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:483) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.connector.CoyoteAdapter.asyncDispatch(CoyoteAdapter.java:239) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.coyote.AbstractProcessor.dispatch(AbstractProcessor.java:243) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:57) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:904) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1741) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1190) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]

2024-09-17T09:07:03.033+02:00 ERROR 11316 --- [nio-8080-exec-3] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: java.lang.IllegalStateException: Cannot start async: [ERROR]] with root cause

java.lang.IllegalStateException: Cannot start async: [ERROR]
    at org.springframework.util.Assert.state(Assert.java:76) ~[spring-core-6.1.13.jar:6.1.13]
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest.startAsync(StandardServletAsyncWebRequest.java:156) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.context.request.async.WebAsyncManager.startAsyncProcessing(WebAsyncManager.java:508) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.context.request.async.WebAsyncManager.startDeferredResultProcessing(WebAsyncManager.java:483) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitterReturnValueHandler.handleReturnValue(ResponseBodyEmitterReturnValueHandler.java:177) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:78) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:136) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:926) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:831) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1089) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:979) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:903) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:564) ~[tomcat-embed-core-10.1.28.jar:6.0]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885) ~[spring-webmvc-6.1.13.jar:6.1.13]
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658) ~[tomcat-embed-core-10.1.28.jar:6.0]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:195) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-6.1.13.jar:6.1.13]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116) ~[spring-web-6.1.13.jar:6.1.13]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-6.1.13.jar:6.1.13]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:101) ~[spring-web-6.1.13.jar:6.1.13]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:164) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:140) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:632) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationDispatcher.doDispatch(ApplicationDispatcher.java:560) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:531) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.AsyncContextImpl$AsyncRunnable.run(AsyncContextImpl.java:601) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.AsyncContextImpl.doInternalDispatch(AsyncContextImpl.java:344) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:165) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:483) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:115) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.catalina.connector.CoyoteAdapter.asyncDispatch(CoyoteAdapter.java:239) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.coyote.AbstractProcessor.dispatch(AbstractProcessor.java:243) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:57) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:904) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1741) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1190) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63) ~[tomcat-embed-core-10.1.28.jar:10.1.28]
    at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]

2024-09-17T09:07:03.777+02:00  WARN 11316 --- [nio-8080-exec-7] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.context.request.async.AsyncRequestNotUsableException: ServletOutputStream failed to write: java.io.IOException: An established connection was aborted by the software in your host machine]
Exception in thread "task-1" java.lang.IllegalStateException: A non-container (application) thread attempted to use the AsyncContext after an error had occurred and the call to AsyncListener.onError() had returned. This is not allowed to avoid race conditions.
    at org.apache.catalina.core.AsyncContextImpl.check(AsyncContextImpl.java:537)
    at org.apache.catalina.core.AsyncContextImpl.getRequest(AsyncContextImpl.java:211)
    at org.apache.catalina.core.AsyncContextImpl.dispatch(AsyncContextImpl.java:201)
    at org.apache.catalina.core.AsyncContextImpl.dispatch(AsyncContextImpl.java:176)
    at org.apache.catalina.core.AsyncContextImpl.dispatch(AsyncContextImpl.java:170)
    at org.springframework.web.context.request.async.StandardServletAsyncWebRequest.dispatch(StandardServletAsyncWebRequest.java:170)
    at org.springframework.web.context.request.async.WebAsyncManager.setConcurrentResultAndDispatch(WebAsyncManager.java:411)
    at org.springframework.web.context.request.async.WebAsyncManager.lambda$startDeferredResultProcessing$8(WebAsyncManager.java:489)
    at org.springframework.web.context.request.async.DeferredResult.setResultInternal(DeferredResult.java:272)
    at org.springframework.web.context.request.async.DeferredResult.setErrorResult(DeferredResult.java:287)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitterReturnValueHandler$HttpMessageConvertingHandler.completeWithError(ResponseBodyEmitterReturnValueHandler.java:241)
    at org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter.completeWithError(ResponseBodyEmitter.java:267)
    at org.springframework.web.servlet.mvc.method.annotation.ReactiveTypeHandler$AbstractEmitterSubscriber.run(ReactiveTypeHandler.java:340)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
    at java.base/java.lang.Thread.run(Thread.java:1583)
2024-09-17T09:07:04.303+02:00  WARN 11316 --- [nio-8080-exec-4] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.context.request.async.AsyncRequestNotUsableException: ServletOutputStream failed to write: java.io.IOException: An established connection was aborted by the software in your host machine]
2024-09-17T09:07:04.477+02:00  WARN 11316 --- [nio-8080-exec-5] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.context.request.async.AsyncRequestNotUsableException: ServletOutputStream failed to flush: java.io.IOException: An established connection was aborted by the software in your host machine]

spring-projects / spring-framework

Deadlock between SseEmitter and StandardServletAsyncWebRequest when clients disconnect #33421

Steps to reproduce:

Example of deadlock captured using jstack: