Dispatch again after disconnected client error

Dispatching was prevented for disconnected client errors after
recent reports like #32042 when running on Tomcat, and the
async request was completed from the onError notification.
This has the side effect of not allowing exception resolvers
to take final action even if the response is not writeable.

After all updates for this issue, it appears the dispatch no
longer causes issues. Tomcat actually does not do the dispatch,
but it doesn't seem to cause any issues, and on other servers
like Jetty where the dispatch works, applications can have a
chance to handle the exception.

This change removes the disconnected client checks and allows
dispatching again. After the change DisconnectedClientHelper
is no longer needed in the 5.3.x branch.

See gh-32342

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/context/request/async/StandardServletAsyncWebRequest.java

@@ -34,7 +34,6 @@
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.context.request.ServletWebRequest;
-import org.springframework.web.util.DisconnectedClientHelper;
 
 /**
  * A Servlet implementation of {@link AsyncWebRequest}.
@@ -184,13 +183,6 @@ public void onError(AsyncEvent event) throws IOException {
 			transitionToErrorState();
 			Throwable ex = event.getThrowable();
 			this.exceptionHandlers.forEach(consumer -> consumer.accept(ex));
-
-			// We skip ASYNC dispatches for "disconnected client" errors,
-			// but can only complete from a Servlet container thread
-
-			if (DisconnectedClientHelper.isClientDisconnectedException(ex) && this.state != State.COMPLETED) {
-				this.asyncContext.complete();
-			}
 		}
 		finally {
 			this.stateLock.unlock();

spring-web/src/main/java/org/springframework/web/context/request/async/WebAsyncManager.java

@@ -36,7 +36,6 @@
 import org.springframework.util.Assert;
 import org.springframework.web.context.request.RequestAttributes;
 import org.springframework.web.context.request.async.DeferredResult.DeferredResultHandler;
-import org.springframework.web.util.DisconnectedClientHelper;
 
 /**
  * The central class for managing asynchronous request processing, mainly intended
@@ -70,16 +69,6 @@ public final class WebAsyncManager {
 
 	private static final Log logger = LogFactory.getLog(WebAsyncManager.class);
 
-	/**
-	 * Log category to use for network failure after a client has gone away.
-	 * @see DisconnectedClientHelper
-	 */
-	private static final String DISCONNECTED_CLIENT_LOG_CATEGORY =
-			"org.springframework.web.server.DisconnectedClient";
-
-	private static final DisconnectedClientHelper disconnectedClientHelper =
-			new DisconnectedClientHelper(DISCONNECTED_CLIENT_LOG_CATEGORY);
-
 	private static final CallableProcessingInterceptor timeoutCallableInterceptor =
 			new TimeoutCallableProcessingInterceptor();
 
@@ -418,12 +407,6 @@ private void setConcurrentResultAndDispatch(@Nullable Object result) {
 				logger.debug("Async result set to: " + result + " for " + formatUri(this.asyncWebRequest));
 			}
 
-			if (result instanceof Exception) {
-				if (disconnectedClientHelper.checkAndLogClientDisconnectedException((Exception) result)) {
-					return;
-				}
-			}
-
 			if (this.asyncWebRequest.isAsyncComplete()) {
 				if (logger.isDebugEnabled()) {
 					logger.debug("Async request already completed for " + formatUri(this.asyncWebRequest));

spring-web/src/main/java/org/springframework/web/util/DisconnectedClientHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,6 +46,7 @@
 import org.springframework.web.bind.annotation.ModelAttribute;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestPart;
+import org.springframework.web.context.request.async.AsyncRequestNotUsableException;
 import org.springframework.web.context.request.async.AsyncRequestTimeoutException;
 import org.springframework.web.multipart.MultipartFile;
 import org.springframework.web.multipart.support.MissingServletRequestPartException;
@@ -228,6 +229,10 @@ else if (ex instanceof AsyncRequestTimeoutException) {
 				return handleAsyncRequestTimeoutException(
 						(AsyncRequestTimeoutException) ex, request, response, handler);
 			}
+			else if (ex instanceof AsyncRequestNotUsableException) {
+				return handleAsyncRequestNotUsableException(
+						(AsyncRequestNotUsableException) ex, request, response, handler);
+			}
 		}
 		catch (Exception handlerEx) {
 			if (logger.isWarnEnabled()) {
@@ -541,6 +546,24 @@ protected ModelAndView handleAsyncRequestTimeoutException(AsyncRequestTimeoutExc
 		return new ModelAndView();
 	}
 
+	/**
+	 * Handle the case of an I/O failure from the ServletOutputStream.
+	 * <p>By default, do nothing since the response is not usable.
+	 * @param ex the {@link AsyncRequestTimeoutException} to be handled
+	 * @param request current HTTP request
+	 * @param response current HTTP response
+	 * @param handler the executed handler, or {@code null} if none chosen
+	 * at the time of the exception (for example, if multipart resolution failed)
+	 * @return an empty ModelAndView indicating the exception was handled
+	 * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
+	 * @since 5.3.33
+	 */
+	protected ModelAndView handleAsyncRequestNotUsableException(AsyncRequestNotUsableException ex,
+			HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) {
+
+		return new ModelAndView();
+	}
+
 	/**
 	 * Invoked to send a server error. Sets the status to 500 and also sets the
 	 * request attribute "javax.servlet.error.exception" to the Exception.

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/support/DefaultHandlerExceptionResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -92,6 +92,9 @@ public void supportsAllDefaultHandlerExceptionResolverExceptionTypes() throws Ex
 			Class<?>[] paramTypes = method.getParameterTypes();
 			if (method.getName().startsWith("handle") && (paramTypes.length == 4)) {
 				String name = paramTypes[0].getSimpleName();
+				if (name.equals("AsyncRequestNotUsableException")) {
+					continue;
+				}
 				assertThat(exceptionTypes.contains(paramTypes[0])).as("@ExceptionHandler is missing " + name).isTrue();
 			}
 		}