Improve error handling when response is committed

ResponseStatusExceptionHandler lets the error through if it can't
change the status while HttpWebHandlerAdapter logs a more helpful
message (including status code) but without a full stack trace.

Issue: SPR-16231

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/server/adapter/HttpWebHandlerAdapter.java

@@ -71,7 +71,7 @@ public class HttpWebHandlerAdapter extends WebHandlerDecorator implements HttpHa
 	 * <p>TODO:
 	 * This definition is currently duplicated between HttpWebHandlerAdapter
 	 * and AbstractSockJsSession. It is a candidate for a common utility class.
-	 * @see #indicatesDisconnectedClient(Throwable)
+	 * @see #isDisconnectedClientError(Throwable)
 	 */
 	private static final Set<String> DISCONNECTED_CLIENT_EXCEPTIONS =
 			new HashSet<>(Arrays.asList("ClientAbortException", "EOFException", "EofException"));
@@ -158,8 +158,7 @@ public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response)
 		ServerWebExchange exchange = createExchange(request, response);
 		return getDelegate().handle(exchange)
 				.onErrorResume(ex -> {
-					response.setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
-					logHandleFailure(ex);
+					handleFailure(response, ex);
 					return Mono.empty();
 				})
 				.then(Mono.defer(response::setComplete));
@@ -170,8 +169,9 @@ protected ServerWebExchange createExchange(ServerHttpRequest request, ServerHttp
 				getCodecConfigurer(), getLocaleContextResolver());
 	}
 
-	private void logHandleFailure(Throwable ex) {
-		if (indicatesDisconnectedClient(ex)) {
+	private void handleFailure(ServerHttpResponse response, Throwable ex) {
+		boolean statusCodeChanged = response.setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
+		if (isDisconnectedClientError(ex)) {
 			if (disconnectedClientLogger.isTraceEnabled()) {
 				disconnectedClientLogger.trace("Looks like the client has gone away", ex);
 			}
@@ -181,12 +181,16 @@ else if (disconnectedClientLogger.isDebugEnabled()) {
 						"' to TRACE level.)");
 			}
 		}
+		else if (!statusCodeChanged) {
+			logger.error("Unhandled failure: " + ex.getMessage() + ", " +
+					"response already committed with status=" + response.getStatusCode());
+		}
 		else {
 			logger.error("Failed to handle request", ex);
 		}
 	}
 
-	private boolean indicatesDisconnectedClient(Throwable ex)  {
+	private boolean isDisconnectedClientError(Throwable ex)  {
 		String message = NestedExceptionUtils.getMostSpecificCause(ex).getMessage();
 		message = (message != null ? message.toLowerCase() : "");
 		String className = ex.getClass().getSimpleName();

spring-web/src/main/java/org/springframework/web/server/handler/ResponseStatusExceptionHandler.java

@@ -20,6 +20,7 @@
 import org.apache.commons.logging.LogFactory;
 import reactor.core.publisher.Mono;
 
+import org.springframework.http.HttpStatus;
 import org.springframework.web.server.ResponseStatusException;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebExceptionHandler;
@@ -39,10 +40,11 @@ public class ResponseStatusExceptionHandler implements WebExceptionHandler {
 	@Override
 	public Mono<Void> handle(ServerWebExchange exchange, Throwable ex) {
 		if (ex instanceof ResponseStatusException) {
-			// Response may be committed but we'll try..
-			logger.debug(ex.getMessage());
-			exchange.getResponse().setStatusCode(((ResponseStatusException) ex).getStatus());
-			return exchange.getResponse().setComplete();
+			HttpStatus status = ((ResponseStatusException) ex).getStatus();
+			if (exchange.getResponse().setStatusCode(status)) {
+				logger.trace(ex.getMessage());
+				return exchange.getResponse().setComplete();
+			}
 		}
 		return Mono.error(ex);
 	}

spring-web/src/test/java/org/springframework/web/server/handler/ResponseStatusExceptionHandlerTests.java

@@ -59,10 +59,9 @@ public void unresolvedException() throws Exception {
 	public void responseCommitted() throws Exception {
 		Throwable ex = new ResponseStatusException(HttpStatus.INTERNAL_SERVER_ERROR, "Oops");
 		this.exchange.getResponse().setStatusCode(HttpStatus.CREATED);
-		this.exchange.getResponse().setComplete()
-				.then(this.handler.handle(this.exchange, ex))
-				.block(Duration.ofSeconds(5));
-		assertEquals(HttpStatus.CREATED, this.exchange.getResponse().getStatusCode());
+		Mono<Void> mono = this.exchange.getResponse().setComplete()
+				.then(this.handler.handle(this.exchange, ex));
+		StepVerifier.create(mono).consumeErrorWith(actual -> assertSame(ex, actual)).verify();
 	}
 
 }