Extra information in WebFlux stacktraces

Use the checkpoint operator at various places in WebFlux to insert
information that Reactor then uses to enrich exceptions, via suppressed
exceptions, when error signals flow through the operator.

Closes gh-22105

spring-web/src/main/java/org/springframework/web/method/HandlerMethod.java

@@ -21,6 +21,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.StringJoiner;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
@@ -89,6 +90,8 @@ public class HandlerMethod {
 	@Nullable
 	private volatile List<Annotation[][]> interfaceParameterAnnotations;
 
+	private final String description;
+
 
 	/**
 	 * Create an instance from a bean instance and a method.
@@ -103,6 +106,7 @@ public HandlerMethod(Object bean, Method method) {
 		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
 		this.parameters = initMethodParameters();
 		evaluateResponseStatus();
+		this.description = initDescription(this.beanType, this.method);
 	}
 
 	/**
@@ -119,6 +123,7 @@ public HandlerMethod(Object bean, String methodName, Class<?>... parameterTypes)
 		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(this.method);
 		this.parameters = initMethodParameters();
 		evaluateResponseStatus();
+		this.description = initDescription(this.beanType, this.method);
 	}
 
 	/**
@@ -141,6 +146,7 @@ public HandlerMethod(String beanName, BeanFactory beanFactory, Method method) {
 		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
 		this.parameters = initMethodParameters();
 		evaluateResponseStatus();
+		this.description = initDescription(this.beanType, this.method);
 	}
 
 	/**
@@ -156,6 +162,7 @@ protected HandlerMethod(HandlerMethod handlerMethod) {
 		this.parameters = handlerMethod.parameters;
 		this.responseStatus = handlerMethod.responseStatus;
 		this.responseStatusReason = handlerMethod.responseStatusReason;
+		this.description = handlerMethod.description;
 		this.resolvedFromHandlerMethod = handlerMethod.resolvedFromHandlerMethod;
 	}
 
@@ -174,6 +181,7 @@ private HandlerMethod(HandlerMethod handlerMethod, Object handler) {
 		this.responseStatus = handlerMethod.responseStatus;
 		this.responseStatusReason = handlerMethod.responseStatusReason;
 		this.resolvedFromHandlerMethod = handlerMethod;
+		this.description = handlerMethod.description;
 	}
 
 	private MethodParameter[] initMethodParameters() {
@@ -198,6 +206,14 @@ private void evaluateResponseStatus() {
 		}
 	}
 
+	private static String initDescription(Class<?> beanType, Method method) {
+		StringJoiner joiner = new StringJoiner(", ", "(", ")");
+		for (Class<?> paramType : method.getParameterTypes()) {
+			joiner.add(paramType.getSimpleName());
+		}
+		return beanType.getName() + "#" + method.getName() + joiner.toString();
+	}
+
 
 	/**
 	 * Return the bean for this handler method.
@@ -389,7 +405,7 @@ public int hashCode() {
 
 	@Override
 	public String toString() {
-		return this.method.toGenericString();
+		return this.description;
 	}
 
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -53,7 +53,7 @@ public class DefaultWebFilterChain implements WebFilterChain {
 	private final WebFilter currentFilter;
 
 	@Nullable
-	private final DefaultWebFilterChain next;
+	private final DefaultWebFilterChain chain;
 
 
 	/**
@@ -68,7 +68,7 @@ public DefaultWebFilterChain(WebHandler handler, List<WebFilter> filters) {
 		this.handler = handler;
 		DefaultWebFilterChain chain = initChain(filters, handler);
 		this.currentFilter = chain.currentFilter;
-		this.next = chain.next;
+		this.chain = chain.chain;
 	}
 
 	private static DefaultWebFilterChain initChain(List<WebFilter> filters, WebHandler handler) {
@@ -84,12 +84,12 @@ private static DefaultWebFilterChain initChain(List<WebFilter> filters, WebHandl
 	 * Private constructor to represent one link in the chain.
 	 */
 	private DefaultWebFilterChain(List<WebFilter> allFilters, WebHandler handler,
-			@Nullable WebFilter currentFilter, @Nullable DefaultWebFilterChain next) {
+			@Nullable WebFilter currentFilter, @Nullable DefaultWebFilterChain chain) {
 
 		this.allFilters = allFilters;
 		this.currentFilter = currentFilter;
 		this.handler = handler;
-		this.next = next;
+		this.chain = chain;
 	}
 
 	/**
@@ -117,9 +117,14 @@ public WebHandler getHandler() {
 	@Override
 	public Mono<Void> filter(ServerWebExchange exchange) {
 		return Mono.defer(() ->
-				this.currentFilter != null && this.next != null ?
-						this.currentFilter.filter(exchange, this.next) :
+				this.currentFilter != null && this.chain != null ?
+						invokeFilter(this.currentFilter, this.chain, exchange) :
 						this.handler.handle(exchange));
 	}
 
+	private Mono<Void> invokeFilter(WebFilter current, DefaultWebFilterChain chain, ServerWebExchange exchange) {
+		return current.filter(exchange, chain)
+				.checkpoint(current.getClass().getName() + " [DefaultWebFilterChain]");
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -22,6 +22,9 @@
 
 import reactor.core.publisher.Mono;
 
+import org.springframework.http.HttpMethod;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.util.StringUtils;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebExceptionHandler;
 import org.springframework.web.server.WebHandler;
@@ -41,7 +44,10 @@ public class ExceptionHandlingWebHandler extends WebHandlerDecorator {
 
 	public ExceptionHandlingWebHandler(WebHandler delegate, List<WebExceptionHandler> handlers) {
 		super(delegate);
-		this.exceptionHandlers = Collections.unmodifiableList(new ArrayList<>(handlers));
+		List<WebExceptionHandler> handlersToUse = new ArrayList<>();
+		handlersToUse.add(new CheckpointInsertingHandler());
+		handlersToUse.addAll(handlers);
+		this.exceptionHandlers = Collections.unmodifiableList(handlersToUse);
 	}
 
 
@@ -71,4 +77,24 @@ public Mono<Void> handle(ServerWebExchange exchange) {
 		return completion;
 	}
 
+
+	/**
+	 * WebExceptionHandler to insert a checkpoint with current URL information.
+	 * Must be the first in order to ensure we catch the error signal before
+	 * the exception is handled and e.g. turned into an error response.
+	 * @since 5.2
+ 	 */
+	private static class CheckpointInsertingHandler implements WebExceptionHandler {
+
+		@Override
+		public Mono<Void> handle(ServerWebExchange exchange, Throwable ex) {
+			ServerHttpRequest request = exchange.getRequest();
+			String rawQuery = request.getURI().getRawQuery();
+			String query = StringUtils.hasText(rawQuery) ? "?" + rawQuery : "";
+			HttpMethod httpMethod = request.getMethod();
+			String description = "HTTP " + httpMethod + " \"" + request.getPath() + query + "\"";
+			return Mono.error(ex).checkpoint(description + " [ExceptionHandlingWebHandler]").cast(Void.class);
+		}
+	}
+
 }

spring-webflux/src/main/java/org/springframework/web/reactive/DispatcherHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -67,11 +67,6 @@
  */
 public class DispatcherHandler implements WebHandler, ApplicationContextAware {
 
-	@SuppressWarnings("ThrowableInstanceNeverThrown")
-	private static final Exception HANDLER_NOT_FOUND_EXCEPTION =
-			new ResponseStatusException(HttpStatus.NOT_FOUND, "No matching handler");
-
-
 	@Nullable
 	private List<HandlerMapping> handlerMappings;
 
@@ -172,8 +167,13 @@ private Mono<HandlerResult> invokeHandler(ServerWebExchange exchange, Object han
 
 	private Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
 		return getResultHandler(result).handleResult(exchange, result)
-				.onErrorResume(ex -> result.applyExceptionHandler(ex).flatMap(exceptionResult ->
-						getResultHandler(exceptionResult).handleResult(exchange, exceptionResult)));
+				.checkpoint("Handler " + result.getHandler() + " [DispatcherHandler]")
+				.onErrorResume(ex ->
+						result.applyExceptionHandler(ex).flatMap(exResult -> {
+							String text = "Exception handler " + exResult.getHandler() +
+									", error=\"" + ex.getMessage() + "\" [DispatcherHandler]";
+							return getResultHandler(exResult).handleResult(exchange, exResult).checkpoint(text);
+						}));
 	}
 
 	private HandlerResultHandler getResultHandler(HandlerResult handlerResult) {

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultClientResponse.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -56,12 +56,17 @@ class DefaultClientResponse implements ClientResponse {
 
 	private final String logPrefix;
 
+	private final String requestDescription;
+
+
+	public DefaultClientResponse(ClientHttpResponse response, ExchangeStrategies strategies,
+			String logPrefix, String requestDescription) {
 
-	public DefaultClientResponse(ClientHttpResponse response, ExchangeStrategies strategies, String logPrefix) {
 		this.response = response;
 		this.strategies = strategies;
 		this.headers = new DefaultHeaders();
 		this.logPrefix = logPrefix;
+		this.requestDescription = requestDescription;
 	}
 
 
@@ -90,22 +95,35 @@ public MultiValueMap<String, ResponseCookie> cookies() {
 		return this.response.getCookies();
 	}
 
+	@SuppressWarnings("unchecked")
 	@Override
 	public <T> T body(BodyExtractor<T, ? super ClientHttpResponse> extractor) {
-		return extractor.extract(this.response, new BodyExtractor.Context() {
+		T result = extractor.extract(this.response, new BodyExtractor.Context() {
 			@Override
 			public List<HttpMessageReader<?>> messageReaders() {
 				return strategies.messageReaders();
 			}
+
 			@Override
 			public Optional<ServerHttpResponse> serverResponse() {
 				return Optional.empty();
 			}
+
 			@Override
 			public Map<String, Object> hints() {
 				return Hints.from(Hints.LOG_PREFIX_HINT, logPrefix);
 			}
 		});
+		String description = "Body from " + this.requestDescription + " [DefaultClientResponse]";
+		if (result instanceof Mono) {
+			return (T) ((Mono<?>) result).checkpoint(description);
+		}
+		else if (result instanceof Flux) {
+			return (T) ((Flux<?>) result).checkpoint(description);
+		}
+		else {
+			return result;
+		}
 	}
 
 	@Override

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultClientResponseBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -136,7 +136,7 @@ public ClientResponse build() {
 		// When building ClientResponse manually, the ClientRequest.logPrefix() has to be passed,
 		// e.g. via ClientResponse.Builder, but this (builder) is not used currently.
 
-		return new DefaultClientResponse(httpResponse, this.strategies, "");
+		return new DefaultClientResponse(httpResponse, this.strategies, "", "");
 	}
 
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java

@@ -316,8 +316,9 @@ public Mono<ClientResponse> exchange() {
 			ClientRequest request = (this.inserter != null ?
 					initRequestBuilder().body(this.inserter).build() :
 					initRequestBuilder().build());
-			return Mono.defer(() -> exchangeFunction.exchange(request))
-					.switchIfEmpty(NO_HTTP_CLIENT_RESPONSE_ERROR);
+			return Mono.defer(() -> exchangeFunction.exchange(request)
+					.checkpoint("Request to " + this.httpMethod.name() + " " + this.uri + " [DefaultWebClient]")
+					.switchIfEmpty(NO_HTTP_CLIENT_RESPONSE_ERROR));
 		}
 
 		private ClientRequest.Builder initRequestBuilder() {
@@ -445,8 +446,8 @@ public <T> Flux<T> bodyToFlux(Class<T> elementType) {
 
 		@Override
 		public <T> Flux<T> bodyToFlux(ParameterizedTypeReference<T> elementType) {
-			return this.responseMono.flatMapMany(response -> handleBody(response,
-					response.bodyToFlux(elementType), mono -> mono.flatMapMany(Flux::error)));
+			return this.responseMono.flatMapMany(response ->
+					handleBody(response, response.bodyToFlux(elementType), mono -> mono.flatMapMany(Flux::error)));
 		}
 
 		private <T extends Publisher<?>> T handleBody(ClientResponse response,
@@ -459,7 +460,8 @@ private <T extends Publisher<?>> T handleBody(ClientResponse response,
 						Mono<? extends Throwable> exMono = handler.apply(response, request);
 						exMono = exMono.flatMap(ex -> drainBody(response, ex));
 						exMono = exMono.onErrorResume(ex -> drainBody(response, ex));
-						return errorFunction.apply(exMono);
+						T result = errorFunction.apply(exMono);
+						return insertCheckpoint(result, response.statusCode(), request);
 					}
 				}
 				return bodyPublisher;
@@ -477,6 +479,22 @@ private <T> Mono<T> drainBody(ClientResponse response, Throwable ex) {
 					.onErrorResume(ex2 -> Mono.empty()).thenReturn(ex);
 		}
 
+		@SuppressWarnings("unchecked")
+		private <T extends Publisher<?>> T insertCheckpoint(T result, HttpStatus status, HttpRequest request) {
+			String httpMethod = request.getMethodValue();
+			URI uri = request.getURI();
+			String description = status + " from " + httpMethod + " " + uri + " [DefaultWebClient]";
+			if (result instanceof Mono) {
+				return (T) ((Mono<?>) result).checkpoint(description);
+			}
+			else if (result instanceof Flux) {
+				return (T) ((Flux<?>) result).checkpoint(description);
+			}
+			else {
+				return result;
+			}
+		}
+
 		private static Mono<WebClientResponseException> createResponseException(
 				ClientResponse response, HttpRequest request) {
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ExchangeFunctions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -105,7 +105,8 @@ public Mono<ClientResponse> exchange(ClientRequest clientRequest) {
 					.doOnCancel(() -> logger.debug(logPrefix + "Cancel signal (to close connection)"))
 					.map(httpResponse -> {
 						logResponse(httpResponse, logPrefix);
-						return new DefaultClientResponse(httpResponse, this.strategies, logPrefix);
+						return new DefaultClientResponse(
+								httpResponse, this.strategies, logPrefix, httpMethod.name() + " " + url);
 					});
 		}
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClientResponseException.java

@@ -63,11 +63,16 @@ public WebClientResponseException(int statusCode, String statusText,
 	 * Constructor with response data only, and a default message.
 	 * @since 5.1.4
 	 */
-	public WebClientResponseException(int statusCode, String statusText,
+	public WebClientResponseException(int status, String reasonPhrase,
 			@Nullable HttpHeaders headers, @Nullable byte[] body, @Nullable Charset charset,
 			@Nullable HttpRequest request) {
 
-		this(statusCode + " " + statusText, statusCode, statusText, headers, body, charset, request);
+		this(initMessage(status, reasonPhrase, request), status, reasonPhrase, headers, body, charset, request);
+	}
+
+	private static String initMessage(int status, String reasonPhrase, @Nullable HttpRequest request) {
+		return status + " " + reasonPhrase +
+				(request != null ? " from " + request.getMethodValue() + " " + request.getURI() : "");
 	}
 
 	/**