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TraceWebClientBeanPostProcessor.java
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TraceWebClientBeanPostProcessor.java
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/*
* Copyright 2013-2021 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.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.cloud.sleuth.instrument.web.client;
import java.util.List;
import java.util.concurrent.CancellationException;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
import java.util.function.Function;
import brave.Span;
import brave.http.HttpClientHandler;
import brave.http.HttpClientRequest;
import brave.http.HttpClientResponse;
import brave.http.HttpTracing;
import brave.propagation.CurrentTraceContext;
import brave.propagation.CurrentTraceContext.Scope;
import brave.propagation.TraceContext;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.publisher.Mono;
import reactor.util.annotation.Nullable;
import reactor.util.context.Context;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.cloud.sleuth.internal.LazyBean;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.web.reactive.function.client.ClientRequest;
import org.springframework.web.reactive.function.client.ClientResponse;
import org.springframework.web.reactive.function.client.ExchangeFilterFunction;
import org.springframework.web.reactive.function.client.ExchangeFunction;
import org.springframework.web.reactive.function.client.WebClient;
import static org.springframework.cloud.sleuth.instrument.reactor.ReactorSleuth.scopePassingSpanOperator;
/**
* {@link BeanPostProcessor} to wrap a {@link WebClient} instance into its trace
* representation.
*
* @author Marcin Grzejszczak
* @since 2.0.0
*/
final class TraceWebClientBeanPostProcessor implements BeanPostProcessor {
final ConfigurableApplicationContext springContext;
TraceWebClientBeanPostProcessor(ConfigurableApplicationContext springContext) {
this.springContext = springContext;
}
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) {
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) {
if (bean instanceof WebClient) {
WebClient webClient = (WebClient) bean;
return wrapBuilder(webClient.mutate()).build();
}
else if (bean instanceof WebClient.Builder) {
WebClient.Builder webClientBuilder = (WebClient.Builder) bean;
return wrapBuilder(webClientBuilder);
}
return bean;
}
private WebClient.Builder wrapBuilder(WebClient.Builder webClientBuilder) {
return webClientBuilder.filters(addTraceExchangeFilterFunctionIfNotPresent());
}
private Consumer<List<ExchangeFilterFunction>> addTraceExchangeFilterFunctionIfNotPresent() {
return functions -> {
boolean noneMatch = noneMatchTraceExchangeFunction(functions);
if (noneMatch) {
functions.add(new TraceExchangeFilterFunction(this.springContext));
}
};
}
private boolean noneMatchTraceExchangeFunction(
List<ExchangeFilterFunction> functions) {
for (ExchangeFilterFunction function : functions) {
if (function instanceof TraceExchangeFilterFunction) {
return false;
}
}
return true;
}
}
final class TraceExchangeFilterFunction implements ExchangeFilterFunction {
private static final Log log = LogFactory.getLog(TraceExchangeFilterFunction.class);
final LazyBean<HttpTracing> httpTracing;
final Function<? super Publisher<DataBuffer>, ? extends Publisher<DataBuffer>> scopePassingTransformer;
// Lazy initialized fields
HttpClientHandler<HttpClientRequest, HttpClientResponse> handler;
CurrentTraceContext currentTraceContext;
TraceExchangeFilterFunction(ConfigurableApplicationContext springContext) {
this.httpTracing = LazyBean.create(springContext, HttpTracing.class);
this.scopePassingTransformer = scopePassingSpanOperator(springContext);
}
public static ExchangeFilterFunction create(
ConfigurableApplicationContext springContext) {
return new TraceExchangeFilterFunction(springContext);
}
@Override
public Mono<ClientResponse> filter(ClientRequest request, ExchangeFunction next) {
return new MonoWebClientTrace(next, request, this);
}
CurrentTraceContext currentTraceContext() {
if (this.currentTraceContext == null) {
this.currentTraceContext = httpTracing.get().tracing().currentTraceContext();
}
return this.currentTraceContext;
}
HttpClientHandler<HttpClientRequest, HttpClientResponse> handler() {
if (this.handler == null) {
this.handler = HttpClientHandler.create(this.httpTracing.get());
}
return this.handler;
}
private static final class MonoWebClientTrace extends Mono<ClientResponse> {
final ExchangeFunction next;
final ClientRequest request;
final HttpClientHandler<HttpClientRequest, HttpClientResponse> handler;
final CurrentTraceContext currentTraceContext;
final Function<? super Publisher<DataBuffer>, ? extends Publisher<DataBuffer>> scopePassingTransformer;
@Nullable
final TraceContext parent;
MonoWebClientTrace(ExchangeFunction next, ClientRequest request,
TraceExchangeFilterFunction filterFunction) {
this.next = next;
this.request = request;
this.handler = filterFunction.handler();
this.currentTraceContext = filterFunction.currentTraceContext();
this.scopePassingTransformer = filterFunction.scopePassingTransformer;
this.parent = currentTraceContext.get();
}
@Override
public void subscribe(CoreSubscriber<? super ClientResponse> subscriber) {
Context context = subscriber.currentContext();
ClientRequestWrapper wrapper = new ClientRequestWrapper(request);
Span span = handler.handleSendWithParent(wrapper, parent);
if (log.isDebugEnabled()) {
log.debug("HttpClientHandler::handleSend: " + span);
}
// NOTE: We are starting the client span for the request here, but it could be
// canceled prior to actually being invoked. TraceWebClientSubscription will
// abandon this span, if cancel() happens before request().
this.next.exchange(wrapper.buildRequest()).subscribe(
new TraceWebClientSubscriber(subscriber, context, span, this));
}
}
static final class TraceWebClientSubscriber extends AtomicReference<Span>
implements CoreSubscriber<ClientResponse> {
final CoreSubscriber<? super ClientResponse> actual;
final Context context;
@Nullable
final TraceContext parent;
final HttpClientHandler<HttpClientRequest, HttpClientResponse> handler;
final Function<? super Publisher<DataBuffer>, ? extends Publisher<DataBuffer>> scopePassingTransformer;
final CurrentTraceContext currentTraceContext;
TraceWebClientSubscriber(CoreSubscriber<? super ClientResponse> actual,
Context ctx, Span clientSpan, MonoWebClientTrace mono) {
this.actual = actual;
this.parent = mono.parent;
this.handler = mono.handler;
this.currentTraceContext = mono.currentTraceContext;
this.scopePassingTransformer = mono.scopePassingTransformer;
this.context = parent != null
&& !parent.equals(ctx.getOrDefault(TraceContext.class, null))
? ctx.put(TraceContext.class, parent) : ctx;
set(clientSpan);
}
@Override
public void onSubscribe(Subscription subscription) {
this.actual.onSubscribe(new TraceWebClientSubscription(subscription, this));
}
@Override
public void onNext(ClientResponse response) {
try (Scope scope = currentTraceContext.maybeScope(parent)) {
// decorate response body
this.actual
.onNext(ClientResponse.from(response)
.body(response.bodyToFlux(DataBuffer.class)
.transform(this.scopePassingTransformer))
.build());
}
finally {
Span span = getAndSet(null);
if (span != null) {
// TODO: is there a way to read the request at response time?
this.handler.handleReceive(new ClientResponseWrapper(response), null,
span);
}
}
}
@Override
public void onError(Throwable t) {
try (Scope scope = currentTraceContext.maybeScope(parent)) {
this.actual.onError(t);
}
finally {
Span span = getAndSet(null);
if (span != null) {
span.error(t);
span.finish();
}
}
}
@Override
public void onComplete() {
try (Scope scope = currentTraceContext.maybeScope(parent)) {
this.actual.onComplete();
}
finally {
Span span = getAndSet(null);
if (span != null) {
// TODO: backfill empty test:
// https://github.com/spring-cloud/spring-cloud-sleuth/issues/1570
if (log.isDebugEnabled()) {
log.debug("Reached OnComplete without finishing [" + span + "]");
}
span.abandon();
}
}
}
@Override
public Context currentContext() {
return this.context;
}
}
static class TraceWebClientSubscription implements Subscription {
static final Exception CANCELLED_ERROR = new CancellationException("CANCELLED") {
@Override
public Throwable fillInStackTrace() {
return this; // stack trace doesn't add value here
}
};
final AtomicReference<Span> pendingSpan;
final Subscription delegate;
volatile boolean requested;
TraceWebClientSubscription(Subscription delegate,
AtomicReference<Span> pendingSpan) {
this.delegate = delegate;
this.pendingSpan = pendingSpan;
}
@Override
public void request(long n) {
requested = true;
delegate.request(n); // Not scoping to save overhead
}
@Override
public void cancel() {
delegate.cancel(); // Not scoping to save overhead
// Check to see if Subscription.cancel() happened after request(),
// but before another signal (like onComplete) completed the span.
Span span = pendingSpan.getAndSet(null);
if (span != null) {
if (log.isDebugEnabled()) {
log.debug(
"Subscription was cancelled. TraceWebClientBeanPostProcessor Will close the span ["
+ span + "]");
}
if (!requested) { // Abandon the span.
span.abandon();
}
else { // Request was canceled in-flight
span.error(CANCELLED_ERROR);
span.finish();
}
}
}
}
private static final class ClientRequestWrapper extends HttpClientRequest {
final ClientRequest delegate;
final ClientRequest.Builder builder;
ClientRequestWrapper(ClientRequest delegate) {
this.delegate = delegate;
this.builder = ClientRequest.from(delegate);
}
@Override
public Object unwrap() {
return delegate;
}
@Override
public String method() {
return delegate.method().name();
}
@Override
public String path() {
return delegate.url().getPath();
}
@Override
public String url() {
return delegate.url().toString();
}
@Override
public String header(String name) {
return delegate.headers().getFirst(name);
}
@Override
public void header(String name, String value) {
builder.header(name, value);
}
ClientRequest buildRequest() {
return builder.build();
}
}
static final class ClientResponseWrapper extends HttpClientResponse {
final ClientResponse delegate;
ClientResponseWrapper(ClientResponse delegate) {
this.delegate = delegate;
}
@Override
public Object unwrap() {
return delegate;
}
@Override
public int statusCode() {
// unlike statusCode(), this doesn't throw
return Math.max(delegate.rawStatusCode(), 0);
}
}
}