本系列代码地址： https://github.com/JoJoTec/spring-cloud-parent
要想实现我们上一节中提到的：
- 需要在重试以及断路中加一些日志，便于日后的优化
- 需要定义重试的 Exception，并且与断路器相结合，将非 2xx 的响应码也封装成特定的异常
- 需要在断路器相关的 Operator 中增加类似于 FeignClient 中的负载均衡的数据更新，使得负载均衡更加智能
我们需要将 resilience4j 本身提供的粘合库做一些改造，其实主要就是对 resilience4j 实现的 project reactor 的 Operator 进行改造。
关于断路器的改造
首先，WebClient 的返回对象只可能是 ClientResponse 类型，所以我们这里改造出来的 Operator 不必带上形参，只需要针对 ClientResponse 即可，即：
public class ClientResponseCircuitBreakerOperator implements UnaryOperator<Publisher<ClientResponse>> { ... }
在原有的断路器逻辑中，我们需要加入针对 GET 方法以及之前定义的可以重试的路径匹配配置可以重试的逻辑，这需要我们拿到原有请求的 URL 信息。但是 ClientResponse 中并没有暴露这些信息的接口，其默认实现 DefaultClientResponse（我们只要没有自己给 WebClient 加入特殊的改造逻辑，实现都是 DefaultClientResponse） 中的 request() 方法可以获取请求 HttpRequest，其中包含 url 信息。但是这个类还有方法都是 package-private 的，我们需要反射出来：
ClientResponseCircuitBreakerSubscriber
private static final Class<?> aClass; private static final Method request; static { try { aClass = Class.forName("org.springframework.web.reactive.function.client.DefaultClientResponse"); request = ReflectionUtils.findMethod(aClass, "request"); request.setAccessible(true); } catch (Exception e) { throw new RuntimeException(e); } }
之后，在获取到 ClientResponse 之后记录断路器的逻辑中，需要加入上面提到的关于重试的改造，以及负载均衡器的记录：
ClientResponseCircuitBreakerSubscriber
protected void hookOnNext(ClientResponse clientResponse) { if (!isDisposed()) { if (singleProducer && successSignaled.compareAndSet(false, true)) { int rawStatusCode = clientResponse.rawStatusCode(); HttpStatus httpStatus = HttpStatus.resolve(rawStatusCode); try { HttpRequest httpRequest = (HttpRequest) request.invoke(clientResponse); //判断方法是否为 GET，以及是否在可重试路径配置中，从而得出是否可以重试 if (httpRequest.getMethod() != HttpMethod.GET && !webClientProperties.retryablePathsMatch(httpRequest.getURI().getPath())) { //如果不能重试，则直接返回结果 circuitBreaker.onResult(circuitBreaker.getCurrentTimestamp() - start, circuitBreaker.getTimestampUnit(), clientResponse); } else { if (httpStatus != null && httpStatus.is2xxSuccessful()) { //如果成功，则直接返回结果 circuitBreaker.onResult(circuitBreaker.getCurrentTimestamp() - start, circuitBreaker.getTimestampUnit(), clientResponse); } else { /** * 如果异常，参考 DefaultClientResponse 的代码进行异常封装 * @see org.springframework.web.reactive.function.client.DefaultClientResponse#createException */ Exception exception; if (httpStatus != null) { exception = WebClientResponseException.create(rawStatusCode, httpStatus.getReasonPhrase(), clientResponse.headers().asHttpHeaders(), EMPTY, null, null); } else { exception = new UnknownHttpStatusCodeException(rawStatusCode, clientResponse.headers().asHttpHeaders(), EMPTY, null, null); } circuitBreaker.onError(circuitBreaker.getCurrentTimestamp() - start, circuitBreaker.getTimestampUnit(), exception); downstreamSubscriber.onError(exception); return; } } } catch (Exception e) { log.fatal("judge request method in circuit breaker error! the resilience4j feature would not be enabled: {}", e.getMessage(), e); circuitBreaker.onResult(circuitBreaker.getCurrentTimestamp() - start, circuitBreaker.getTimestampUnit(), clientResponse); } } eventWasEmitted.set(true); downstreamSubscriber.onNext(clientResponse); } }
同样的，在原有的完成，取消还有失败的记录逻辑中，也加上记录负载均衡数据：
ClientResponseCircuitBreakerSubscriber
@Override protected void hookOnComplete() { if (successSignaled.compareAndSet(false, true)) { serviceInstanceMetrics.recordServiceInstanceCalled(serviceInstance, true); circuitBreaker.onSuccess(circuitBreaker.getCurrentTimestamp() - start, circuitBreaker.getTimestampUnit()); } downstreamSubscriber.onComplete(); } @Override public void hookOnCancel() { if (!successSignaled.get()) { serviceInstanceMetrics.recordServiceInstanceCalled(serviceInstance, true); if (eventWasEmitted.get()) { circuitBreaker.onSuccess(circuitBreaker.getCurrentTimestamp() - start, circuitBreaker.getTimestampUnit()); } else { circuitBreaker.releasePermission(); } } } @Override protected void hookOnError(Throwable e) { serviceInstanceMetrics.recordServiceInstanceCalled(serviceInstance, false); circuitBreaker.onError(circuitBreaker.getCurrentTimestamp() - start, circuitBreaker.getTimestampUnit(), e); downstreamSubscriber.onError(e); }
粘合 WebClient 与 resilience4j 的同时覆盖重试逻辑
由于前面的断路器中，我们针对可以重试的非 2XX 响应封装成为 WebClientResponseException。所以在重试器中，我们需要加上针对这个异常的重试。
同时，需要将重试器放在负载均衡器之前，因为每次重试，都要从负载均衡器中获取一个新的实例。同时，断路器需要放在负载均衡器之后，因为只有在这个之后，才能获取到本次调用的实例，我们的的断路器是针对实例方法级别的：
WebClientDefaultConfiguration.java
@Bean public WebClient getWebClient( ReactorLoadBalancerExchangeFilterFunction lbFunction, WebClientConfigurationProperties webClientConfigurationProperties, Environment environment, RetryRegistry retryRegistry, CircuitBreakerRegistry circuitBreakerRegistry, ServiceInstanceMetrics serviceInstanceMetrics ) { String name = environment.getProperty(WebClientNamedContextFactory.PROPERTY_NAME); Map<String, WebClientConfigurationProperties.WebClientProperties> configs = webClientConfigurationProperties.getConfigs(); if (configs == null || configs.size() == 0) { throw new BeanCreationException("Failed to create webClient, please provide configurations under namespace: webclient.configs"); } WebClientConfigurationProperties.WebClientProperties webClientProperties = configs.get(name); if (webClientProperties == null) { throw new BeanCreationException("Failed to create webClient, please provide configurations under namespace: webclient.configs." + name); } String serviceName = webClientProperties.getServiceName(); //如果没填写微服务名称，就使用配置 key 作为微服务名称 if (StringUtils.isBlank(serviceName)) { serviceName = name; } String baseUrl = webClientProperties.getBaseUrl(); //如果没填写 baseUrl，就使用微服务名称填充 if (StringUtils.isBlank(baseUrl)) { baseUrl = "http://" + serviceName; } Retry retry = null; try { retry = retryRegistry.retry(serviceName, serviceName); } catch (ConfigurationNotFoundException e) { retry = retryRegistry.retry(serviceName); } //覆盖其中的异常判断 retry = Retry.of(serviceName, RetryConfig.from(retry.getRetryConfig()).retryOnException(throwable -> { //WebClientResponseException 会重试，因为在这里能 catch 的 WebClientResponseException 只对可以重试的请求封装了 WebClientResponseException //参考 ClientResponseCircuitBreakerSubscriber 的代码 if (throwable instanceof WebClientResponseException) { log.info("should retry on {}", throwable.toString()); return true; } //断路器异常重试，因为请求没有发出去 if (throwable instanceof CallNotPermittedException) { log.info("should retry on {}", throwable.toString()); return true; } if (throwable instanceof WebClientRequestException) { WebClientRequestException webClientRequestException = (WebClientRequestException) throwable; HttpMethod method = webClientRequestException.getMethod(); URI uri = webClientRequestException.getUri(); //判断是否为响应超时，响应超时代表请求已经发出去了，对于非 GET 并且没有标注可以重试的请求则不能重试 boolean isResponseTimeout = false; Throwable cause = throwable.getCause(); //netty 的读取超时一般是 ReadTimeoutException if (cause instanceof ReadTimeoutException) { log.info("Cause is a ReadTimeoutException which indicates it is a response time out"); isResponseTimeout = true; } else { //对于其他一些框架，使用了 java 底层 nio 的一般是 SocketTimeoutException，message 为 read time out //还有一些其他异常，但是 message 都会有 read time out 字段，所以通过 message 判断 String message = throwable.getMessage(); if (StringUtils.isNotBlank(message) && StringUtils.containsIgnoreCase(message.replace(" ", ""), "readtimeout")) { log.info("Throwable message contains readtimeout which indicates it is a response time out"); isResponseTimeout = true; } } //如果请求是 GET 或者标注了重试，则直接判断可以重试 if (method == HttpMethod.GET || webClientProperties.retryablePathsMatch(uri.getPath())) { log.info("should retry on {}-{}, {}", method, uri, throwable.toString()); return true; } else { //否则，只针对请求还没有发出去的异常进行重试 if (isResponseTimeout) { log.info("should not retry on {}-{}, {}", method, uri, throwable.toString()); } else { log.info("should retry on {}-{}, {}", method, uri, throwable.toString()); return true; } } } return false; }).build()); HttpClient httpClient = HttpClient .create() .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, (int) webClientProperties.getConnectTimeout().toMillis()) .doOnConnected(connection -> connection .addHandlerLast(new ReadTimeoutHandler((int) webClientProperties.getResponseTimeout().toSeconds())) .addHandlerLast(new WriteTimeoutHandler((int) webClientProperties.getResponseTimeout().toSeconds())) ); Retry finalRetry = retry; String finalServiceName = serviceName; return WebClient.builder() .exchangeStrategies(ExchangeStrategies.builder() .codecs(configurer -> configurer .defaultCodecs() //最大 body 占用 16m 内存 .maxInMemorySize(16 * 1024 * 1024)) .build()) .clientConnector(new ReactorClientHttpConnector(httpClient)) //Retry在负载均衡前 .filter((clientRequest, exchangeFunction) -> { return exchangeFunction .exchange(clientRequest) .transform(ClientResponseRetryOperator.of(finalRetry)); }) //负载均衡器，改写url .filter(lbFunction) //实例级别的断路器需要在负载均衡获取真正地址之后 .filter((clientRequest, exchangeFunction) -> { ServiceInstance serviceInstance = getServiceInstance(clientRequest); serviceInstanceMetrics.recordServiceInstanceCall(serviceInstance); CircuitBreaker circuitBreaker; //这时候的url是经过负载均衡器的，是实例的url //需要注意的一点是，使用异步 client 的时候，最好不要带路径参数，否则这里的断路器效果不好 //断路器是每个实例每个路径一个断路器 String instancId = clientRequest.url().getHost() + ":" + clientRequest.url().getPort() + clientRequest.url().getPath(); try { //使用实例id新建或者获取现有的CircuitBreaker,使用serviceName获取配置 circuitBreaker = circuitBreakerRegistry.circuitBreaker(instancId, finalServiceName); } catch (ConfigurationNotFoundException e) { circuitBreaker = circuitBreakerRegistry.circuitBreaker(instancId); } log.info("webclient circuit breaker [{}-{}] status: {}, data: {}", finalServiceName, instancId, circuitBreaker.getState(), JSON.toJSONString(circuitBreaker.getMetrics())); return exchangeFunction.exchange(clientRequest).transform(ClientResponseCircuitBreakerOperator.of(circuitBreaker, serviceInstance, serviceInstanceMetrics, webClientProperties)); }).baseUrl(baseUrl) .build(); } private ServiceInstance getServiceInstance(ClientRequest clientRequest) { URI url = clientRequest.url(); DefaultServiceInstance defaultServiceInstance = new DefaultServiceInstance(); defaultServiceInstance.setHost(url.getHost()); defaultServiceInstance.setPort(url.getPort()); return defaultServiceInstance; }
这样，我们就实现了我们封装的基于配置的 WebClient
