springcloud ribbon retryTemplate操作流程分析

一、在配置中加入

<dependency><groupId>org.springframework.retry</groupId><artifactId>spring-retry</artifactId>
</dependency>

二、初始化流程分析

1.构建LoadBalancedRetryFactory，在RibbonAutoConfiguration配置类中。

2.在LoadBalancerAutoConfiguration中构建LoadBalancerRequestFactory负载均衡请求工厂，以及RetryLoadBalancerInterceptor，并设置在RestTemplate中。

。

三、调用流程分析

1.还是进入RestTemplate.execute方法，

这里的request还是 InterceptingClientHttpRequest

2.进入拦截器调用，这里的拦截器为 RetryLoadBalancerInterceptor

3.RetryTemplate的interrupt方法，这里先创建一个重试策略，就是判断当前是否可重试。

package org.springframework.cloud.client.loadbalancer;/*** @author Ryan Baxter* @author Will Tran* @author Gang Li*/
public class RetryLoadBalancerInterceptor implements ClientHttpRequestInterceptor {@Overridepublic ClientHttpResponse intercept(final HttpRequest request, final byte[] body,final ClientHttpRequestExecution execution) throws IOException {final URI originalUri = request.getURI();final String serviceName = originalUri.getHost();Assert.state(serviceName != null, "Request URI does not contain a valid hostname: " + originalUri);final LoadBalancedRetryPolicy retryPolicy = lbRetryFactory.createRetryPolicy(serviceName,loadBalancer);RetryTemplate template = createRetryTemplate(serviceName, request, retryPolicy);return template.execute(context -> {ServiceInstance serviceInstance = null;if (context instanceof LoadBalancedRetryContext) {LoadBalancedRetryContext lbContext = (LoadBalancedRetryContext) context;serviceInstance = lbContext.getServiceInstance();}if (serviceInstance == null) {serviceInstance = loadBalancer.choose(serviceName);}ClientHttpResponse response = RetryLoadBalancerInterceptor.this.loadBalancer.execute(serviceName, serviceInstance,requestFactory.createRequest(request, body, execution));int statusCode = response.getRawStatusCode();if (retryPolicy != null && retryPolicy.retryableStatusCode(statusCode)) {byte[] bodyCopy = StreamUtils.copyToByteArray(response.getBody());response.close();throw new ClientHttpResponseStatusCodeException(serviceName, response, bodyCopy);}return response;}, new LoadBalancedRecoveryCallback<ClientHttpResponse, ClientHttpResponse>() {//This is a special case, where both parameters to LoadBalancedRecoveryCallback are//the same.  In most cases they would be different.@Overrideprotected ClientHttpResponse createResponse(ClientHttpResponse response, URI uri) {return response;}});}

4.首先创建RetryTemplate,这里面主要绑定InterceptorRetryPolicy拦截器重试策略。

5.拦截器重试策略包含了RibbonLoadBalacedRetryPolicy和一个服务实例选择器。RibbonLoadBalancerClient.

6.接着真正执行RetryTemplate.execute方法。一个重试回调，一个恢复回调。

@Override
public final <T, E extends Throwable> T execute(RetryCallback<T, E> retryCallback,RecoveryCallback<T> recoveryCallback) throws E {return doExecute(retryCallback, recoveryCallback, null);
}

7.RetryTemplate的doExecute方法，首先判断是否可重试，可以就调用retryCallback.doWithRetry(context),

org.springframework.retry.support.RetryTemplateprotected <T, E extends Throwable> T doExecute(RetryCallback<T, E> retryCallback,RecoveryCallback<T> recoveryCallback, RetryState state)throws E, ExhaustedRetryException {RetryPolicy retryPolicy = this.retryPolicy;BackOffPolicy backOffPolicy = this.backOffPolicy;// Allow the retry policy to initialise itself...RetryContext context = open(retryPolicy, state);RetrySynchronizationManager.register(context);Throwable lastException = null;boolean exhausted = false;try {// Give clients a chance to enhance the context...boolean running = doOpenInterceptors(retryCallback, context);while (canRetry(retryPolicy, context) && !context.isExhaustedOnly()) {try {lastException = null;return retryCallback.doWithRetry(context);}catch (Throwable e) {lastException = e;try {registerThrowable(retryPolicy, state, context, e);}catch (Exception ex) {throw new TerminatedRetryException("Could not register throwable",ex);}finally {doOnErrorInterceptors(retryCallback, context, e);}if (canRetry(retryPolicy, context) && !context.isExhaustedOnly()) {try {backOffPolicy.backOff(backOffContext);}catch (BackOffInterruptedException ex) {throw ex;}}if (this.logger.isDebugEnabled()) {this.logger.debug("Checking for rethrow: count=" + context.getRetryCount());}if (shouldRethrow(retryPolicy, context, state)) {if (this.logger.isDebugEnabled()) {this.logger.debug("Rethrow in retry for policy: count="+ context.getRetryCount());}throw RetryTemplate.<E>wrapIfNecessary(e);}}}exhausted = true;return handleRetryExhausted(recoveryCallback, context, state);}catch (Throwable e) {throw RetryTemplate.<E>wrapIfNecessary(e);}finally {close(retryPolicy, context, state, lastException == null || exhausted);doCloseInterceptors(retryCallback, context, lastException);RetrySynchronizationManager.clear();}}

8.这里首先为当前请求创建RetryContext，实现类为LoadBalancedRetryContext

9.判断是否可以重试接口，判断重试次数是否为0。

10.接着调用重试函数，又回到RetryLoadBalancerInterceptor。

11.这里的LoadBalancer为RibbonLoadBalanceClient,并且requestFactory.createRequest为之前未重试时普通的HTTP请求类。

ClientHttpResponse response = RetryLoadBalancerInterceptor.this.loadBalancer.execute(serviceName, serviceInstance,requestFactory.createRequest(request, body, execution));

12.LoadBalancerRequestFactory.createRequest又跳到InterceptingRequestExecution这个责任链执行器中。

13.由于这种普通的REQUEST,没有拦截器，直接调用HTTP请求对象替换实例URL中为真实服务实例域名，然后执行HTTP请求。

14.请求接口超时，被RetryTemplate.doExecute方法捕获异常，然后继续获取下一个实例重试。

这里对retryCnt加1.

下面重新选择一个实例，进行设置到context

接着又判断是否可重试。

然后尝试下一个节点，重新调用retryCallback函数。

重新请求成功。

拦截器执行完毕，返回成功。注意这个重试拦截器没有调用execution.interrupt，所以不会再执行责任链的下一个HANDLER.

最后处理结果，进行数据转换，返回数据。

返回结果完毕。

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