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这篇文章给大家介绍Spring Cloud 超时和重试机制是什么，内容非常详细，感兴趣的小伙伴们可以参考借鉴，希望对大家能有所帮助。
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本文基于Spring Cloud Greenwich.SR2、Spring Boot 2.1.6.RELEASE
feign: client: config: default: connect-timeout: 2000 read-timeout: 2000
Spring Cloud默认关闭了Feign的重试机制
//org.springframework.cloud.openfeign.FeignClientsConfiguration
@Bean
@ConditionalOnMissingBean
public Retryer feignRetryer() {
return Retryer.NEVER_RETRY;
}
//feign.Retryer
/**
* Implementation that never retries request. It propagates the RetryableException.
*/
Retryer NEVER_RETRY = new Retryer() {
@Override
public void continueOrPropagate(RetryableException e) {
throw e;
}
@Override
public Retryer clone() {
return this;
}
};如果想要开启的话，就自己声明一个bean
@Bean
public Retryer feignRetryer() {
return new Retryer.Default();
}#ribbon的超时时间 #如果ribbon和feign的超时时间都配置了，ribbon的配置会被覆盖 ribbon: ReadTimeout: 3000 ConnectTimeout: 3000
ribbon: MaxAutoRetries: 1 #同一台实例最大重试次数,不包括首次调用 MaxAutoRetriesNextServer: 1 #重试负载均衡其他的实例最大重试次数,不包括首次调用 OkToRetryOnAllOperations: false #是否所有操作都重试
hystrix: command: default: execution: timeout: enabled: true isolation: thread: timeoutInMilliseconds: 1000
注意Hystrix的超时时间要超过ribbon的重试时间，否则ribbon重试过程中，就会先触发Hystrix的熔断
超时时间计算可以参考zuul中的AbstractRibbonCommand类的getRibbonTimeout()方法，
protected static int getRibbonTimeout(IClientConfig config, String commandKey) {
int ribbonTimeout;
// 这是比较异常的情况，不说
if (config == null) {
ribbonTimeout = RibbonClientConfiguration.DEFAULT_READ_TIMEOUT + RibbonClientConfiguration.DEFAULT_CONNECT_TIMEOUT;
} else {
// 这里获取了四个参数，ReadTimeout，ConnectTimeout，MaxAutoRetries， MaxAutoRetriesNextServer
int ribbonReadTimeout = getTimeout(config, commandKey, "ReadTimeout",
IClientConfigKey.Keys.ReadTimeout, RibbonClientConfiguration.DEFAULT_READ_TIMEOUT);
int ribbonConnectTimeout = getTimeout(config, commandKey, "ConnectTimeout",
IClientConfigKey.Keys.ConnectTimeout, RibbonClientConfiguration.DEFAULT_CONNECT_TIMEOUT);
int maxAutoRetries = getTimeout(config, commandKey, "MaxAutoRetries",
IClientConfigKey.Keys.MaxAutoRetries, DefaultClientConfigImpl.DEFAULT_MAX_AUTO_RETRIES);
int maxAutoRetriesNextServer = getTimeout(config, commandKey, "MaxAutoRetriesNextServer",
IClientConfigKey.Keys.MaxAutoRetriesNextServer, DefaultClientConfigImpl.DEFAULT_MAX_AUTO_RETRIES_NEXT_SERVER);
// ribbonTimeout的计算方法在这里，以上文的设置为例
// ribbonTimeout = (3000 + 3000) * (1 + 1) * (1 + 1) = 24000(毫秒)
ribbonTimeout = (ribbonReadTimeout + ribbonConnectTimeout) * (maxAutoRetries + 1) * (maxAutoRetriesNextServer + 1);
}
return ribbonTimeout;
}RestTemplate默认超时时间是-1，即不会超时，如果想要设置的话，可以这么做
@Bean
@Primary
@LoadBalanced
public RestTemplate lbRestTemplate() {
SimpleClientHttpRequestFactory simpleClientHttpRequestFactory = new SimpleClientHttpRequestFactory();
simpleClientHttpRequestFactory.setConnectTimeout(1000);
simpleClientHttpRequestFactory.setReadTimeout(1000);
return new RestTemplate(simpleClientHttpRequestFactory);
}//AbstractLoadBalancerAwareClient.java
public T executeWithLoadBalancer(final S request, final IClientConfig requestConfig) throws ClientException {
LoadBalancerCommand command = buildLoadBalancerCommand(request, requestConfig);
//省略...
}
protected LoadBalancerCommand buildLoadBalancerCommand(final S request, final IClientConfig config) {
RequestSpecificRetryHandler handler = getRequestSpecificRetryHandler(request, config);
//省略...
}
//FeignLoadBalancer.java
//FeignLoadBalancer是AbstractLoadBalancerAwareClient的子类
@Override
public RequestSpecificRetryHandler getRequestSpecificRetryHandler(
RibbonRequest request, IClientConfig requestConfig) {
//如果isOkToRetryOnAllOperations参数为true
if (this.ribbon.isOkToRetryOnAllOperations()) {
return new RequestSpecificRetryHandler(true, true, this.getRetryHandler(), requestConfig);
}
if (!request.toRequest().httpMethod().name().equals("GET")) {
return new RequestSpecificRetryHandler(true, false, this.getRetryHandler(), requestConfig);
}
else {
return new RequestSpecificRetryHandler(true, true, this.getRetryHandler(), requestConfig);
}
}
//RequestSpecificRetryHandler.java
/**
* okToRetryOnConnectErrors：只对连接错误发起重试
* okToRetryOnAllErrors：对于所有错误都会发起重试
*/
public RequestSpecificRetryHandler(boolean okToRetryOnConnectErrors, boolean okToRetryOnAllErrors, RetryHandler baseRetryHandler, @Nullable IClientConfig requestConfig) {
Preconditions.checkNotNull(baseRetryHandler);
this.okToRetryOnConnectErrors = okToRetryOnConnectErrors;
this.okToRetryOnAllErrors = okToRetryOnAllErrors;
this.fallback = baseRetryHandler;
if (requestConfig != null) {
if (requestConfig.containsProperty(CommonClientConfigKey.MaxAutoRetries)) {
retrySameServer = requestConfig.get(CommonClientConfigKey.MaxAutoRetries);
}
if (requestConfig.containsProperty(CommonClientConfigKey.MaxAutoRetriesNextServer)) {
retryNextServer = requestConfig.get(CommonClientConfigKey.MaxAutoRetriesNextServer);
}
}
} 可以看到如果设置了isOkToRetryOnAllOperations为true，就会对所有错误发起重试，否则的话就只对连接异常发起重试，判断是否重试的代码如下：
//RequestSpecificRetryHandler.java
@Override
public boolean isRetriableException(Throwable e, boolean sameServer) {
if (okToRetryOnAllErrors) {
return true;
}
else if (e instanceof ClientException) {
ClientException ce = (ClientException) e;
if (ce.getErrorType() == ClientException.ErrorType.SERVER_THROTTLED) {
return !sameServer;
} else {
return false;
}
}
else {
return okToRetryOnConnectErrors && isConnectionException(e);
}
}这里会有一个问题，如果你是新增/修改操作，系统处理时间过长导致超时，也会触发Feign的自动重试，如果你的幂等性做的不好，就会导致很严重的后果。
而如果是连接异常，此时请求还没有发送过去，所以是不会重复执行的。
当然了，在分布式系统中，还是建议做好每个接口的幂等性。
//SynchronousMethodHandler.java
@Override
public Object invoke(Object[] argv) throws Throwable {
RequestTemplate template = buildTemplateFromArgs.create(argv);
//这里我们假设你开启了Feign的重试，并且使用的是Retryer.Default这个类
Retryer retryer = this.retryer.clone();
while (true) {
try {
//这里会调用到5.3节executeWithLoadBalancer()方法
return executeAndDecode(template);
} catch (RetryableException e) {
try {
//在重试次数之内，会等待一段时间返回，继续while循环，否则会抛出异常跳出循环
retryer.continueOrPropagate(e);
} catch (RetryableException th) {
Throwable cause = th.getCause();
if (propagationPolicy == UNWRAP && cause != null) {
throw cause;
} else {
throw th;
}
}
if (logLevel != Logger.Level.NONE) {
logger.logRetry(metadata.configKey(), logLevel);
}
continue;
}
}
}//AbstractLoadBalancerAwareClient.java
public T executeWithLoadBalancer(final S request, final IClientConfig requestConfig) throws ClientException {
LoadBalancerCommand command = buildLoadBalancerCommand(request, requestConfig);
try {
return command.submit(
new ServerOperation() {
@Override
public Observable call(Server server) {
URI finalUri = reconstructURIWithServer(server, request.getUri());
S requestForServer = (S) request.replaceUri(finalUri);
try {
return Observable.just(AbstractLoadBalancerAwareClient.this.execute(requestForServer, requestConfig));
}
catch (Exception e) {
return Observable.error(e);
}
}
})
.toBlocking()
.single();
} catch (Exception e) {
Throwable t = e.getCause();
if (t instanceof ClientException) {
throw (ClientException) t;
} else {
throw new ClientException(e);
}
}
} 上边是调用的入口，下边是重试执行的逻辑，由于的RxJava写的，暂时看不懂，先贴出来日后再说......
