這篇文章給大家介紹Spring Cloud 超時和重試機制是什么，內(nèi)容非常詳細(xì)，感興趣的小伙伴們可以參考借鑒，希望對大家能有所幫助。
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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默認(rèn)關(guān)閉了Feign的重試機制
重慶分公司
重慶分公司
//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;
}
};如果想要開啟的話，就自己聲明一個bean
@Bean
public Retryer feignRetryer() {
return new Retryer.Default();
}#ribbon的超時時間 #如果ribbon和feign的超時時間都配置了，ribbon的配置會被覆蓋 ribbon: ReadTimeout: 3000 ConnectTimeout: 3000
ribbon: MaxAutoRetries: 1 #同一臺實例最大重試次數(shù),不包括首次調(diào)用 MaxAutoRetriesNextServer: 1 #重試負(fù)載均衡其他的實例最大重試次數(shù),不包括首次調(diào)用 OkToRetryOnAllOperations: false #是否所有操作都重試
hystrix: command: default: execution: timeout: enabled: true isolation: thread: timeoutInMilliseconds: 1000
注意Hystrix的超時時間要超過ribbon的重試時間，否則ribbon重試過程中，就會先觸發(fā)Hystrix的熔斷
超時時間計算可以參考zuul中的AbstractRibbonCommand類的getRibbonTimeout()方法，
protected static int getRibbonTimeout(IClientConfig config, String commandKey) {
int ribbonTimeout;
// 這是比較異常的情況，不說
if (config == null) {
ribbonTimeout = RibbonClientConfiguration.DEFAULT_READ_TIMEOUT + RibbonClientConfiguration.DEFAULT_CONNECT_TIMEOUT;
} else {
// 這里獲取了四個參數(shù)，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的計算方法在這里，以上文的設(shè)置為例
// ribbonTimeout = (3000 + 3000) * (1 + 1) * (1 + 1) = 24000(毫秒)
ribbonTimeout = (ribbonReadTimeout + ribbonConnectTimeout) * (maxAutoRetries + 1) * (maxAutoRetriesNextServer + 1);
}
return ribbonTimeout;
}RestTemplate默認(rèn)超時時間是-1，即不會超時，如果想要設(shè)置的話，可以這么做
@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的子類
@Override
public RequestSpecificRetryHandler getRequestSpecificRetryHandler(
RibbonRequest request, IClientConfig requestConfig) {
//如果isOkToRetryOnAllOperations參數(shù)為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：只對連接錯誤發(fā)起重試
* okToRetryOnAllErrors：對于所有錯誤都會發(fā)起重試
*/
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);
}
}
} 可以看到如果設(shè)置了isOkToRetryOnAllOperations為true，就會對所有錯誤發(fā)起重試，否則的話就只對連接異常發(fā)起重試，判斷是否重試的代碼如下：
//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);
}
}這里會有一個問題，如果你是新增/修改操作，系統(tǒng)處理時間過長導(dǎo)致超時，也會觸發(fā)Feign的自動重試，如果你的冪等性做的不好，就會導(dǎo)致很嚴(yán)重的后果。
而如果是連接異常，此時請求還沒有發(fā)送過去，所以是不會重復(fù)執(zhí)行的。
當(dāng)然了，在分布式系統(tǒng)中，還是建議做好每個接口的冪等性。
//SynchronousMethodHandler.java
@Override
public Object invoke(Object[] argv) throws Throwable {
RequestTemplate template = buildTemplateFromArgs.create(argv);
//這里我們假設(shè)你開啟了Feign的重試，并且使用的是Retryer.Default這個類
Retryer retryer = this.retryer.clone();
while (true) {
try {
//這里會調(diào)用到5.3節(jié)executeWithLoadBalancer()方法
return executeAndDecode(template);
} catch (RetryableException e) {
try {
//在重試次數(shù)之內(nèi)，會等待一段時間返回，繼續(xù)while循環(huán)，否則會拋出異常跳出循環(huán)
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);
}
}
} 上邊是調(diào)用的入口，下邊是重試執(zhí)行的邏輯，由于的RxJava寫的，暫時看不懂，先貼出來日后再說......
