這篇文章主要為大家展示了“Spring Cloud請(qǐng)求重試機(jī)制的示例分析”，內(nèi)容簡(jiǎn)而易懂，條理清晰，希望能夠幫助大家解決疑惑，下面讓小編帶領(lǐng)大家一起研究并學(xué)習(xí)一下“Spring Cloud請(qǐng)求重試機(jī)制的示例分析”這篇文章吧。
讓客戶滿意是我們工作的目標(biāo)，不斷超越客戶的期望值來自于我們對(duì)這個(gè)行業(yè)的熱愛。我們立志把好的技術(shù)通過有效、簡(jiǎn)單的方式提供給客戶，將通過不懈努力成為客戶在信息化領(lǐng)域值得信任、有價(jià)值的長(zhǎng)期合作伙伴，公司提供的服務(wù)項(xiàng)目有：空間域名、虛擬空間、營(yíng)銷軟件、網(wǎng)站建設(shè)、靖邊網(wǎng)站維護(hù)、網(wǎng)站推廣。
場(chǎng)景
發(fā)布微服務(wù)的操作一般都是打完新代碼的包，kill掉在跑的應(yīng)用，替換新的包，啟動(dòng)。
spring cloud 中使用eureka為注冊(cè)中心，它是允許服務(wù)列表數(shù)據(jù)的延遲性的，就是說即使應(yīng)用已經(jīng)不在服務(wù)列表了，客戶端在一段時(shí)間內(nèi)依然會(huì)請(qǐng)求這個(gè)地址。那么就會(huì)出現(xiàn)請(qǐng)求正在發(fā)布的地址，而導(dǎo)致失敗。
我們會(huì)優(yōu)化服務(wù)列表的刷新時(shí)間，以提高服務(wù)列表信息的時(shí)效性。但是無論怎樣，都無法避免有那么一段時(shí)間是數(shù)據(jù)不一致的。
所以我們想到一個(gè)辦法就是重試機(jī)制，當(dāng)a機(jī)子在重啟時(shí)，同個(gè)集群的b是可以正常提供服務(wù)的，如果有重試機(jī)制就可以在上面這個(gè)場(chǎng)景里進(jìn)行重試到b而不影響正確響應(yīng)。
操作
需要進(jìn)行如下的操作：
ribbon:
ReadTimeout: 10000
ConnectTimeout: 10000
MaxAutoRetries: 0
MaxAutoRetriesNextServer: 1
OkToRetryOnAllOperations: false
引入spring-retry包
org.springframework.retry
spring-retry
以zuul為例子還需要配置開啟重試：
zuul.retryable=true
遇到了問題
然而萬事總沒那么一帆風(fēng)順，通過測(cè)試重試機(jī)制生效了，但是并沒有我想象的去請(qǐng)求另一臺(tái)健康的機(jī)子，于是被迫去吧開源碼看一看，最終發(fā)現(xiàn)是源碼的bug，不過已經(jīng)修復(fù)，升級(jí)版本即可。
代碼分析
使用的版本是
spring-cloud-netflix-core:1.3.6.RELEASE
spring-retry:1.2.1.RELEASE
spring cloud 依賴版本：
org.springframework.cloud
spring-cloud-dependencies
${spring-cloud.version}
pom
import
因?yàn)閱⒂昧酥卦?，所以?qǐng)求應(yīng)用時(shí)會(huì)執(zhí)行RetryableRibbonLoadBalancingHttpClient.execute方法：
public RibbonApacheHttpResponse execute(final RibbonApacheHttpRequest request, final IClientConfig configOverride) throws Exception {
final RequestConfig.Builder builder = RequestConfig.custom();
IClientConfig config = configOverride != null ? configOverride : this.config;
builder.setConnectTimeout(config.get(
CommonClientConfigKey.ConnectTimeout, this.connectTimeout));
builder.setSocketTimeout(config.get(
CommonClientConfigKey.ReadTimeout, this.readTimeout));
builder.setRedirectsEnabled(config.get(
CommonClientConfigKey.FollowRedirects, this.followRedirects));
final RequestConfig requestConfig = builder.build();
final LoadBalancedRetryPolicy retryPolicy = loadBalancedRetryPolicyFactory.create(this.getClientName(), this);
RetryCallback retryCallback = new RetryCallback() {
@Override
public RibbonApacheHttpResponse doWithRetry(RetryContext context) throws Exception {
//on retries the policy will choose the server and set it in the context
//extract the server and update the request being made
RibbonApacheHttpRequest newRequest = request;
if(context instanceof LoadBalancedRetryContext) {
ServiceInstance service = ((LoadBalancedRetryContext)context).getServiceInstance();
if(service != null) {
//Reconstruct the request URI using the host and port set in the retry context
newRequest = newRequest.withNewUri(new URI(service.getUri().getScheme(),
newRequest.getURI().getUserInfo(), service.getHost(), service.getPort(),
newRequest.getURI().getPath(), newRequest.getURI().getQuery(),
newRequest.getURI().getFragment()));
}
}
newRequest = getSecureRequest(request, configOverride);
HttpUriRequest httpUriRequest = newRequest.toRequest(requestConfig);
final HttpResponse httpResponse = RetryableRibbonLoadBalancingHttpClient.this.delegate.execute(httpUriRequest);
if(retryPolicy.retryableStatusCode(httpResponse.getStatusLine().getStatusCode())) {
if(CloseableHttpResponse.class.isInstance(httpResponse)) {
((CloseableHttpResponse)httpResponse).close();
}
throw new RetryableStatusCodeException(RetryableRibbonLoadBalancingHttpClient.this.clientName,
httpResponse.getStatusLine().getStatusCode());
}
return new RibbonApacheHttpResponse(httpResponse, httpUriRequest.getURI());
}
};
return this.executeWithRetry(request, retryPolicy, retryCallback);
}我們發(fā)現(xiàn)先new 一個(gè)RetryCallback，然后執(zhí)行this.executeWithRetry(request, retryPolicy, retryCallback);
而這個(gè)RetryCallback.doWithRetry的代碼我們清楚看到是實(shí)際請(qǐng)求的代碼，也就是說this.executeWithRetry方法最終還是會(huì)調(diào)用RetryCallback.doWithRetry
protected T doExecute(RetryCallback retryCallback,
RecoveryCallback 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);
if (this.logger.isTraceEnabled()) {
this.logger.trace("RetryContext retrieved: " + context);
}
// Make sure the context is available globally for clients who need
// it...
RetrySynchronizationManager.register(context);
Throwable lastException = null;
boolean exhausted = false;
try {
// Give clients a chance to enhance the context...
boolean running = doOpenInterceptors(retryCallback, context);
if (!running) {
throw new TerminatedRetryException(
"Retry terminated abnormally by interceptor before first attempt");
}
// Get or Start the backoff context...
BackOffContext backOffContext = null;
Object resource = context.getAttribute("backOffContext");
if (resource instanceof BackOffContext) {
backOffContext = (BackOffContext) resource;
}
if (backOffContext == null) {
backOffContext = backOffPolicy.start(context);
if (backOffContext != null) {
context.setAttribute("backOffContext", backOffContext);
}
}
/*
* We allow the whole loop to be skipped if the policy or context already
* forbid the first try. This is used in the case of external retry to allow a
* recovery in handleRetryExhausted without the callback processing (which
* would throw an exception).
*/
while (canRetry(retryPolicy, context) && !context.isExhaustedOnly()) {
try {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Retry: count=" + context.getRetryCount());
}
// Reset the last exception, so if we are successful
// the close interceptors will not think we failed...
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) {
lastException = e;
// back off was prevented by another thread - fail the retry
if (this.logger.isDebugEnabled()) {
this.logger
.debug("Abort retry because interrupted: count="
+ context.getRetryCount());
}
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.wrapIfNecessary(e);
}
}
/*
* A stateful attempt that can retry may rethrow the exception before now,
* but if we get this far in a stateful retry there's a reason for it,
* like a circuit breaker or a rollback classifier.
*/
if (state != null && context.hasAttribute(GLOBAL_STATE)) {
break;
}
}
if (state == null && this.logger.isDebugEnabled()) {
this.logger.debug(
"Retry failed last attempt: count=" + context.getRetryCount());
}
exhausted = true;
return handleRetryExhausted(recoveryCallback, context, state);
}
catch (Throwable e) {
throw RetryTemplate.wrapIfNecessary(e);
}
finally {
close(retryPolicy, context, state, lastException == null || exhausted);
doCloseInterceptors(retryCallback, context, lastException);
RetrySynchronizationManager.clear();
}
}
在一個(gè)while循環(huán)里實(shí)現(xiàn)重試機(jī)制，當(dāng)執(zhí)行retryCallback.doWithRetry(context)出現(xiàn)異常的時(shí)候，就會(huì)catch異常，然后用 retryPolicy判斷是否進(jìn)行重試，特別注意registerThrowable(retryPolicy, state, context, e);方法，不但判斷了是否重試，在重試情況下會(huì)新選出一個(gè)機(jī)子放入context，然后再去執(zhí)行retryCallback.doWithRetry(context)時(shí)帶入，如此就實(shí)現(xiàn)了換機(jī)子重試了。
但是我的配置怎么會(huì)沒有換機(jī)子呢？調(diào)試代碼發(fā)現(xiàn)registerThrowable(retryPolicy, state, context, e);選出來的機(jī)子沒問題，就是新的健康的機(jī)子，但是在執(zhí)行retryCallback.doWithRetry(context)代碼的時(shí)候依然請(qǐng)求的是那臺(tái)掛掉的機(jī)子。
所以我們?cè)僮屑?xì)看一下retryCallback.doWithRetry(context)的代碼：
我們發(fā)現(xiàn)了這行代碼：
newRequest = getSecureRequest(request, configOverride);
protected RibbonApacheHttpRequest getSecureRequest(RibbonApacheHttpRequest request, IClientConfig configOverride) {
if (isSecure(configOverride)) {
final URI secureUri = UriComponentsBuilder.fromUri(request.getUri())
.scheme("https").build(true).toUri();
return request.withNewUri(secureUri);
}
return request;
}newRequest在前面已經(jīng)使用context構(gòu)建完畢，request是上一次請(qǐng)求的數(shù)據(jù)，只要執(zhí)行這個(gè)代碼就會(huì)發(fā)現(xiàn)newRequest永遠(yuǎn)都會(huì)被request覆蓋?？吹竭@里我們才發(fā)現(xiàn)原來是一個(gè)源碼bug。
以上是“Spring Cloud請(qǐng)求重試機(jī)制的示例分析”這篇文章的所有內(nèi)容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內(nèi)容對(duì)大家有所幫助，如果還想學(xué)習(xí)更多知識(shí)，歡迎關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道！
網(wǎng)頁(yè)名稱：SpringCloud請(qǐng)求重試機(jī)制的示例分析
當(dāng)前地址：
http://weahome.cn/article/jgjcje.html
重慶分公司
重慶分公司
