聊聊openfeign的超时和重试

openfeign是一种声明式的http客户端，它可以方便地集成到springcloud，像调用本地方法一样使用http方式调用远程服务。今天我们来聊一聊feign的超时和重试。

构建环境

注：本文使用的openfeign版本：2.1.0.RELEASE

在pom文件中增加下面配置：

<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId><version>2.1.0.RELEASE</version>
</dependency>

openfeign默认使用java原生的URLConnection。这里我们要选择一个http的客户端，比如选择apache的，需要在application.properties文件中增加下面这个配置：

feign.httpclient.enabled=true

同时需要在pom文件中引入下面这个jar包：

<dependency><groupId>io.github.openfeign</groupId><artifactId>feign-httpclient</artifactId><version>9.3.1</version>
</dependency>

我们也可以选择okhttp的，这时需要在application.properties文件中增加下面这个配置：

feign.okhttp.enabled=true

同时需要在pom文件中进入okhttp的jar包：

<dependency><groupId>io.github.openfeign</groupId><artifactId>feign-okhttp</artifactId><version>10.2.0</version>
</dependency>

在我本地的实验中，有一个服务叫springboot-mybatis，eureka地址是localhost:8889，在application.properties文件中加入下面配置：

eureka.instance.hostname=localhost
eureka.instance.prefer-ip-address=true
eureka.client.serviceUrl.defaultZone=http://${eureka.instance.hostname}:8889/eureka/

boot启动类加上下面这个注解：

@EnableFeignClients

这样就初步实现了一个openfeign的配置，我在服务端工程(springboot-mybatis)中增加了一个方法，让客户端来调用，代码如下：

@Controller
@RequestMapping("/feign")
public class FeignTestController {@RequestMapping("/feignReadTimeout")@ResponseBodypublic String getEmployeebyName() throws InterruptedException {//这里配置10s的超时时间，给后面的实验用Thread.currentThread().sleep(10000);return "success";}
}

在feign客户端的调用代码如下：

@FeignClient("springboot-mybatis")
public interface FeignAsEurekaClient {@GetMapping("/feign/feignReadTimeout")String feignReadTimeout();
}

超时配置

注:下面的实验使用的是okhttp来进行的。

上面实现了一个简单的feign使用demo，不过feign的使用还有很多需要注意的地方，这里我们来聊一聊超时。先看第一种情况，feign客户端和服务端都注册在一个eureka的情况。

1.不配置超时时间，默认"读超时60s"

上面的demo我们没有设置超时时间，所以虽然服务端响应延迟10s，请求还是能成功的。

但是上面的"读超时60s"我加了引号，为什么呢？在feign.Request里面有一个内部类，如果不配置超时，外部会调用下面这个构造函数，连接超时10s，读超时60s

public Options() {this(10 * 1000, 60 * 1000);
}

如果我们没有配置feign超时时间，上面的时间也会被ribbon覆盖？请求连接时间和超时时间，默认为1秒，在RibbonClientConfiguration类定义，被覆盖后也是会读超时的。

覆盖超时时间设置的代码在FeignLoadBalancer，代码如下：

public RibbonResponse execute(RibbonRequest request, IClientConfig configOverride)throws IOException {Request.Options options;if (configOverride != null) {RibbonProperties override = RibbonProperties.from(configOverride);options = new Request.Options(override.connectTimeout(this.connectTimeout),override.readTimeout(this.readTimeout));}else {options = new Request.Options(this.connectTimeout, this.readTimeout);}Response response = request.client().execute(request.toRequest(), options);return new RibbonResponse(request.getUri(), response);
}

所以我们加入下面的配置，把ribbon的读超时时间调大，也是可以解决读超时问题的：

ribbon.okhttp.enabled=true
#ribbon.ConnectTimeout=2000
#请求处理的超时时间
ribbon.ReadTimeout=10000

但ribbon是一个做负载均衡的，我们还是给feign定义超时时间比较好。因为feign配置了超时时间后，会最后赋值给Options的超时时间。在FeignClientFactoryBean类的configureUsingProperties方法。

if (config.getConnectTimeout() != null && config.getReadTimeout() != null) {builder.options(new Request.Options(config.getConnectTimeout(), config.getReadTimeout()));
}

2.配置一个默认超时时间

feign.client.config.default.connectTimeout=2000
feign.client.config.default.readTimeout=5000

这里我配置了连接超时是2s，读取超时是5s，这样，上面demo中的请求就失败了，要想成功，readTimeout不能低于10000。

3.为单个服务设置超时时间

如果我们有一个接口超时时间很长，要全局都设置一个这么长的超时时间吗？这样会有问题，一个平时响应很快的接口，如果服务端出故障了，我们应该让它fail-fast。这样我们就需要对慢的接口或服务单独设置超时时间。

对某一个服务设置单独的超时时间，配置如下：

#对单个服务设置超时，会覆盖默认的超时
feign.client.config.springboot-mybatis.connectTimeout=2000
feign.client.config.springboot-mybatis.readTimeout=11000

4.为单个接口设置超时时间

还是上面的问题，一个服务有多个接口，只有一个超级慢，那对整个服务的所有接口设置一个超时时间也会影响其他接口的fail-fast，我们需要对单个接口设置超时时间，就得配合hystrix来配置了，配置如下：

#开启熔断
#feign.hystrix.enabled=true#开启超时熔断，默认为true,如果为false，则熔断机制只在服务不可用时开启,这个配置不加，使用默认配置
#hystrix.command.default.execution.timeout.enabled=false#如果上面一个配置是true，设置超时熔断时间,因为openfeign中的熔断时间默认是1s,太短了，我们必须手工设置一个
#hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=15000
#下面的配置为单个接口设置超时时间
#xxx:要设置的某个FeignClient的类名
#yyy：方法名
#zzz：参数，如果是基础类型，就直接填基础类型：String/int；如果是某个对象，就直接填对象的类名
#hystrix.command.xxx#yyy(zzz).execution.isolation.thread.timeoutInMilliseconds=1000
#hystrix.command.FeignAsHttpCient#feignReadTimeout().execution.isolation.thread.timeoutInMilliseconds=23000

这里必须注意一下，ribbon的读超时时间也不能小于接口的返回时间，不然回报ribbon超时，所以ribbon配置如下：

ribbon.ConnectTimeout=2000
ribbon.ReadTimeout=11000

这里我必须说明一下，如果配置了feign的超时时间，并且feign的读超时不够，熔断的超时时间是不起作用的。坑爹啊。原因是什么呢？有待研究。

原因：这里hystrix的时间其实并没有起作用，起作用的其实还是feign的超时时间

那不是说openfeign如果给单个服务设置了超时时间，或设置了默认超时时间，就不能给单个响应慢的接口设置超时时间了吗？

下面我们看第二种情况，使用feign作为http客户端来调用外部的服务情况。这种情况的客户端我也给出一个，服务的接口还是刚刚那个：

@FeignClient(name = "feign", url = "http://localhost:8083")
public interface FeignAsHttpCient {@GetMapping("/feign/feignReadTimeout")String feignReadTimeout();
}

这里我们需要在application.properties文件中增加下面这个配置就可以了：

hystrix.command.FeignAsHttpCient#feignReadTimeout().execution.isolation.thread.timeoutInMilliseconds=11000

注意：这里hystrix的时间其实并没有起作用，起作用的其实还是feign的超时时间

那对单个接口怎么设置超时时间呢，我给出一个参考，如下：

public class RestTemplateConfiguration {@Beanpublic OkHttp3ClientHttpRequestFactory okHttp3RequestFactory(){OkHttp3ClientHttpRequestFactory requestFactory = new OkHttp3ClientHttpRequestFactory();//注意：这里配置了超时时间，就不受ribbon超时时间的影响了requestFactory.setConnectTimeout(2000);requestFactory.setReadTimeout(15000);return requestFactory;}@Bean@LoadBalancedpublic RestTemplate restTemplate(OkHttp3ClientHttpRequestFactory okHttp3RequestFactory){return new RestTemplate(okHttp3RequestFactory);}
}

如果作为eureka客户端，需要加@LoadBalanced的注解，发送请求代码如下，springboot-mybatis是请求的服务名：

String response = restTemplate.getForObject("http://springboot-mybatis/feign/feignReadTimeout", String.class);

如果作为普通http客户端，不能加@LoadBalanced的注解，发送请求代码如下：

String response = restTemplate.getForObject("http://localhost:8083/feign/feignReadTimeout", String.class);

重试配置

如果不配置，openfeign默认是不重试的，看FeignClientsConfiguration中的代码：

@Bean
@ConditionalOnMissingBean
public Retryer feignRetryer() {return Retryer.NEVER_RETRY;
}

再看一下Retryer中的NEVER_RETRY定义：

/*** Implementation that never retries request. It propagates the RetryableException.*/
Retryer NEVER_RETRY = new Retryer() {@Overridepublic void continueOrPropagate(RetryableException e) {throw e;}@Overridepublic Retryer clone() {return this;}
};

下面我给出一个重试的配置：

@Configuration
public class FeignConfigure {@Beanpublic Retryer feignRetryer(){// period=100 发起当前请求的时间间隔,单位毫秒// maxPeriod=1000 发起当前请求的最大时间间隔,单位毫秒// maxAttempts=2 重试次数是1，因为包括第一次，所以我们如果想要重试2次，就需要设置为3Retryer retryer = new Retryer.Default(100, 1000, 2);return retryer;}
}

注意：

hystrix是在ribbon外面，所以hystrix的超时时间不能小于ribbon的(ConnectTimeout + ReadTimeout) * maxAttempts
这样才能保证在Ribbon里的请求还没结束时，Hystrix的熔断时间不会超时

比如下面这个配置：

#feign.client.config.springboot-mybatis.connectTimeout=2000
#feign.client.config.springboot-mybatis.readTimeout=5000
hystrix.command.FeignAsEurekaClient#feignReadTimeout().execution.isolation.thread.timeoutInMilliseconds=15000
ribbon.ReadTimeout=5000

这个时候再执行测试用例FeignAsEurekaClient.feignReadTimeout,打印日志如下，可以看到有2次请求，第2次是重试：

2020-11-10 09:34:42,011 [main] [INFO] org.springframework.test.context.transaction.TransactionContext - Began transaction (1) for test context [DefaultTestContext@587e5365 testClass = TestFeignAsEurekaClient, testInstance = boot.service.TestFeignAsEurekaClient@26b3fd41, testMethod = testFeignReadTimeOut@TestFeignAsEurekaClient, testException = [null], mergedContextConfiguration = [WebMergedContextConfiguration@22fcf7ab testClass = TestFeignAsEurekaClient, locations = '{}', classes = '{class boot.Application, class boot.Application}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true, server.port=0}', contextCustomizers = set[org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@f4168b8, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@74294adb, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer@11c20519, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@25359ed8], resourceBasePath = 'src/main/webapp', contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.web.ServletTestExecutionListener.activateListener' -> false]]; transaction manager [org.springframework.jdbc.datasource.DataSourceTransactionManager@56f3f9da]; rollback [true]
2020-11-10 09:34:42,664 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] ---> GET http://springboot-mybatis/feign/feignReadTimeout HTTP/1.1
2020-11-10 09:34:42,664 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] ---> END HTTP (0-byte body)
2020-11-10 09:34:42,975 [hystrix-springboot-mybatis-1] [INFO] com.netflix.config.ChainedDynamicProperty - Flipping property: springboot-mybatis.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647
2020-11-10 09:34:43,002 [hystrix-springboot-mybatis-1] [INFO] com.netflix.util.concurrent.ShutdownEnabledTimer - Shutdown hook installed for: NFLoadBalancer-PingTimer-springboot-mybatis
2020-11-10 09:34:43,003 [hystrix-springboot-mybatis-1] [INFO] com.netflix.loadbalancer.BaseLoadBalancer - Client: springboot-mybatis instantiated a LoadBalancer: DynamicServerListLoadBalancer:{NFLoadBalancer:name=springboot-mybatis,current list of Servers=[],Load balancer stats=Zone stats: {},Server stats: []}ServerList:null
2020-11-10 09:34:43,011 [hystrix-springboot-mybatis-1] [INFO] com.netflix.loadbalancer.DynamicServerListLoadBalancer - Using serverListUpdater PollingServerListUpdater
2020-11-10 09:34:43,066 [hystrix-springboot-mybatis-1] [INFO] com.netflix.config.ChainedDynamicProperty - Flipping property: springboot-mybatis.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647
2020-11-10 09:34:43,071 [hystrix-springboot-mybatis-1] [INFO] com.netflix.loadbalancer.DynamicServerListLoadBalancer - DynamicServerListLoadBalancer for client springboot-mybatis initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=springboot-mybatis,current list of Servers=[10.192.84.93:8083],Load balancer stats=Zone stats: {defaultzone=[Zone:defaultzone;   Instance count:1;   Active connections count: 0;    Circuit breaker tripped count: 0;   Active connections per server: 0.0;]
},Server stats: [[Server:10.192.84.93:8083; Zone:defaultZone;   Total Requests:0;   Successive connection failure:0;    Total blackout seconds:0;   Last connection made:Thu Jan 01 08:00:00 CST 1970;  First connection made: Thu Jan 01 08:00:00 CST 1970;    Active Connections:0;   total failure count in last (1000) msecs:0; average resp time:0.0;  90 percentile resp time:0.0;    95 percentile resp time:0.0;    min resp time:0.0;  max resp time:0.0;  stddev resp time:0.0]
]}ServerList:org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList@77f618f
2020-11-10 09:34:44,028 [PollingServerListUpdater-0] [INFO] com.netflix.config.ChainedDynamicProperty - Flipping property: springboot-mybatis.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647
2020-11-10 09:34:53,266 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] <--- ERROR SocketTimeoutException: Read timed out (10600ms)
2020-11-10 09:34:53,267 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] java.net.SocketTimeoutException: Read timed outat java.net.SocketInputStream.socketRead0(Native Method)at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)at java.net.SocketInputStream.read(SocketInputStream.java:171)at java.net.SocketInputStream.read(SocketInputStream.java:141)at okio.Okio$2.read(Okio.java:139)at okio.AsyncTimeout$2.read(AsyncTimeout.java:237)at okio.RealBufferedSource.indexOf(RealBufferedSource.java:345)at okio.RealBufferedSource.readUtf8LineStrict(RealBufferedSource.java:217)at okio.RealBufferedSource.readUtf8LineStrict(RealBufferedSource.java:211)at okhttp3.internal.http1.Http1Codec.readResponseHeaders(Http1Codec.java:189)at okhttp3.internal.http.CallServerInterceptor.intercept(CallServerInterceptor.java:75)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:45)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:120)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:67)at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:185)at okhttp3.RealCall.execute(RealCall.java:69)at feign.okhttp.OkHttpClient.execute(OkHttpClient.java:167)at org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer.execute(FeignLoadBalancer.java:90)at org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer.execute(FeignLoadBalancer.java:56)at com.netflix.client.AbstractLoadBalancerAwareClient$1.call(AbstractLoadBalancerAwareClient.java:104)at com.netflix.loadbalancer.reactive.LoadBalancerCommand$3$1.call(LoadBalancerCommand.java:303)at com.netflix.loadbalancer.reactive.LoadBalancerCommand$3$1.call(LoadBalancerCommand.java:287)at rx.internal.util.ScalarSynchronousObservable$3.call(ScalarSynchronousObservable.java:231)at rx.internal.util.ScalarSynchronousObservable$3.call(ScalarSynchronousObservable.java:228)at rx.Observable.unsafeSubscribe(Observable.java:10151)at rx.internal.operators.OnSubscribeConcatMap$ConcatMapSubscriber.drain(OnSubscribeConcatMap.java:286)at rx.internal.operators.OnSubscribeConcatMap$ConcatMapSubscriber.onNext(OnSubscribeConcatMap.java:144)at com.netflix.loadbalancer.reactive.LoadBalancerCommand$1.call(LoadBalancerCommand.java:185)at com.netflix.loadbalancer.reactive.LoadBalancerCommand$1.call(LoadBalancerCommand.java:180)at rx.Observable.unsafeSubscribe(Observable.java:10151)at rx.internal.operators.OnSubscribeConcatMap.call(OnSubscribeConcatMap.java:94)at rx.internal.operators.OnSubscribeConcatMap.call(OnSubscribeConcatMap.java:42)at rx.Observable.unsafeSubscribe(Observable.java:10151)at rx.internal.operators.OperatorRetryWithPredicate$SourceSubscriber$1.call(OperatorRetryWithPredicate.java:127)at rx.internal.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.enqueue(TrampolineScheduler.java:73)at rx.internal.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.schedule(TrampolineScheduler.java:52)at rx.internal.operators.OperatorRetryWithPredicate$SourceSubscriber.onNext(OperatorRetryWithPredicate.java:79)at rx.internal.operators.OperatorRetryWithPredicate$SourceSubscriber.onNext(OperatorRetryWithPredicate.java:45)at rx.internal.util.ScalarSynchronousObservable$WeakSingleProducer.request(ScalarSynchronousObservable.java:276)at rx.Subscriber.setProducer(Subscriber.java:209)at rx.internal.util.ScalarSynchronousObservable$JustOnSubscribe.call(ScalarSynchronousObservable.java:138)at rx.internal.util.ScalarSynchronousObservable$JustOnSubscribe.call(ScalarSynchronousObservable.java:129)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)at rx.Observable.subscribe(Observable.java:10247)at rx.Observable.subscribe(Observable.java:10214)at rx.observables.BlockingObservable.blockForSingle(BlockingObservable.java:444)at rx.observables.BlockingObservable.single(BlockingObservable.java:341)at com.netflix.client.AbstractLoadBalancerAwareClient.executeWithLoadBalancer(AbstractLoadBalancerAwareClient.java:112)at org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient.execute(LoadBalancerFeignClient.java:65)at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:108)at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:78)at feign.hystrix.HystrixInvocationHandler$1.run(HystrixInvocationHandler.java:106)at com.netflix.hystrix.HystrixCommand$2.call(HystrixCommand.java:302)at com.netflix.hystrix.HystrixCommand$2.call(HystrixCommand.java:298)at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:46)at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:35)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)at rx.Observable.unsafeSubscribe(Observable.java:10151)at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:51)at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:35)at rx.Observable.unsafeSubscribe(Observable.java:10151)at rx.internal.operators.OnSubscribeDoOnEach.call(OnSubscribeDoOnEach.java:41)at rx.internal.operators.OnSubscribeDoOnEach.call(OnSubscribeDoOnEach.java:30)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)at rx.Observable.unsafeSubscribe(Observable.java:10151)at rx.internal.operators.OperatorSubscribeOn$1.call(OperatorSubscribeOn.java:94)at com.netflix.hystrix.strategy.concurrency.HystrixContexSchedulerAction$1.call(HystrixContexSchedulerAction.java:56)at com.netflix.hystrix.strategy.concurrency.HystrixContexSchedulerAction$1.call(HystrixContexSchedulerAction.java:47)at com.netflix.hystrix.strategy.concurrency.HystrixContexSchedulerAction.call(HystrixContexSchedulerAction.java:69)at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)at java.util.concurrent.FutureTask.run(FutureTask.java:266)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)at java.lang.Thread.run(Thread.java:745)2020-11-10 09:34:53,267 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] <--- END ERROR
2020-11-10 09:34:53,267 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] ---> RETRYING
2020-11-10 09:34:53,268 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] ---> GET http://springboot-mybatis/feign/feignReadTimeout HTTP/1.1
2020-11-10 09:34:53,268 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] ---> END HTTP (0-byte body)2020-11-10 09:34:58,270 [hystrix-springboot-mybatis-1] [WARN] com.netflix.config.sources.URLConfigurationSource - No URLs will be polled as dynamic configuration sources.
2020-11-10 09:34:58,271 [hystrix-springboot-mybatis-1] [INFO] com.netflix.config.sources.URLConfigurationSource - To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
2020-11-10 09:34:58,272 [hystrix-springboot-mybatis-1] [INFO] com.netflix.config.DynamicPropertyFactory - DynamicPropertyFactory is initialized with configuration sources: com.netflix.config.ConcurrentCompositeConfiguration@5f87f8d3
2020-11-10 09:34:58,274 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] <--- ERROR InterruptedIOException: thread interrupted (5006ms)
2020-11-10 09:34:58,275 [hystrix-springboot-mybatis-1] [DEBUG] boot.feign.FeignAsEurekaClient - [FeignAsEurekaClient#feignReadTimeout] java.io.InterruptedIOException: thread interruptedat okio.Timeout.throwIfReached(Timeout.java:145)at okio.Okio$1.write(Okio.java:76)at okio.AsyncTimeout$1.write(AsyncTimeout.java:180)at okio.RealBufferedSink.flush(RealBufferedSink.java:216)at okhttp3.internal.http1.Http1Codec.finishRequest(Http1Codec.java:166)at okhttp3.internal.http.CallServerInterceptor.intercept(CallServerInterceptor.java:72)at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:92)

而如果把配置改成下面的配置，就只有一次请求了，没有进行重试：

#feign.client.config.springboot-mybatis.connectTimeout=2000
#feign.client.config.springboot-mybatis.readTimeout=5000
hystrix.command.FeignAsEurekaClient#feignReadTimeout().execution.isolation.thread.timeoutInMilliseconds=8000
ribbon.ConnectTimeout=2000
ribbon.ReadTimeout=5000

这里也要注意：如果使用feign作为普通http客户端(不是eureka客户端)，是没有重试功能的。

总结

使用openfeign作为http客户端使用起来非常方便，不过也要注意一些复杂场景，比如作为eureka客户端对单个接口设置超时时间，配置比较复杂，需要借助熔断，而且跟整体服务的超时不兼容。
使用openfeign作为普通http客户端，重试功能不能作用。

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