记一次线上SpringCloud-Feign请求服务超时异常排查

由于近期线上单量暴涨，第三方反馈部分工单业务存在查询处理失败现象，经排查是当前系统通过FeignClient调用下游系统出现部分超时失败（异常代码贴在下方）。

Caused by: feign.RetryableException: Read timed out executing POST http://xxxx
        at feign.FeignException.errorExecuting(FeignException.java:84) ~[feign-core-10.1.0.jar!/:na]
        at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:113) ~[feign-core-10.1.0.jar!/:na]
        at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:78) ~[feign-core-10.1.0.jar!/:na]
        at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103) ~[feign-core-10.1.0.jar!/:na]
        at com.sun.proxy.$Proxy141.creditReportConvert(Unknown Source) ~[na:na]
Caused by: java.net.SocketTimeoutException: Read timed out
        at java.net.SocketInputStream.socketRead0(Native Method) ~[na:1.8.0_121]
        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116) ~[na:1.8.0_121]
        at java.net.SocketInputStream.read(SocketInputStream.java:171) ~[na:1.8.0_121]
        at java.net.SocketInputStream.read(SocketInputStream.java:141) ~[na:1.8.0_121]
        at java.io.BufferedInputStream.fill(BufferedInputStream.java:246) ~[na:1.8.0_121]
        at java.io.BufferedInputStream.read1(BufferedInputStream.java:286) ~[na:1.8.0_121]
        at java.io.BufferedInputStream.read(BufferedInputStream.java:345) ~[na:1.8.0_121]
        at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:704) ~[na:1.8.0_121]
        at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:647) ~[na:1.8.0_121]
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1569) ~[na:1.8.0_121]
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1474) ~[na:1.8.0_121]
        at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:480) ~[na:1.8.0_121]
        at feign.Client$Default.convertResponse(Client.java:143) ~[feign-core-10.1.0.jar!/:na]
        at feign.Client$Default.execute(Client.java:68) ~[feign-core-10.1.0.jar!/:na]
        at org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer.execute(FeignLoadBalancer.java:93) ~[spring-cloud-openfeign-core-2.1.1.RELEASE.jar!/:2.1.1.RELEASE]
        at org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer.execute(FeignLoadBalancer.java:56) ~[spring-cloud-openfeign-core-2.1.1.RELEASE.jar!/:2.1.1.RELEASE]
        at com.netflix.client.AbstractLoadBalancerAwareClient$1.call(AbstractLoadBalancerAwareClient.java:104) ~[ribbon-loadbalancer-2.3.0.jar!/:2.3.0]
        at com.netflix.loadbalancer.reactive.LoadBalancerCommand$3$1.call(LoadBalancerCommand.java:303) ~[ribbon-loadbalancer-2.3.0.jar!/:2.3.0]

通过系统慢请求捕捉拦截，发现当前请求仅耗时1031毫秒，就触发Read timed out超时错误，本项目与下游项目均注册在Eureka上面，对这个1秒就超时感到很迷惑，于是开始查阅底层源码之旅。

通过跟踪代码可以在feign.Request内部类Options构造函数默认配置连接超时10秒，读超时60秒。然而本次调用请求仅耗时1秒左右就被掐断连接提示超时错误，初步判断默认这个超时配置并未生效导致。

写到这，咱们先回顾下Feign链路完整调用流程步骤。

可以看出Feign调用分为Hystrix、Ribbon两层，一般高版本的Hystrix默认是关闭的（本项目Hystrix默认是关闭的，那么现在需要去分析Ribbon层调用配置信息）

可以看到RibbonClientConfiguration默认配置的读超时和连接超时时间1000毫秒=1秒，在没有配置超时情况下当前这个超时是符合本次调用超时错误触发。

我们可以在FeignLoadBalancer的execute方法中看到当IClientConfig为空的时候进行覆盖超时时间，默认是取Ribbon的超时时间，并不是Feign Options默认的超时时间。

public FeignLoadBalancer(ILoadBalancer lb, IClientConfig clientConfig,
            ServerIntrospector serverIntrospector) {
        super(lb, clientConfig);
        this.setRetryHandler(RetryHandler.DEFAULT);
        this.clientConfig = clientConfig;
        this.ribbon = RibbonProperties.from(clientConfig);
        RibbonProperties ribbon = this.ribbon;
        this.connectTimeout = ribbon.getConnectTimeout();
        this.readTimeout = ribbon.getReadTimeout();
        this.serverIntrospector = serverIntrospector;
    }

如果application.properties文件中有配置超时时间，则使用配置的超时时间。否则是取Ribbon默认的超时时间，也就是网上所说的Feign调用服务的默认时长是1秒钟，也就是如果超过1秒没连接上或者超过1秒没响应，那么会相应的报错。

实际业务中服务如果响应时间超过1秒，咱们可以按照实际响应情况给予配置相对应的超时时间，下面分别贴出properties和yml版本的配置

#properties版本

feign.client.config.default.connectTimeout=60000
feign.client.config.default.readTimeout=60000

#yml版本

feign:
  client:
    config:
      default:
        connectTimeout: 60000
        readTimeout: 60000