spring cloud feign调用超时重试retryer

迈不过友情╰ 2023-02-20 12:14 23阅读 0赞

*  认识一下`Retryer`接口
 *  认识一下`RetryableException`异常
 *  认识一下`FeignException`异常
 *  实际中我们是如何来应用的

#### Retry 接口 简单介绍 ####

*  通过下面的源码，`Retry`接口继承了`Cloneable`接口。
 *  `Retry`接口里面有一个方法叫`continueOrPropagate`,参数是一个`RetryableException`重试异常的对象，返回值为`void`类型
 *  `Retry`接口还有 一个`clone()`方法，返回类型是`Retryer`
 *  该接口里面有个静态内部类`Default`，并且实现了`Retryer`接口
    
     *  该类有一个默认构造函数，还有一个有参数的构造函数

源码如下：

package feign;
    
    import static java.util.concurrent.TimeUnit.SECONDS;
    
    对于克隆每次调用`Client.execute(Request, Request.Options)` 实现可以保持状态，以确定是否重试操作应该继续。
    public interface Retryer extends Cloneable { 
    
      /** * 如果重试被允许，返回（睡觉后可能）。 否则传播例外。 */
      void continueOrPropagate(RetryableException e);
    
      Retryer clone();
    
      public static class Default implements Retryer { 
    
        // 最大重试次数
        private final int maxAttempts;
        // 重试的间隔
        private final long period;
        // 最大重试间隔
        private final long maxPeriod;
        int attempt;
        long sleptForMillis;
    
        // Default类的默认无参构造函数，
        // 重试间隔100 ms，最大重试间隔1s，最大重试次数默认5次
        public Default() { 
          this(100, SECONDS.toMillis(1), 5);
        }
    
        // 重试间隔，最大重试间隔，最大重试次数，attempt默认是1
        public Default(long period, long maxPeriod, int maxAttempts) { 
          this.period = period;
          this.maxPeriod = maxPeriod;
          this.maxAttempts = maxAttempts;
          this.attempt = 1;
        }
    
        // visible for testing;
        protected long currentTimeMillis() { 
          return System.currentTimeMillis();
        }
    
        // 重写了Retryer的方法continueOrPropagate
        public void continueOrPropagate(RetryableException e) { 
          // 如果重试的次数attempt大于最大重试次数，则抛出重试异常对象RetryableException
          if (attempt++ >= maxAttempts) { 
            throw e;
          }
    
          long interval;
          if (e.retryAfter() != null) { 
            interval = e.retryAfter().getTime() - currentTimeMillis();
            if (interval > maxPeriod) { 
              interval = maxPeriod;
            }
            if (interval < 0) { 
              return;
            }
          } else { 
            interval = nextMaxInterval();
          }
          try { 
            Thread.sleep(interval);
          } catch (InterruptedException ignored) { 
            Thread.currentThread().interrupt();
          }
          sleptForMillis += interval;
        }
    
        /** * 计算时间间隔为重试尝试。 的间隔呈指数增加每次尝试，在nextInterval * = 1.5（其中，1.5是回退因子）的速率，在最大间隔。 * @return 时间从现在纳秒，直到下一次尝试。 */
        long nextMaxInterval() { 
          long interval = (long) (period * Math.pow(1.5, attempt - 1));
          return interval > maxPeriod ? maxPeriod : interval;
        }
    
        @Override
        public Retryer clone() { 
          return new Default(period, maxPeriod, maxAttempts);
        }
      }
    
      /** * 实现永不重试请求。 它传播RetryableException */
      Retryer NEVER_RETRY = new Retryer() { 
    
        @Override
        public void continueOrPropagate(RetryableException e) { 
          throw e;
        }
    
        @Override
        public Retryer clone() { 
          return this;
        }
      };
    }

#### RetryableException简单介绍 ####

*  该异常继承`FeignException`，也是一个`RuntimeException`
 *  里面有一个定义的`Long`类型的变量`retryAfter`
 *  该类有两个构造函数，分别是：
    
     *  `RetryableException(String message, Throwable cause, Date retryAfter)`
     *  `RetryableException(String message, Date retryAfter)`
 *  该类还有一个无参数的方法，叫做`retryAfter`，会返回一个`Date`类型

源码如下：

package feign;
    
    import java.util.Date;
    
    /** * 当引发此异常Response被认为是可重试，通常经由feign.codec.ErrorDecoder当status是503 */
    public class RetryableException extends FeignException { 
    
      private static final long serialVersionUID = 1L;
    
      private final Long retryAfter;
    
      /** * retryAfter -通常对应于Util.RETRY_AFTER报头。 */
      public RetryableException(String message, Throwable cause, Date retryAfter) { 
        super(message, cause);
        this.retryAfter = retryAfter != null ? retryAfter.getTime() : null;
      }
    
      /** * retryAfter -通常对应于Util.RETRY_AFTER报头。 */
      public RetryableException(String message, Date retryAfter) { 
        super(message);
        this.retryAfter = retryAfter != null ? retryAfter.getTime() : null;
      }
    
      /** * http->503 服务不可用 * 有时对应于Util.RETRY_AFTER存在于报头503的状态。 其他的时间就从专用响应解析。 空如果不明 */
      public Date retryAfter() { 
        return retryAfter != null ? new Date(retryAfter) : null;
      }
    }

#### FeignException 简单介绍 ####

*  该类继承了`RuntimeException`
 *  有一个`int`类型的私有变量`status`，用来表示`HTTP`的状态码
 *  有三个方法，分别是:
    
     *  `errorReading(Request request, Response ignored, IOException cause)`
     *  `errorStatus(String methodKey, Response response)`
     *  `errorExecuting(Request request, IOException cause)`
 *  主要异常是`I/O`类的可以进行重试，404无重试效果

源码如下：

package feign;
    
    import java.io.IOException;
    
    import static java.lang.String.format;
    
    public class FeignException extends RuntimeException { 
    
      private static final long serialVersionUID = 0;
      // HTTP status
      private int status;
    
      protected FeignException(String message, Throwable cause) { 
        super(message, cause);
      }
    
      protected FeignException(String message) { 
        super(message);
      }
    
      protected FeignException(int status, String message) { 
        super(message);
        this.status = status;
      }
    
      public int status() { 
        return this.status;
      }
    
      static FeignException errorReading(Request request, Response ignored, IOException cause) { 
        return new FeignException(
            format("%s reading %s %s", cause.getMessage(), request.method(), request.url()),
            cause);
      }
    
      public static FeignException errorStatus(String methodKey, Response response) { 
        String message = format("status %s reading %s", response.status(), methodKey);
        try { 
          if (response.body() != null) { 
            String body = Util.toString(response.body().asReader());
            message += "; content:\n" + body;
          }
        } catch (IOException ignored) {  // NOPMD
        }
        return new FeignException(response.status(), message);
      }
    
      static FeignException errorExecuting(Request request, IOException cause) { 
        return new RetryableException(
            format("%s executing %s %s", cause.getMessage(), request.method(), request.url()), cause,
            null);
      }
    }

#### 如何在项目中应用重试机制？ ####

在上面的介绍中，可以知道`Retryer`接口，`Default`类，重试异常类`RetryerException`，我们可以通过重写`Retryer`接口的方法`continueOrPropagate`来实现重试，比如：

@Slf4j
    public class ConnectTimeoutRetryer extends Retryer.Default { 
        Supplier<Stream<String>> streamSupplier = () -> Stream.of("connect timed out");
    
        public ConnectTimeoutRetryer(){ 
            super();
        }
    
        @Override
        public void continueOrPropagate(RetryableException e) { 
    				// 在kibana上可以分析prd上由于feign超时，都会在cause里面有connect time out关键字，因此这里做判断，如果异常原因里面都不是connect time out的，会打印ConnectTimeoutRetryerFeign failed,并抛出RetryableException对象e
            if (streamSupplier.get().noneMatch(x -> e.getCause().getMessage().contains(x))) { 
                log.warn("ConnectTimeoutRetryerFeign failed", e);
                throw e;
            }
            log.error("begin to retry：{} ,{}" , e.getMessage(), e);
            super.continueOrPropagate(e);
        }
    
        //重写retryer的clone方法
        @Override
        public Retryer clone() { 
            return new ConnectTimeoutRetryer();
        }
    }

我们这个方案，主要是解决，各个微服务的`feign`调用之间超时问题，比如网络不稳定等原因导致的。

下面是重试时的堆栈信息：

2020-05-28 21:17:08,954 [hystrix-zis-zzzz-193] ERROR [com.xxxx.common.service.share.feign.ConnectTimeoutRetryer] [?:?] [trace=xxx,span=xxx] - begin to retry：connect timed out executing POST http://xxx.com/search/rrr ,{ } feign.RetryableException: connect timed out executing POST http://xxx.com/search/rrr at feign.FeignException.errorExecuting(FeignException.java:67) at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:104) at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76) at feign.hystrix.HystrixInvocationHandler$1.run(HystrixInvocationHandler.java:108) 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:10211) at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:51) at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:35) at rx.Observable.unsafeSubscribe(Observable.java:10211) 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:10211) 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$1.call(HystrixContexSchedulerAction.java:47) at org.springframework.cloud.sleuth.instrument.hystrix.SleuthHystrixConcurrencyStrategy$HystrixTraceCallable.call(SleuthHystrixConcurrencyStrategy.java:188) 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$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: java.net.SocketTimeoutException: connect timed out at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) at java.net.Socket.connect(Socket.java:589) at sun.net.NetworkClient.doConnect(NetworkClient.java:175) at sun.net.www.http.HttpClient.openServer(HttpClient.java:463) at sun.net.www.http.HttpClient.openServer(HttpClient.java:558) at sun.net.www.http.HttpClient.<init>(HttpClient.java:242) at sun.net.www.http.HttpClient.New(HttpClient.java:339) at sun.net.www.http.HttpClient.New(HttpClient.java:357) at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1220) at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1156) at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1050) at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:984) at sun.net.www.protocol.http.HttpURLConnection.getOutputStream0(HttpURLConnection.java:1334) at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:1309) at feign.Client$Default.convertAndSend(Client.java:133) at feign.Client$Default.execute(Client.java:73) at org.springframework.cloud.sleuth.instrument.web.client.feign.TraceFeignClient.execute(TraceFeignClient.java:92) at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:97) ... 32 common frames omitted

缺点：该方案是可以解决各个微服务之间`feign`调用超时的问题，但是`Supplier<Stream<String>> streamSupplier = () -> Stream.of("connect timed out");`灵活度不够，只有堆栈`cause`中有`connect time out`的时候才会抛出重试异常`RetryerException`去进行重试。  
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