Spring Cloud学习教程之Zuul统一异常处理与回退

前言

Zuul 是Netflix 提供的一个开源组件,致力于在云平台上提供动态路由，监控，弹性，安全等边缘服务的框架。也有很多公司使用它来作为网关的重要组成部分，碰巧今年公司的架构组决定自研一个网关产品，集动态路由，动态权限，限流配额等功能为一体，为其他部门的项目提供统一的外网调用管理，最终形成产品(这方面阿里其实已经有成熟的网关产品了，但是不太适用于个性化的配置，也没有集成权限和限流降级)。

本文主要给大家介绍了关于Spring Cloud Zuul统一异常处理与回退的相关内容，分享出来供大家参考学习，下面话不多说了，来一起看看详细的介绍吧。

一、Filter中统一异常处理

　　其实在SpringCloud的Edgware SR2版本中对于ZuulFilter中的错误有统一的处理，但是在实际开发当中对于错误的响应方式，我想每个团队都有自己的处理规范。那么如何做到自定义的异常处理呢？

我们可以先参考一下SpringCloud提供的SendErrorFilter:

/*
 * Copyright 2013-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cloud.netflix.zuul.filters.post;

import javax.servlet.RequestDispatcher;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.netflix.zuul.util.ZuulRuntimeException;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.StringUtils;

import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
import com.netflix.zuul.exception.ZuulException;

import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.ERROR_TYPE;
import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.SEND_ERROR_FILTER_ORDER;

/**
 * Error {@link ZuulFilter} that forwards to /error (by default) if {@link RequestContext#getThrowable()} is not null.
 *
 * @author Spencer Gibb
 */
//TODO: move to error package in Edgware
public class SendErrorFilter extends ZuulFilter {

 private static final Log log = LogFactory.getLog(SendErrorFilter.class);
 protected static final String SEND_ERROR_FILTER_RAN = "sendErrorFilter.ran";

 @Value("${error.path:/error}")
 private String errorPath;

 @Override
 public String filterType() {
  return ERROR_TYPE;
 }

 @Override
 public int filterOrder() {
  return SEND_ERROR_FILTER_ORDER;
 }

 @Override
 public boolean shouldFilter() {
  RequestContext ctx = RequestContext.getCurrentContext();
  // only forward to errorPath if it hasn't been forwarded to already
  return ctx.getThrowable() != null
    && !ctx.getBoolean(SEND_ERROR_FILTER_RAN, false);
 }

 @Override
 public Object run() {
  try {
   RequestContext ctx = RequestContext.getCurrentContext();
   ZuulException exception = findZuulException(ctx.getThrowable());
   HttpServletRequest request = ctx.getRequest();

   request.setAttribute("javax.servlet.error.status_code", exception.nStatusCode);

   log.warn("Error during filtering", exception);
   request.setAttribute("javax.servlet.error.exception", exception);

   if (StringUtils.hasText(exception.errorCause)) {
    request.setAttribute("javax.servlet.error.message", exception.errorCause);
   }

   RequestDispatcher dispatcher = request.getRequestDispatcher(
     this.errorPath);
   if (dispatcher != null) {
    ctx.set(SEND_ERROR_FILTER_RAN, true);
    if (!ctx.getResponse().isCommitted()) {
     ctx.setResponseStatusCode(exception.nStatusCode);
     dispatcher.forward(request, ctx.getResponse());
    }
   }
  }
  catch (Exception ex) {
   ReflectionUtils.rethrowRuntimeException(ex);
  }
  return null;
 }

 ZuulException findZuulException(Throwable throwable) {
  if (throwable.getCause() instanceof ZuulRuntimeException) {
   // this was a failure initiated by one of the local filters
   return (ZuulException) throwable.getCause().getCause();
  }

  if (throwable.getCause() instanceof ZuulException) {
   // wrapped zuul exception
   return (ZuulException) throwable.getCause();
  }

  if (throwable instanceof ZuulException) {
   // exception thrown by zuul lifecycle
   return (ZuulException) throwable;
  }

  // fallback, should never get here
  return new ZuulException(throwable, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, null);
 }

 public void setErrorPath(String errorPath) {
  this.errorPath = errorPath;
 }
}

在这里我们可以找到几个关键点：

　　1）在上述代码中，我们可以发现filter已经将相关的错误信息放到request当中了：

　　　　request.setAttribute("javax.servlet.error.status_code", exception.nStatusCode);

　　　　request.setAttribute("javax.servlet.error.exception", exception);

　　　　request.setAttribute("javax.servlet.error.message", exception.errorCause);

　　2）错误处理完毕后，会转发到 xxx/error的地址来处理

　　那么我们可以来做个试验,我们在gateway-service项目模块里，创建一个会抛出异常的filter:

package com.hzgj.lyrk.springcloud.gateway.server.filter;
import com.netflix.zuul.ZuulFilter;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
@Component
@Slf4j
public class MyZuulFilter extends ZuulFilter {
 @Override
 public String filterType() {
  return "post";
 }

 @Override
 public int filterOrder() {
  return 9;
 }

 @Override
 public boolean shouldFilter() {
  return true;
 }

 @Override
 public Object run() {
  log.info("run error test ...");
  throw new RuntimeException();
  // return null;
 }
}

　　紧接着我们定义一个控制器，来做错误处理：

package com.hzgj.lyrk.springcloud.gateway.server.filter;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;

@RestController
public class ErrorHandler {

 @GetMapping(value = "/error")
 public ResponseEntity<ErrorBean> error(HttpServletRequest request) {
  String message = request.getAttribute("javax.servlet.error.message").toString();
  ErrorBean errorBean = new ErrorBean();
  errorBean.setMessage(message);
  errorBean.setReason("程序出错");
  return new ResponseEntity<>(errorBean, HttpStatus.BAD_GATEWAY);
 }

 private static class ErrorBean {
  private String message;

  private String reason;

  public String getMessage() {
   return message;
  }

  public void setMessage(String message) {
   this.message = message;
  }

  public String getReason() {
   return reason;
  }

  public void setReason(String reason) {
   this.reason = reason;
  }
 }
}

　　启动项目后，我们通过网关访问一下试试：

二、关于zuul回退的问题

1、关于zuul的超时问题：

　　这个问题网上有很多解决方案,但是我还要贴一下源代码，请关注这个类 AbstractRibbonCommand，在这个类里集成了hystrix与ribbon。

/*
 * Copyright 2013-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package org.springframework.cloud.netflix.zuul.filters.route.support;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.cloud.netflix.ribbon.RibbonClientConfiguration;
import org.springframework.cloud.netflix.ribbon.RibbonHttpResponse;
import org.springframework.cloud.netflix.ribbon.support.AbstractLoadBalancingClient;
import org.springframework.cloud.netflix.ribbon.support.ContextAwareRequest;
import org.springframework.cloud.netflix.zuul.filters.ZuulProperties;
import org.springframework.cloud.netflix.zuul.filters.route.RibbonCommand;
import org.springframework.cloud.netflix.zuul.filters.route.RibbonCommandContext;
import org.springframework.cloud.netflix.zuul.filters.route.ZuulFallbackProvider;
import org.springframework.cloud.netflix.zuul.filters.route.FallbackProvider;
import org.springframework.http.client.ClientHttpResponse;
import com.netflix.client.AbstractLoadBalancerAwareClient;
import com.netflix.client.ClientRequest;
import com.netflix.client.config.DefaultClientConfigImpl;
import com.netflix.client.config.IClientConfig;
import com.netflix.client.config.IClientConfigKey;
import com.netflix.client.http.HttpResponse;
import com.netflix.config.DynamicIntProperty;
import com.netflix.config.DynamicPropertyFactory;
import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommandGroupKey;
import com.netflix.hystrix.HystrixCommandKey;
import com.netflix.hystrix.HystrixCommandProperties;
import com.netflix.hystrix.HystrixCommandProperties.ExecutionIsolationStrategy;
import com.netflix.hystrix.HystrixThreadPoolKey;
import com.netflix.zuul.constants.ZuulConstants;
import com.netflix.zuul.context.RequestContext;

/**
 * @author Spencer Gibb
 */
public abstract class AbstractRibbonCommand<LBC extends AbstractLoadBalancerAwareClient<RQ, RS>, RQ extends ClientRequest, RS extends HttpResponse>
  extends HystrixCommand<ClientHttpResponse> implements RibbonCommand {

 private static final Log LOGGER = LogFactory.getLog(AbstractRibbonCommand.class);
 protected final LBC client;
 protected RibbonCommandContext context;
 protected ZuulFallbackProvider zuulFallbackProvider;
 protected IClientConfig config;

 public AbstractRibbonCommand(LBC client, RibbonCommandContext context,
   ZuulProperties zuulProperties) {
  this("default", client, context, zuulProperties);
 }

 public AbstractRibbonCommand(String commandKey, LBC client,
   RibbonCommandContext context, ZuulProperties zuulProperties) {
  this(commandKey, client, context, zuulProperties, null);
 }

 public AbstractRibbonCommand(String commandKey, LBC client,
         RibbonCommandContext context, ZuulProperties zuulProperties,
         ZuulFallbackProvider fallbackProvider) {
  this(commandKey, client, context, zuulProperties, fallbackProvider, null);
 }

 public AbstractRibbonCommand(String commandKey, LBC client,
         RibbonCommandContext context, ZuulProperties zuulProperties,
         ZuulFallbackProvider fallbackProvider, IClientConfig config) {
  this(getSetter(commandKey, zuulProperties, config), client, context, fallbackProvider, config);
 }

 protected AbstractRibbonCommand(Setter setter, LBC client,
         RibbonCommandContext context,
         ZuulFallbackProvider fallbackProvider, IClientConfig config) {
  super(setter);
  this.client = client;
  this.context = context;
  this.zuulFallbackProvider = fallbackProvider;
  this.config = config;
 }

 protected static HystrixCommandProperties.Setter createSetter(IClientConfig config, String commandKey, ZuulProperties zuulProperties) {
  int hystrixTimeout = getHystrixTimeout(config, commandKey);
  return HystrixCommandProperties.Setter().withExecutionIsolationStrategy(
    zuulProperties.getRibbonIsolationStrategy()).withExecutionTimeoutInMilliseconds(hystrixTimeout);
 }

 protected static int getHystrixTimeout(IClientConfig config, String commandKey) {
  int ribbonTimeout = getRibbonTimeout(config, commandKey);
  DynamicPropertyFactory dynamicPropertyFactory = DynamicPropertyFactory.getInstance();
  int defaultHystrixTimeout = dynamicPropertyFactory.getIntProperty("hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds",
   0).get();
  int commandHystrixTimeout = dynamicPropertyFactory.getIntProperty("hystrix.command." + commandKey + ".execution.isolation.thread.timeoutInMilliseconds",
   0).get();
  int hystrixTimeout;
  if(commandHystrixTimeout > 0) {
   hystrixTimeout = commandHystrixTimeout;
  }
  else if(defaultHystrixTimeout > 0) {
   hystrixTimeout = defaultHystrixTimeout;
  } else {
   hystrixTimeout = ribbonTimeout;
  }
  if(hystrixTimeout < ribbonTimeout) {
   LOGGER.warn("The Hystrix timeout of " + hystrixTimeout + "ms for the command " + commandKey +
    " is set lower than the combination of the Ribbon read and connect timeout, " + ribbonTimeout + "ms.");
  }
  return hystrixTimeout;
 }

 protected static int getRibbonTimeout(IClientConfig config, String commandKey) {
  int ribbonTimeout;
  if (config == null) {
   ribbonTimeout = RibbonClientConfiguration.DEFAULT_READ_TIMEOUT + RibbonClientConfiguration.DEFAULT_CONNECT_TIMEOUT;
  } else {
   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 = (ribbonReadTimeout + ribbonConnectTimeout) * (maxAutoRetries + 1) * (maxAutoRetriesNextServer + 1);
  }
  return ribbonTimeout;
 }

 private static int getTimeout(IClientConfig config, String commandKey, String property, IClientConfigKey<Integer> configKey, int defaultValue) {
  DynamicPropertyFactory dynamicPropertyFactory = DynamicPropertyFactory.getInstance();
  return dynamicPropertyFactory.getIntProperty(commandKey + "." + config.getNameSpace() + "." + property, config.get(configKey, defaultValue)).get();
 }

 @Deprecated
 //TODO remove in 2.0.x
 protected static Setter getSetter(final String commandKey, ZuulProperties zuulProperties) {
  return getSetter(commandKey, zuulProperties, null);
 }

 protected static Setter getSetter(final String commandKey,
   ZuulProperties zuulProperties, IClientConfig config) {

  // @formatter:off
  Setter commandSetter = Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("RibbonCommand"))
        .andCommandKey(HystrixCommandKey.Factory.asKey(commandKey));
  final HystrixCommandProperties.Setter setter = createSetter(config, commandKey, zuulProperties);
  if (zuulProperties.getRibbonIsolationStrategy() == ExecutionIsolationStrategy.SEMAPHORE){
   final String name = ZuulConstants.ZUUL_EUREKA + commandKey + ".semaphore.maxSemaphores";
   // we want to default to semaphore-isolation since this wraps
   // 2 others commands that are already thread isolated
   final DynamicIntProperty value = DynamicPropertyFactory.getInstance()
     .getIntProperty(name, zuulProperties.getSemaphore().getMaxSemaphores());
   setter.withExecutionIsolationSemaphoreMaxConcurrentRequests(value.get());
  } else if (zuulProperties.getThreadPool().isUseSeparateThreadPools()) {
   final String threadPoolKey = zuulProperties.getThreadPool().getThreadPoolKeyPrefix() + commandKey;
   commandSetter.andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey(threadPoolKey));
  }

  return commandSetter.andCommandPropertiesDefaults(setter);
  // @formatter:on
 }

 @Override
 protected ClientHttpResponse run() throws Exception {
  final RequestContext context = RequestContext.getCurrentContext();

  RQ request = createRequest();
  RS response;

  boolean retryableClient = this.client instanceof AbstractLoadBalancingClient
    && ((AbstractLoadBalancingClient)this.client).isClientRetryable((ContextAwareRequest)request);

  if (retryableClient) {
   response = this.client.execute(request, config);
  } else {
   response = this.client.executeWithLoadBalancer(request, config);
  }
  context.set("ribbonResponse", response);

  // Explicitly close the HttpResponse if the Hystrix command timed out to
  // release the underlying HTTP connection held by the response.
  //
  if (this.isResponseTimedOut()) {
   if (response != null) {
    response.close();
   }
  }

  return new RibbonHttpResponse(response);
 }

 @Override
 protected ClientHttpResponse getFallback() {
  if(zuulFallbackProvider != null) {
   return getFallbackResponse();
  }
  return super.getFallback();
 }

 protected ClientHttpResponse getFallbackResponse() {
  if (zuulFallbackProvider instanceof FallbackProvider) {
   Throwable cause = getFailedExecutionException();
   cause = cause == null ? getExecutionException() : cause;
   if (cause == null) {
    zuulFallbackProvider.fallbackResponse();
   } else {
    return ((FallbackProvider) zuulFallbackProvider).fallbackResponse(cause);
   }
  }
  return zuulFallbackProvider.fallbackResponse();
 }

 public LBC getClient() {
  return client;
 }

 public RibbonCommandContext getContext() {
  return context;
 }

 protected abstract RQ createRequest() throws Exception;
}

　　请注意：getRibbonTimeout方法与getHystrixTimeout方法，其中这两个方法 commandKey的值为路由的名称，比如说我们访问:http://localhost:8088/order-server/xxx来访问order-server服务， 那么commandKey 就为order-server

　　根据源代码，我们先设置gateway-server的超时参数：

#全局的ribbon设置
ribbon:
 ConnectTimeout: 3000
 ReadTimeout: 3000
hystrix:
 command:
 default:
  execution:
  isolation:
   thread:
   timeoutInMilliseconds: 3000
zuul:
 host:
 connectTimeoutMillis: 10000

　　当然也可以单独为order-server设置ribbon的超时参数：order-server.ribbon.xxxx=xxx , 为了演示zuul中的回退效果，我在这里把Hystrix超时时间设置短一点。当然最好不要将Hystrix默认的超时时间设置的比Ribbon的超时时间短，源码里遇到此情况已经给与我们警告了。

　　那么我们在order-server下添加如下方法：

@GetMapping("/sleep/{sleepTime}")
 public String sleep(@PathVariable Long sleepTime) throws InterruptedException {
  TimeUnit.SECONDS.sleep(sleepTime);
  return "SUCCESS";
 }

2、zuul的回退方法

我们可以实现ZuulFallbackProvider接口,实现代码：

package com.hzgj.lyrk.springcloud.gateway.server.filter;
import com.google.common.collect.ImmutableMap;
import com.google.gson.GsonBuilder;
import org.springframework.cloud.netflix.zuul.filters.route.ZuulFallbackProvider;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.stereotype.Component;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.time.LocalDateTime;
import java.time.LocalTime;
@Component
public class FallBackHandler implements ZuulFallbackProvider {

 @Override
 public String getRoute() {
  //代表所有的路由都适配该设置
  return "*";
 }

 @Override
 public ClientHttpResponse fallbackResponse() {
  return new ClientHttpResponse() {
   @Override
   public HttpStatus getStatusCode() throws IOException {
    return HttpStatus.OK;
   }

   @Override
   public int getRawStatusCode() throws IOException {
    return 200;
   }

   @Override
   public String getStatusText() throws IOException {
    return "OK";
   }

   @Override
   public void close() {

   }

   @Override
   public InputStream getBody() throws IOException {
    String result = new GsonBuilder().create().toJson(ImmutableMap.of("errorCode", 500, "content", "请求失败", "time", LocalDateTime.now()));
    return new ByteArrayInputStream(result.getBytes());
   }

   @Override
   public HttpHeaders getHeaders() {
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_JSON);
    return headers;
   }
  };
 }
}

此时我们访问：http://localhost:8088/order-server/sleep/6 得到如下结果：

当我们访问：http://localhost:8088/order-server/sleep/1 就得到如下结果：

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对我们的支持。

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