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，谢谢大家对的支持。