spring cloud zuul 配置全局回退无效的原因

最新推荐文章于 2021-04-05 20:19:56 发布

置顶 qiang_gege

最新推荐文章于 2021-04-05 20:19:56 发布

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分类专栏： spring cloud 文章标签： spring cloud zuul 配置全局回退不生效

本文链接：https://blog.youkuaiyun.com/qq_41293765/article/details/80911414

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本文分析了 Spring Cloud Zuul 中路由配置导致的回退失效问题，并给出了具体的解决方案。通过对比不同路由配置和服务转发过滤器，解释了如何通过调整配置启用全局回退。

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首先，spring cloud 的版本为 Edgware.SR3
自定义FallbackProvider 的实现请点击这里，大神写的很详细；

起初我的bootstrap.yml 配置服务路由为：

routes:
    auth-server:
      strip-prefix: true
      sensitiveHeaders:
      path: /v1/auth-api/**
      url: http://localhost:8002/
    system-server:
      strip-prefix: true
      sensitiveHeaders:
      path: /v1/system-api/**
      url: http://localhost:8004/

配置完MyServerFallbackProvider之后启动项目发现回退没生效，还是一直抛异常：com.netflix.zuul.exception.ZuulException:Connect to localhost:8004 [localhost/127.0.0.1, localhost/0:0:0:0:0:0:0:1] failed: Connection refused: connect
at org.springframework.cloud.netflix.zuul.util.ZuulRuntimeException.<init>(ZuulRuntimeException.java:33)
at org.springframework.cloud.netflix.zuul.filters.route.SimpleHostRoutingFilter.run(SimpleHostRoutingFilter.java:207)
at com.netflix.zuul.ZuulFilter.runFilter(ZuulFilter.java:112)
at com.netflix.zuul.FilterProcessor.processZuulFilter(FilterProcessor.java:193)
at com.netflix.zuul.FilterProcessor.runFilters(FilterProcessor.java:157)
at com.netflix.zuul.FilterProcessor.route(FilterProcessor.java:118)
at com.netflix.zuul.ZuulRunner.route(ZuulRunner.java:96)

最终查看源码得知抛出异常而没有回退发现和zull 的默认 filter有关；对zuul 过滤器不了解的小伙伴点击这里，一下为zuul 的默认过滤器

类型	顺序	过滤器	功能
pre	-3	ServletDetectionFilter	标记处理Servlet的类型
pre	-2	Servlet30WrapperFilter	包装HttpServletRequest请求
pre	-1	FormBodyWrapperFilter	包装请求体
route	1	DebugFilter	标记调试标志
route	5	PreDecorationFilter	处理请求上下文供后续使用
route	10	RibbonRoutingFilter	serviceId请求转发
route	100	SimpleHostRoutingFilter	url请求转发
route	500	SendForwardFilter	forward请求转发
post	0	SendErrorFilter	处理有错误的请求响应
post	1000	SendResponseFilter	处理正常的请求响应

由于我的bootstrap.yml 路由配置为 url 形式（上文bootstrap.yml标红的部分），所以server 转发filter 为 SimpleHostRoutingFilter，最终通过hettpclient转发到服务端，而SimpleHostRoutingFilter的run()方法中直接抛出了ZuulRuntimeException:

try {
   CloseableHttpResponse response = forward(this.httpClient, verb, uri, request,
         headers, params, requestEntity);
   setResponse(response);
}
catch (Exception ex) {
   throw new ZuulRuntimeException(ex);
}
return null;

SimpleHostRoutingFilter的forwardRequest()方法：

private CloseableHttpResponse forwardRequest(CloseableHttpClient httpclient,
      HttpHost httpHost, HttpRequest httpRequest) throws IOException {
   return httpclient.execute(httpHost, httpRequest);
}

至此回退不生效的原因已找到，将bootstrap.yml中服务的路由方式更改为 serviceId形式，默认转发filter为RibbonRoutingFilter

routes:
  auth-server:
    strip-prefix: true
    sensitiveHeaders:
    path: /v1/auth-api/**
    serviceId: auth-server
  system-server:
    strip-prefix: true
    sensitiveHeaders:
    path: /v1/system-api/**
    serviceId: system-server

RibbonRoutingFilter 中的转发方法：

protected ClientHttpResponse forward(RibbonCommandContext context) throws Exception {
   Map<String, Object> info = this.helper.debug(context.getMethod(),
         context.getUri(), context.getHeaders(), context.getParams(),
         context.getRequestEntity());

   RibbonCommand command = this.ribbonCommandFactory.create(context);
   try {
      ClientHttpResponse response = command.execute();
      this.helper.appendDebug(info, response.getRawStatusCode(), response.getHeaders());
      return response;
   }
   catch (HystrixRuntimeException ex) {
      return handleException(info, ex);
   }

}