com.netflix.zuul.exception.ZuulException: Forwarding error

场景

项目基于SpringCloud，生产者做了负载，消费者（此处用的ribbon + restTemplcate）做了降级(hystrix)，当一个消费者关掉后，访问网关（zuul），出现如下错误：

com.netflix.zuul.exception.ZuulException: Forwarding error
	at org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter.handleException(RibbonRoutingFilter.java:183) ~[spring-cloud-netflix-core-1.3.1.RELEASE.jar:1.3.1.RELEASE]
	at org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter.forward(RibbonRoutingFilter.java:158) ~[spring-cloud-netflix-core-1.3.1.RELEASE.jar:1.3.1.RELEASE]
	at org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter.run(RibbonRoutingFilter.java:106) ~[spring-cloud-netflix-core-1.3.1.RELEASE.jar:1.3.1.RELEASE]
	at com.netflix.zuul.ZuulFilter.runFilter(ZuulFilter.java:112) ~[zuul-core-1.3.0.jar:1.3.0]
	at com.netflix.zuul.FilterProcessor.processZuulFilter(FilterProcessor.java:193) ~[zuul-core-1.3.0.jar:1.3.0]
	at com.netflix.zuul.FilterProcessor.runFilters(FilterProcessor.java:157) ~[zuul-core-1.3.0.jar:1.3.0]
	at com.netflix.zuul.FilterProcessor.route(FilterProcessor.java:118) ~[zuul-core-1.3.0.jar:1.3.0]
	at com.netflix.zuul.ZuulRunner.route(ZuulRunner.java:96) ~[zuul-core-1.3.0.jar:1.3.0]
	at com.netflix.zuul.http.ZuulServlet.route(ZuulServlet.java:116) ~[zuul-core-1.3.0.jar:1.3.0]
	at com.netflix.zuul.http.ZuulServlet.service(ZuulServlet.java:81) ~[zuul-core-1.3.0.jar:1.3.0]
................... 省略一大片..............

解决方法

在网关服务中的配置文件中配置如下信息：

zuul:
  okhttp:
    enabled: true # 使用okhttp方式请求，正常来说okhttp比较速度快一点
  semaphore:
      max-semaphores: 500 # 并发处理数，值越大越好，但到到达一个临界点之后，就不会提高响应速度了
  host:
    socket-timeout-millis: 30000 # socket超时时间，如果使用service-id方式是不用配置的
    connect-timeout-millis: 30000 # 连接时间semaphores
    max-total-connections: 5000  # 最大连接数，值越大越好，但到到达一个临界点之后，就不会提高响应速度了
    max-per-route-connections: 5 # 每个router最大连接数，降低请求时间，越小越好，但达到一定层级就没用了

hystrix:
  command:
    default:
      execution:
        isolation:
          thread:
            timeoutInMilliseconds: 30000 # Hystrix超时时间
          strategy: THREAD

ribbon:
  ReadTimeout: 20000 # 处理时间
  ConnectTimeout: 20000 # 连接时间
  MaxAutoRetries: 0 #最大自动重试次数
  MaxAutoRetriesNextServer: 1 # 换实例重试次数
  MaxTotalHttpConnections: 2000 # 最大http连接数，越大越好，但到到达一个临界点之后，就不会提高响应速度了
  MaxConnectionsPerHost: 1000 # 每个host连接数

注：解决方案来源于网上，具体链接没有找到。