Zuul：在服务不可用的情况下自动将传入请求重新路由到其他服务实例

问题描述

我已经以某种方式为Zuul和Eureka进行了配置，即服务的3个相同实例并行运行。我在端口8400上呼叫网关，该网关以循环方式将传入请求路由到端口8420、8430和8440。它工作顺利。现在，如果我关闭这三项服务之一，则少量传入请求将出错，但有以下异常：

com.netflix.zuul.exception.ZuulException: Filter threw Exception
    => 1: java.util.concurrent.FutureTask.report(FutureTask.java:122)
    => 3: hu.perit.spvitamin.core.batchprocessing.BatchProcessor.process(BatchProcessor.java:106)
    caused by: com.netflix.zuul.exception.ZuulException: Filter threw Exception
    => 1: com.netflix.zuul.FilterProcessor.processZuulFilter(FilterProcessor.java:227)
    caused by: org.springframework.cloud.netflix.zuul.util.ZuulRuntimeException: com.netflix.zuul.exception.ZuulException: Forwarding error
    => 1: org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter.run(RibbonRoutingFilter.java:124)
    caused by: com.netflix.zuul.exception.ZuulException: Forwarding error
    => 1: org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter.handleException(RibbonRoutingFilter.java:198)
    caused by: com.netflix.client.ClientException: com.netflix.client.ClientException
    => 1: com.netflix.client.AbstractLoadBalancerAwareClient.executeWithLoadBalancer(AbstractLoadBalancerAwareClient.java:118)
    caused by: java.lang.RuntimeException: org.apache.http.NoHttpResponseException: scalable-service-2:8430 failed to respond
    => 1: rx.exceptions.Exceptions.propagate(Exceptions.java:57)
    caused by: org.apache.http.NoHttpResponseException: scalable-service-2:8430 failed to respond
    => 1: org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:141)

我的Zuul路由如下：

### Zuul routes
zuul.routes.scalable-service.path=/scalable/**
#Authorization header will be forwarded to scalable-service
zuul.routes.scalable-service.sensitiveHeaders: Cookie,Set-Cookie
zuul.routes.scalable-service.serviceId=template-scalable-service

Eureka需要一段时间才能发现该服务不再可用。

我的问题是：是否可以配置Zuul，以便在出现NoHttpResponseException的情况下将请求转发到池中的另一个可用实例？

解决方法

Eureka默认情况下要求每90s更新一次租赁。也就是说，如果服务实例没有在90s中续约，Eureka服务器将驱逐该实例。对于您而言，instance尚未被撤出-实例的续订窗口有效。

为此，您可以按照here.所述通过在renew和eureka client上进行配置设置来缩短eureka server的持续时间

注意：如果您点击了actuator /shutdown端点，则实例将立即evicted

,

最后，我找到了解决问题的方法。合适的搜索词组是“容错”。关键是以下application.properties文件中的autoretry配置。如果要获得3个池化服务，则必须将template-scalable-service.ribbon.MaxAutoRetriesNextServer的值至少设置为6，以实现完全的容错能力。通过该设置，我可以随时杀死3个服务中的2个，没有传入请求会出错。最后，我将其设置为10，没有不必要的超时增加，hystrix会中断该行。

### Eureka config
eureka.instance.hostname=${hostname:localhost}
eureka.instance.instanceId=${eureka.instance.hostname}:${spring.application.name}:${server.port}
eureka.instance.non-secure-port-enabled=false
eureka.instance.secure-port-enabled=true
eureka.instance.secure-port=${server.port}
eureka.instance.lease-renewal-interval-in-seconds=5
eureka.instance.lease-expiration-duration-in-seconds=10

eureka.datacenter=perit.hu
eureka.environment=${EUREKA_ENVIRONMENT_PROFILE:dev}
eureka.client.serviceUrl.defaultZone=${EUREKA_SERVER:https://${server.fqdn}:${server.port}/eureka}
eureka.client.server.waitTimeInMsWhenSyncEmpty=0
eureka.client.registry-fetch-interval-seconds=5
eureka.dashboard.path=/gui

eureka.server.enable-self-preservation=false
eureka.server.expected-client-renewal-interval-seconds=10
eureka.server.eviction-interval-timer-in-ms=2000

### Ribbon
ribbon.IsSecure=true
ribbon.NFLoadBalancerPingInterval=5
ribbon.ConnectTimeout=30000
ribbon.ReadTimeout=120000

### Zuul config
zuul.host.connectTimeoutMillis=30000
zuul.host.socketTimeoutMillis=120000
zuul.host.maxTotalConnections=2000
zuul.host.maxPerRouteConnections=200
zuul.retryable=true

### Zuul routes
#template-scalable-service
zuul.routes.scalable-service.path=/scalable/**
#Authorization header will be forwarded to scalable-service
zuul.routes.scalable-service.sensitiveHeaders=Cookie,Set-Cookie
zuul.routes.scalable-service.serviceId=template-scalable-service
# Autoretry config for template-scalable-service
template-scalable-service.ribbon.MaxAutoRetries=0
template-scalable-service.ribbon.MaxAutoRetriesNextServer=10
template-scalable-service.ribbon.OkToRetryOnAllOperations=true

#template-auth-service
zuul.routes.auth-service.path=/auth/**
#Authorization header will be forwarded to scalable-service
zuul.routes.auth-service.sensitiveHeaders=Cookie,Set-Cookie
zuul.routes.auth-service.serviceId=template-auth-service
# Autoretry config for template-auth-service
template-auth-service.ribbon.MaxAutoRetries=0
template-auth-service.ribbon.MaxAutoRetriesNextServer=0
template-auth-service.ribbon.OkToRetryOnAllOperations=false

### Hystrix
hystrix.command.default.execution.timeout.enabled=false

除此之外，我在application-discovery.properties中有一个特定于配置文件的设置

#Microservice environment
eureka.client.registerWithEureka=false
eureka.client.fetchRegistry=true
spring.cloud.loadbalancer.ribbon.enabled=true

我在这样的docker容器中启动服务器：

services:
    discovery:
        container_name: discovery
        image: template-eureka
        environment:
            #agentlib for remote debugging
            - JAVA_OPTS=-DEUREKA_SERVER=https://discovery:8400/eureka -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005
            - TEMPLATE_EUREKA_OPTS=-Dspring.profiles.active=default,dev,discovery
            - EUREKA_ENVIRONMENT_PROFILE=dev
        ports:
            - '8400:8400'
            - '5500:5005'

        networks: 
            - back-tier-net
            - monitoring
        hostname: 'discovery'

在GitHub.中查看完整的解决方案