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

Question

我已经用 Eureka 配置了 Zuul，一个服务的 3 个相同实例并行工作。我在端口 8400 上调用网关，它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 3 个服务中的一个，少量传入请求将出错，并出现以下异常：

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 路由是这样的：

### 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 发现服务不再可用需要一段时间。

我的问题是：是否有可能配置 Zuul，以便在出现 NoHttpResponseException 时将请求转发到池中的另一个可用实例？

Answer 1

Eureka，默认情况下，需要每 90s 续订租约。也就是说，如果服务实例没有在 90s 中续订租约，Eureka 服务器将驱逐该实例。在您的情况下，instance 尚未被驱逐 - 该实例的更新 window 有效。

为此，您可以通过 eureka client 和 eureka server 处的配置设置减少 renew 持续时间，如 here.

所述

注意：如果你点击actuator /shutdown端点，实例立即evicted

Answer 2

终于找到了解决问题的方法。合适的搜索短语是 'fault tolerance'。关键是以下 application.properties 文件中的自动重试配置。在 3 个池化服务的情况下，template-scalable-service.ribbon.MaxAutoRetriesNextServer 的值必须至少设置为 6 才能实现完全容错。使用该设置，我可以随时终止 3 个服务中的 2 个，传入请求不会出错。最后我已经设置为10了，没有不必要的超时增加，hystrix会断线。

### 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 容器中启动我的服务器：

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'

请参阅 GitHub.

中的完整解决方案

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

Zuul: automatic rerouting incoming requests to other service instance in case of unavailable service

java

spring-cloud

netflix-eureka

netflix-zuul