Spring Cloud中，Eureka常见问题总结

浅浅的花香味﹌ 2022-05-30 02:07 172阅读 0赞

Spring Cloud中，Eureka常见问题总结。

##  ##

## 指定Eureka的Environment ##

参考文档：[https://github.com/Netflix/eureka/wiki/Configuring-Eureka][https_github.com_Netflix_eureka_wiki_Configuring-Eureka]

## 指定Eureka的DataCenter ##

参考文档：[https://github.com/Netflix/eureka/wiki/Configuring-Eureka][https_github.com_Netflix_eureka_wiki_Configuring-Eureka]  
文中指出，配置-Deureka.datacenter=cloud，这样eureka将会知道是在AWS云上。

## 如何解决Eureka注册服务慢的问题 ##

使用配置项：

参考文档：  
[http://cloud.spring.io/spring-cloud-static/Camden.SR1/\#\_why\_is\_it\_so\_slow\_to\_register\_a\_service][http_cloud.spring.io_spring-cloud-static_Camden.SR1_why_is_it_so_slow_to_register_a_service]  
原文：

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    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);">
      Why 
     <span style="color:rgb(194,98,48);">is</span> it 
     <span style="color:rgb(194,98,48);">so</span> Slow 
     <span style="color:rgb(194,98,48);">to</span> Register 
     <span style="color:rgb(194,98,48);">a</span> Service? 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);"></div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);">
      Being an instance also involves a periodic heartbeat to the registry (via the client’s serviceUrl) with default duration 30 seconds. A service is not available for discovery by clients until the instance, the server and the client all have the same metadata in their local 
     <span style="color:rgb(194,98,48);">cache</span> (so it could take 
     <span style="color:rgb(165,194,97);">3</span> heartbeats). You can 
     <span style="color:rgb(194,98,48);">change</span> the 
     <span style="color:rgb(194,98,48);">period</span> 
     <span style="color:rgb(194,98,48);">using</span> eureka.instance.leaseRenewalIntervalInSeconds 
     <span style="color:rgb(194,98,48);">and</span> this will speed up the process 
     <span style="color:rgb(194,98,48);">of</span> getting clients connected 
     <span style="color:rgb(194,98,48);">to</span> other services. 
     <span style="color:rgb(194,98,48);">In</span> production it’s probably better 
     <span style="color:rgb(194,98,48);">to</span> stick 
     <span style="color:rgb(194,98,48);">with</span> the 
     <span style="color:rgb(194,98,48);">default</span> because there 
     <span style="color:rgb(194,98,48);">are</span> 
     <span style="color:rgb(194,98,48);">some</span> computations internally 
     <span style="color:rgb(194,98,48);">in</span> the 
     <span style="color:rgb(194,98,48);">server</span> that make assumptions about the lease renewal period. 
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翻译：

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    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);">
      作为实例还涉及到与注册中心的周期性心跳，默认持续时间为 
     <span style="color:rgb(165,194,97);">30</span>秒（通过serviceUrl）。在实例、服务器、客户端都在本地缓存中具有相同的元数据之前，服务不可用于客户端发现（所以可能需要 
     <span style="color:rgb(165,194,97);">3</span>次心跳）。你可以使用eureka 
     <span style="color:rgb(155,112,63);">.instance</span> 
     <span style="color:rgb(155,112,63);">.leaseRenewalIntervalInSeconds</span> 配置，这将加快客户端连接到其他服务的过程。在生产中，最好坚持使用默认值，因为在服务器内部有一些计算，他们对续约做出假设。 
    </div></td> 
  </tr> 
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</table>

## Eureka的自我保护模式 ##

如果在Eureka Server的首页看到以下这段提示，则说明Eureka已经进入了保护模式。

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    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);"> 
     <span style="color:rgb(194,98,48);">EMERGENCY</span>!&nbsp; 
     <span style="color:rgb(194,98,48);">EUREKA</span>&nbsp; 
     <span style="color:rgb(194,98,48);">MAY</span>&nbsp; 
     <span style="color:rgb(194,98,48);">BE</span>&nbsp; 
     <span style="color:rgb(194,98,48);">INCORRECTLY</span>&nbsp; 
     <span style="color:rgb(194,98,48);">CLAIMING</span>&nbsp; 
     <span style="color:rgb(194,98,48);">INSTANCES</span>&nbsp; 
     <span style="color:rgb(194,98,48);">ARE</span>&nbsp; 
     <span style="color:rgb(194,98,48);">UP</span>&nbsp; 
     <span style="color:rgb(194,98,48);">WHEN</span>&nbsp;THEY'RE&nbsp; 
     <span style="color:rgb(194,98,48);">NOT</span>.&nbsp;RENEWALS&nbsp;ARE&nbsp;LESSER&nbsp;THAN&nbsp;THRESHOLD&nbsp; 
     <span style="color:rgb(194,98,48);">AND</span>&nbsp;HENCE&nbsp;THE&nbsp;INSTANCES&nbsp;ARE&nbsp; 
     <span style="color:rgb(194,98,48);">NOT</span>&nbsp;BEING&nbsp;EXPIRED&nbsp;JUST&nbsp;TO&nbsp;BE&nbsp;SAFE. 
    </div></td> 
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保护模式主要用于一组客户端和Eureka Server之间存在网络分区场景下的保护。一旦进入保护模式，Eureka Server将会尝试保护其服务注册表中的信息，不再删除服务注册表中的数据（也就是不会注销任何微服务）。

详见：[https://github.com/Netflix/eureka/wiki/Understanding-Eureka-Peer-to-Peer-Communication][https_github.com_Netflix_eureka_wiki_Understanding-Eureka-Peer-to-Peer-Communication]

## 如何解决Eureka Server不踢出已关停的节点的问题 ##

在开发过程中，我们常常希望Eureka Server能够迅速有效地踢出已关停的节点，但是新手由于Eureka自我保护模式，以及心跳周期长的原因，常常会遇到Eureka Server不踢出已关停的节点的问题。解决方法如下：

(1) Eureka Server端：配置关闭自我保护，并按需配置Eureka Server清理无效节点的时间间隔。

(2) Eureka Client端：配置开启健康检查，并按需配置续约更新时间和到期时间。

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    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);"> 
     <span style="color:rgb(194,98,48);">eureka</span> 
     <span style="color:rgb(155,112,63);">.client</span> 
     <span style="color:rgb(155,112,63);">.healthcheck</span> 
     <span style="color:rgb(155,112,63);">.enabled</span> # 开启健康检查（需要 
     <span style="color:rgb(194,98,48);">spring-boot-starter-actuator</span>依赖） 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);">
      eureka.instance.lease-renewal-interval- 
     <span style="color:rgb(194,98,48);">in</span>-seconds 
     <span style="color:rgb(188,148,88);font-style:italic;"># 续约更新时间间隔（默认30秒）</span> 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);">
      eureka.instance.lease-expiration-duration- 
     <span style="color:rgb(194,98,48);">in</span>-seconds 
     <span style="color:rgb(188,148,88);font-style:italic;"># 续约到期时间（默认90秒）</span> 
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示例：  
服务器端配置：

客户端配置：

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    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);"> 
     <span style="color:rgb(165,194,97);">eureka:</span> 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);"> 
     <span style="color:rgb(109,156,190);"> client:</span> 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);"> 
     <span style="color:rgb(109,156,190);"> healthcheck:</span> 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);"> 
     <span style="color:rgb(109,156,190);"> enabled:</span> 
     <span>true</span> 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);"> 
     <span style="color:rgb(109,156,190);"> instance:</span> 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);">
      lease-expiration-duration- 
     <span style="color:rgb(194,98,48);">in</span>- 
     <span style="color:rgb(165,194,97);">seconds:</span> 
     <span style="color:rgb(165,194,97);">30</span> 
    </div> 
    <div style="padding:.5em;color:rgb(230,225,220);background-color:rgb(35,35,35);">
      lease-renewal-interval- 
     <span style="color:rgb(194,98,48);">in</span>- 
     <span style="color:rgb(165,194,97);">seconds:</span> 
     <span style="color:rgb(165,194,97);">10</span> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

注意：  
更改Eureka更新频率将打破服务器的自我保护功能，生产环境下不建议自定义这些配置。  
详见：[https://github.com/spring-cloud/spring-cloud-netflix/issues/373][https_github.com_spring-cloud_spring-cloud-netflix_issues_373]

## 自定义Eureka的Instance ID ##

在Spring Cloud中，服务的Instance ID的默认值是`${spring.cloud.client.hostname}:${spring.application.name}:${spring.application.instance_id:${server.port}}`，也就是`机器主机名:应用名称:应用端口` 。因此在Eureka Server首页中看到的服务的信息类似如下：`itmuch:microservice-provider-user:8000` 。如果想要自定义这部分的信息怎么办？

示例：

eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:8761/eureka/
      instance:
        preferIpAddress: true
        instance-id: ${spring.cloud.client.ipAddress}:${server.port}        # 将Instance ID设置成IP:端口的形式

## Eureka配置最佳实践参考 ##

[https://github.com/spring-cloud/spring-cloud-netflix/issues/203][https_github.com_spring-cloud_spring-cloud-netflix_issues_203]

## 注意点：eureka.client.healthcheck.enabled=true配置项必须设置在application.yml中 ##

`eureka.client.healthcheck.enabled=true` 只应该在application.yml中设置。如果设置在bootstrap.yml中将会导致一些不良的副作用，例如在Eureka中注册的应用名称是UNKNOWN等。

##     ##

## 转自:http://www.itmuch.com/spring-cloud-sum-eureka/ ##

[https_github.com_Netflix_eureka_wiki_Configuring-Eureka]: https://github.com/Netflix/eureka/wiki/Configuring-Eureka
[http_cloud.spring.io_spring-cloud-static_Camden.SR1_why_is_it_so_slow_to_register_a_service]: http://cloud.spring.io/spring-cloud-static/Camden.SR1/#_why_is_it_so_slow_to_register_a_service
[https_github.com_Netflix_eureka_wiki_Understanding-Eureka-Peer-to-Peer-Communication]: https://github.com/Netflix/eureka/wiki/Understanding-Eureka-Peer-to-Peer-Communication
[https_github.com_spring-cloud_spring-cloud-netflix_issues_373]: https://github.com/spring-cloud/spring-cloud-netflix/issues/373
[https_github.com_spring-cloud_spring-cloud-netflix_issues_203]: https://github.com/spring-cloud/spring-cloud-netflix/issues/203