了解Spring Cloud Eureka服务器自我保护和更新阈值(Understanding Spring Cloud Eureka Server self preservation and renew threshold)

 我是开发微服务的新手，虽然我一直在研究一段时间，阅读Spring的文档和Netflix的文档。 
 
 我已经开始在Github上提供一个简单的项目。 它基本上是一个尤里卡服务器（阿基米德）和三个尤里卡客户端微服务器（一个公共API和两个私有的）。 检查github的自述文件是否有详细描述。 
 
 关键是当一切正在运行时，我希望如果其中一个私有微服务被杀死，则Eureka服务器实现并将其从注册表中删除。 
 
 我在Stackoverflow中发现了这个问题 ，解决方案通过在Eureka服务器配置中使用enableSelfPreservation:false 。 一段时间以后，这样做会使被杀的服务像预期的那样消失。 
 
 但是我可以看到以下消息： 
 
 
 
 自动保存模式被关闭，此时可能不会在网络/其他问题的情况下保护实时。 
 
 
 1.自我保护的目的是什么？ 该文档指出，对“客户端可以获取不再存在的实例”进行自我保护。 那么什么时候可以开/关？ 
 
 此外，当自我保存开启时，您可能会在Eureka服务器控制台警告中收到一个很好的信息： 
 
 
 
 紧急！ EUREKA可能不正当地要求他们在他们没有的情况下。 重新获得的利润低于此价格，并且这个价格不会过期，只能安全。 
 
 
 现在，继续使用Spring Eureka控制台。 
 
Lease expiration enabled    true/false
Renews threshold    5
Renews (last min)   4
 
 我遇到了一个奇怪的阈值行为：当我单独启动Eureka服务器时，阈值为1。 
 
 2.我有一个单一的Eureka服务器，并配置了registerWithEureka: false以防止在另一个服务器上注册。 那么为什么它出现在门槛数？ 
 
 3.对于每个客户端，我开始阈值增加+2。 我猜是因为他们每分钟发送2条续订邮件，对不对？ 
 
 尤里卡服务器永远不会发送更新，所以最后一分钟更新始终低于阈值。 这是正常吗？ 
 
renew threshold 5
rewnews last min: (client1) +2 + (client2) +2 -> 4
 
 服务器cfg： 
 
server:
  port: ${PORT:8761}

eureka:
  instance:
    hostname: localhost
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
  server:
    enableSelfPreservation: false
#   waitTimeInMsWhenSyncEmpty: 0
 
 客户1 cfg： 
 
spring:
  application:
    name: random-image-microservice

server:
  port: 9999

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
    healthcheck:
      enabled: true

I am new to developing microservices, although I have been researching about it for a while, reading both Spring's docs and Netflix's.
 
I have started a simple project available on Github. It is basically a Eureka server (Archimedes) and three Eureka client microservices (one public API and two private). Check github's readme for a detailed description.
 
The point is that when everything is running I would like that if one of the private microservices is killed, the Eureka server realizes and removes it from the registry.
 
I found this question on Stackoverflow, and the solution passes by using enableSelfPreservation:false in the Eureka Server config. Doing this after a while the killed service disappears as expected.
 
However I can see the following message:
 
 
 
THE SELF PRESERVATION MODE IS TURNED OFF.THIS MAY NOT PROTECT INSTANCE EXPIRY IN CASE OF NETWORK/OTHER PROBLEMS.
 
 
1. What is the purpose of the self preservation? The doc states that with self preservation on "clients can get the instances that do not exist anymore". So when is it advisable to have it on/off?
 
Furthermore, when self preservation is on, you may get an outstanding message in the Eureka Server console warning:
 
 
 
EMERGENCY! EUREKA MAY BE INCORRECTLY CLAIMING INSTANCES ARE UP WHEN THEY'RE NOT. RENEWALS ARE LESSER THAN THRESHOLD AND HENCE THE INSTANCES ARE NOT BEING EXPIRED JUST TO BE SAFE.
 
 
Now, going on with the Spring Eureka Console.
 
Lease expiration enabled    true/false
Renews threshold    5
Renews (last min)   4
 
I have come across a weird behaviour of the threshold count: when I start the Eureka Server alone, the threshold is 1.
 
2. I have a single Eureka server and is configured with registerWithEureka: false to prevent it from registering on another server. Then, why does it show up in the threshold count?
 
3. For every client I start the threshold count increases by +2. I guess it is because they send 2 renew messages per min, am I right?
 
4. The Eureka server never sends a renew so the last min renews is always below the threshold. Is this normal?
 
renew threshold 5
rewnews last min: (client1) +2 + (client2) +2 -> 4
 
Server cfg:
 
server:
  port: ${PORT:8761}

eureka:
  instance:
    hostname: localhost
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
  server:
    enableSelfPreservation: false
#   waitTimeInMsWhenSyncEmpty: 0
 
Client 1 cfg:
 
spring:
  application:
    name: random-image-microservice

server:
  port: 9999

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
    healthcheck:
      enabled: true

原文：https://stackoverflow.com/questions/33921557