如何使用jhipster-registry动态地将请求流量从旧服务器实例切换到新服务器实例？

Question

I use jhipster-registry for registry and manage microservice .And it based on Spring Cloud Netflix Eureka and Spring Cloud Config.

when I add new api and publish next version of a micro service , I need

1. start a new service instance
2. switch request traffic from old instance to the new one
3. remove / shut down old one

And I don't want to restart my gateway during these steps. Actually, I'm look a runtime dynamic routing method .

Answer 1

eureka

Unfortunately, this is not that easy, as Eureka favors availability over consistency, so it happens, that your service discovery consists of services, which are dead. A workaround I prefer to use with eurka is to set the MaxAutoRetries property higher for all application (what is easy, as JHipster Registry is a config server, so i share this for all), like

ribbon:
  ConnectTimeout: 3000
  ReadTimeout: 60000
  MaxAutoRetries: 10

so this at least make your request succeed after time during a deployment. You will suffer some latency, as the first tries will go ahead to the old service, which is timing out...but no restarts are needed and your new services get online approx. 3 - 5 minutes after deploy (this is my experience...it may differ from case to case)

consul

As an alternative you might consider to switch to Hashicorps consul instead of eureka, which favors consistency, so you will be able to manage and sync your service discovery as soon as you deploy.

Currently JHipster does only provide BETA support for consul, becaue it is not possible to run a fully secure installation, because of this bug where I am waiting for the review of the fix

Answer 2

It is actually easy to achieve what you want :

• Deploy two versions of your service with different instanceIds for example service-v1 and service-v2 . This is easy to achieve with setting eureka.instance.instanceId .

• Initialy your Zuul Gateway is is proxying requests to service-v1 with the following properties present in your config server's gateway.yml:

 zuul: routes: service: path: /service/** serviceId: service-v1 

• Change the config server zuul configuration to this:

 zuul: routes: service: path: /service/** serviceId: service-v2 

• Then trigger a refresh of the gateway's config:

 curl -X POST http://localhost:8080/management/refresh 

(note that this endpoint is secured so you will need to pass it a token to pass through)