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Spring Boot Eureka Demo

Simple demo of service registration and discovery using Eureka.

Initial work based on this guide:

https://spring.io/guides/gs/service-registration-and-discovery/

Try it out

Eureka Server

Start the server

cd eureka-server
mvn spring-boot:run

Visit the Eureka dashboard at http://localhost:8761

Note that there are no 'Instances' yet registered

Eureka Client

Start up a client

cd eureka-client
mvn spring-boot:run

Visit the client directly at http://localhost:8080/

The /whoami endpoint will show the client's self-knowledge of its application name and port

{
  "springApplicationName":"eureka-client",
  "serverPort":"8080"
}

The /instances endpoint will take up to a minute to update, but should eventually show all the instances of eureka-client that have been registered with the Eureka Discovery Client.

[
  {
    "host":"hostname",
    "port":8080,
    "serviceId":"EUREKA-CLIENT",
    "uri":"http://hostname:8080",
    "secure":false
  }
]

You can also visit the Eureka dashoboard again now and see it listed there.

Spin up another client with a different name

You can see that another client will be registred by doing the following:

cd eureka-client
mvn spring-boot:run -Dspring.application.name=foo -Dserver.port=8081

The /whoami endpoint will show the name foo and the port 8081.

In a minute or so, the /instances endpoint will show the information about this foo instance too.

On the Eureka dashboard, two clients will now be registered.

Spin up another client with the same name

Now try spinning up another instance of eureka-client by only over-riding the port parameter:

By default, Eureka uses the hostname as the instance name, so you have to override the eureka.instance.metadataMap.instanceId parameter when running two instances locally for testing. (reference)

cd eureka-client
mvn spring-boot:run -Dserver.port=8082 -Deureka.instance.metadataMap.instanceId=instance2

The /whoami endpoint for http://localhost:8082 shows what we expect.

In a minute or so, the /instances endpoint now shows two instances of eureka-client running.

The Eureka dashboard also shows 2 instances of eureka-client running.

Access eureka-client service via the zuul proxy

Start up the zuul proxy application

cd zuul-proxy
mvn spring-boot:run

The proxy automatically maps a route based on the service names it finds in the eureka registry and uses client side load balancing.

Repeated requests to http://localhost:9999/eureka-client/whoami will show a different port depending on which instance it calls.