A sample project to showcase how eureka can be used within microservice architecture to inter-service comunication, taking following features in consideration :
- Service-discovery
- Scalability
- Load balancing
Learned this stuff from https://cloud.spring.io/spring-cloud-netflix
All the modules are dockerized and the environment will be up in less then 30 sec. Keep playing by scaling up services and observe load balancing in the output.
Docker 17.X, docker-compose 14.X
It is requred to have a server which takes care of registering rest services and same can be used for discovery.
A sprng boot project which will run as a eureka server. Endpoint : http://localhost:8761/eureka
A spring boot project exposing an rest endpoint, which will display the name of the service(with which it will register itself with eureka for discvery) along with IP address of the system the service is hosted upon. Endpoint : http://[host-address]:8080/sysinfo
A spring boot project which will do following things :
a. Registers itself with eureka
b. Make use of rest client (Spring restTemplate) to call spring-rest-service-a using Eureka to resolve the address by service-name (Keeping in mind that multiple instances of this service is running)
Endpoint :
| Path | Descrioption |
|---|---|
| /sysInfo | curent service name with which it has registered itself with eureka |
| /stackInfo | ServiceName + /sysinfo of spring-rest-service-a |
Under development, look at it if need to see the native way of calling rest services using Eureka-client.
mvn clean install
It will create the respective spring boot jar and as well as docker images for the respoective projects. Verify the docker images by ''docker images` command.
navigate to root of the parent project and do a
docker-compose up -d
It will launch all the containers(Eureka server as well as the rest service modules).
Verify if all the containers are up and running using command docker ps
Open browser to check this url : http://localhost:8761/eureka
The registered services will be visible in the eureka UI.
Click on the services to see the endpoints are wokring(you need to modify the url though).
From Eureka UI, click on the spring-rest-service-b url, A url (with resolved IP and port for service-b) will open up in a new tab with /info, update the URL to call /stackInfo instead.
go back to your terminal and scale up spring-rest-service-a to run on 3 or may be 4 instances.
docker-compose scale rest-service-a=3
rest-service-a is the alias for spring-rest-service-a check docker-compose.yml file for all the aliases. while the instances are getting up, keep refreshing the /stackInfo output and keep a watch on ip address of spring-rest-service-a (Load balancing). Once all three instances are up and running, It will be visible in the Eureka Service UI as well.
- Highly available eureka server
- using different rest client for e.g Fiegn