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Microservices - Service Registration/ discovery using Spring boot and Eureka

In this tutorial we will learn how to create registry/ discovery server using Eureka and Spring boot. We will register our Rest microservice with this registry server which can be discovered by client by connecting to registry server.

What is registry/ discovery server

We can assume registry or discovery server as a central place where we can find all our microservices using their registered IDs with discovery server. Microservices register themselves in registry server and client applications access them using a single registry or discovery server. It is similar to a phone directory but provides many other useful features.
If we don't user registry server then we need host name and endpoint details to access a service. In today's era most of the services are deployed in cloud and using cloud features like auto-scaling where network addresses are updated dynamically and we can't use a simple network address for that. Now when we use registry server, then such microservice are registering themselves with registry server. And since clients are access these services using registry server they don't need to bother of network address. They just need to connect to registry server and invoke the desired operations using registered service ID.

Creating registry/ discovery server

In below steps we will see the implementation to create our registry server.
  • Maven dependencies
  •         <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            </dependency>
    
  • Enable Eureka server on main class
  • @EnableEurekaServer
    @SpringBootApplication
    public class DiscoveryServerApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(DiscoveryServerApplication.class, args);
        }
    
    }
    
  • Required configuration 
  • spring.application.name: discovery-server
    server.port: 8089
    eureka:
      instance:
        hostname: localhost
      client:
        registerWithEureka: false
        fetchRegistry: false
    

Service registration

Here I am using spring boot microservice to register with our discovery server. Below are the steps to register a service.
  • Maven dependencies
  •         <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
    
  • Enable discovery client
  • @EnableDiscoveryClient
    @SpringBootApplication
    public class UserMgmtServiceApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(UserMgmtServiceApplication.class, args);
        }
    }
    
  • Required configuration
  • eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:8089/eureka
    

Microservice (User management)

This microservice is created for demonstration purpose. This service uses spring cloud config and mongo DB which will be required to run this microservice but you can create your own code without these dependencies. Below is the POST link for complete tutorial and source code.

Accessing Eureka server dashboard

Now start registry server by executing below command.
mvn spring-boot:run
Access below URL in browser and you will see the similar screen as given below. Currently there no services registered.
URL: http://localhost:8089/
Eureka server

Now start the microservice and refresh the discovery service URL. In below screen you can see now it is showing the service instance as registered applications.
eureka server

Source code

Source code is available at below Git location.
https://github.com/thetechnojournals/microservices/tree/master/discovery-server

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