Microservice -Cloud Configurations -Spring

June 20, 2021

Let's explore the Microservice deployments ,registration using Service Registry and controlling the communication using APIGateways in next blog.
Will create a microservice Library using H2 databass fro the persistance.
The entire codebase will be shared in the git will share at the end of the blog.
Let's create the Books microservices like below
Controller
Services

Repository

Entity

application.yaml

server:

  port: 9000

Postman test output

Create the Books microservices the same way. Refer to the code from the end. Mail goal is to access using the gateway service

Big Step Going to add the microservices to the Service Registry

to do that create one more microservices with the below dependency

<dependencies>

   <dependency>

      <groupId>org.springframework.cloud</groupId>

      <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>

   </dependency>

   <dependency>

      <groupId>org.springframework.boot</groupId>

      <artifactId>spring-boot-starter-test</artifactId>

      <scope>test</scope>

   </dependency>

</dependencies>

and create application.yml with the values

server:

  port: 8761

eureka:

  client:

    register-with-eureka: false

    fetch-registry: false

where 8761 is the default port number usied for the serive resgistry can change if we want.

Currentmicro service is not registering to the service resigrty and not fetching from it so

keeping this properties to false.

Annotate the ServiceRegistryApplication class with @EnableEurekaServer

@SpringBootApplication
@EnableEurekaServerpublic class ServiceRegistryApplication {
   public static void main(String[] args) {      SpringApplication.run(ServiceRegistryApplication.class, args);   }

}

Yes, by doing this much our service Register is ready 💪.

Once the Service Registry is up will register the microservices to the registry.

Client configurations

Edit the pom to enable Eureka client

Configure application.yml like below

eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://localhost:8761/eureka
    instance:
      hostname: localhost

spring:
  application:
    name: LIBRARY-SERVICE

Annotate the main class with @EnableEurekaClient

After the successful configuration, we are ready for deployment, deploy applications in the order.

I created one more microservices like LIBRARY-SERVICES with the name BOOK-SERVICES.

First, run the ServiceRegistryApplication then the client microservice (Book and Library) where we configured the fetch-registry to true

The benefit of registering the application to the service registry is that we can use the application name ("LIBRARY-SERVICE") to make internal calls. No need to remember about the IP configurations 😉.

See the below example

Before Registering to the Service Registry used to call the application using the IP & port number.

After Registering to the Service Registry can use the Application name like below

Create API -gateway, Client will communicate through API gateway where we used to write all the routing, it's kind of abstraction.

API-Gateway also get registered into the service registry

To create one more service, like Book and Library only changes are in the routing config files

server:
  port: 9003

spring:
  application:
    name: API-GATEWAY
  cloud:
    gateway:
      discovery:
        locator:
          lower-case-service-id: true
          enabled: true
      routes:
        - id: LIBRARY-SERVICE
          uri: http://localhost:9000
          predicates:
          - Path=/library/**
          filters:
            - name: CircuitBreaker
              args:
                name: LIBRARY-SERVICE
                fallbackuri: forward:/libraryfallback
        - id: BOOK-SERVICE
          uri: http://localhost:9001
          predicates:
          - Path=/books/**