Cloud Consul Discovery

https://github.com/spring-boot-tutorials/cloud-consul-discovery

Install & Run Consul Server

docker run \
  --name consul-server \
  -p 8500:8500 \
  -p 8600:8600/udp \
  hashicorp/consul \
  agent -server \
  -bootstrap-expect=1 \
  -ui -client=0.0.0.0

Create Initial Code Base

• Go to https://start.spring.io/

• Add the following dependencies: - spring-boot-starter-web - spring-cloud-starter-consul-discovery - lombok

• Click Generate

Dependencies

Dependencies used in pom.xml:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-consul-discovery</artifactId>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
</dependency>

Properties

Add the following properties into src/main/resources/application.yaml:

spring:
  application:
    name: myApp
  cloud:
    consul:
      host: localhost
      port: 8500
      discovery:
        instanceId: ${spring.application.name}:${random.value}
#        uncomment to disable service discovery
#        enabled: false
        healthCheckPath: /my-health-check
        healthCheckInterval: 20s

Model

Create new file src/main/java/com/example/consul/discovery/MyDiscoveryConfiguration.java:

@EnableDiscoveryClient
public class MyDiscoveryConfiguration {
}

Controller

Create a new file src/main/java/com/example/consul/discovery/MyDiscoveryController.java:

@RestController
@RequiredArgsConstructor
public class MyDiscoveryController {

    private final DiscoveryClient discoveryClient;

    @GetMapping("/ping")
    public String ping() {
        return "pong";
    }

    @GetMapping("/discoveryClient")
    public String discoveryPing() throws RestClientException, ServiceUnavailableException {
        URI service = serviceUrl()
                .map(s -> s.resolve("/ping"))
                .orElseThrow(ServiceUnavailableException::new);
        return new RestTemplate().getForEntity(service, String.class)
                .getBody();
    }

    private Optional<URI> serviceUrl() {
        return discoveryClient.getInstances("myApp")
                .stream()
                .findFirst()
                .map(ServiceInstance::getUri);
    }
}

Create another file src/main/java/com/example/consul/discovery/MyHealthCheckController.java:

@RestController
public class MyHealthCheckController {

    @GetMapping("/my-health-check")
    public String healthCheck() {
        return "good";
    }
}

Run Spring Application

Open terminal at project root and execute the following:

mvn spring-boot:run

Go to http://localhost:8500 and verify myApp was registered.