Apache Zookeeper is a distributed coordination service for distributed systems. It is used to manage large distributed systems. Spring Boot is a popular Java framework for developing microservices.
In this post, we will learn how to integrate Spring Boot with Apache Zookeeper. We will use Zookeeper to coordinate and synchronize our Spring Boot microservices.
Before we can start using Zookeeper, we need to install it. We can install Zookeeper using Homebrew on macOS:
$ brew install zookeeper
Or we can download the Zookeeper binary release from the Apache Zookeeper website.
Once Zookeeper is installed, we can start it using the following command:
$ zookeeper-server-start /usr/local/etc/kafka/zookeeper.properties
We can create a Spring Boot project using the Spring Initializr. We will use the following dependencies:
We need to configure our Spring Boot application to use Zookeeper. We can do this by adding the following properties to our application.properties
file:
spring.cloud.zookeeper.connect-string=localhost:2181
spring.cloud.zookeeper.discovery.instance-id=${spring.application.name}
spring.cloud.zookeeper.discovery.root=/${spring.application.name}
spring.cloud.zookeeper.discovery.service-name=${spring.application.name}
spring.cloud.zookeeper.discovery.enabled=true
We can create a Spring Boot service using the @SpringBootApplication
annotation:
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
We can add a Rest controller to our service using the @RestController
annotation:
@RestController
public class GreetingController {
@GetMapping("/greeting")
public String greeting() {
return "Hello, world!";
}
}
We can test our service by sending a GET
request to the /greeting
endpoint:
$ curl localhost:8080/greeting
Hello, world!
Once our service is up and running, we need to register it with Zookeeper. We can do this using the @DiscoveryClient
annotation:
@SpringBootApplication
@DiscoveryClient
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
Once our service is registered with Zookeeper, we can access it from another service. We can do this by injecting a DiscoveryClient
into our controller:
@RestController
public class GreetingController {
@Autowired
private DiscoveryClient discoveryClient;
@GetMapping("/greeting")
public String greeting() {
List<ServiceInstance> instances = discoveryClient.getInstances("greeting-service");
if (instances.isEmpty()) {
return "Hello, world!";
}
String url = instances.get(0).getUri().toString();
return "Hello, world! (from " + url + ")";
}
}
In this post, we learned how to integrate Spring Boot with Apache Zookeeper. We used Zookeeper to coordinate and synchronize our Spring Boot microservices.