73. Service Discovery with Zookeeper

Service Discovery is one of the key tenets of a microservice based architecture. Trying to hand-configure each client or some form of convention can be difficult to do and can be brittle. Curator (A Java library for Zookeeper) provides Service Discovery through a Service Discovery Extension . Spring Cloud Zookeeper uses this extension for service registration and discovery.

73.1 Activating

Including a dependency on org.springframework.cloud:spring-cloud-starter-zookeeper-discovery enables autoconfiguration that sets up Spring Cloud Zookeeper Discovery.

For web functionality, you still need to include org.springframework.boot:spring-boot-starter-web .

When working with version 3.4 of Zookeeper you need to change the way you include the dependency as described here.

73.2 Registering with Zookeeper

When a client registers with Zookeeper, it provides metadata (such as host and port, ID, and name) about itself.

The following example shows a Zookeeper client:

public class Application {

    public String home() {
        return "Hello world";

    public static void main(String[] args) {
        new SpringApplicationBuilder(Application.class).web(true).run(args);


The preceding example is a normal Spring Boot application.

If Zookeeper is located somewhere other than localhost:2181 , the configuration must provide the location of the server, as shown in the following example:


      connect-string: localhost:2181

If you use Spring Cloud Zookeeper Config, the values shown in the preceding example need to be in bootstrap.yml instead of application.yml .

The default service name, instance ID, and port (taken from the Environment ) are ${spring.application.name} , the Spring Context ID, and ${server.port} , respectively.

Having spring-cloud-starter-zookeeper-discovery on the classpath makes the app into both a Zookeeper “service” (that is, it registers itself) and a “client” (that is, it can query Zookeeper to locate other services).

If you would like to disable the Zookeeper Discovery Client, you can set spring.cloud.zookeeper.discovery.enabled to false .

73.3 Using the DiscoveryClient

Spring Cloud has support for Feign (a REST client builder) and Spring RestTemplate , using logical service names instead of physical URLs.

You can also use the org.springframework.cloud.client.discovery.DiscoveryClient , which provides a simple API for discovery clients that is not specific to Netflix, as shown in the following example:

private DiscoveryClient discoveryClient;

public String serviceUrl() {
    List<ServiceInstance> list = discoveryClient.getInstances("STORES");
    if (list != null && list.size() > 0 ) {
        return list.get(0).getUri().toString();
    return null;