Service discovery in Java microservices architecture

Service discovery in Java microservices allows applications to dynamically discover and connect to other services. Eureka is a client/server system that provides service registration, discovery and load balancing. Spring Cloud Eureka is the Spring Cloud implementation of Eureka, providing automatic registration, load balancing and Spring integration. zkclient can also be used for service discovery, allowing applications to discover service addresses through Zookeeper.

Service discovery in Java microservice architecture

Introduction

In microservices In service architecture, service discovery is crucial because it allows applications to dynamically discover and connect to other services. There are several service discovery technologies in Java, and this article will explore some of them and provide practical examples.

Eureka

Eureka is an open source service discovery framework developed by Netflix. It is a client/server system where the Eureka server stores a service registry and the Eureka client periodically registers services with the server. Eureka provides the following functions:

• Service registration and deregistration
• Service discovery
• Load balancing

##Spring Cloud :

Spring Cloud Eureka is an implementation of Eureka in the Spring Cloud ecosystem, which provides an Eureka client that seamlessly integrates with Spring applications. It provides the following features:

Automatic service registration and deregistration
• Configurable load balancing strategies
• Integration with Spring Boot and Spring Cloud configuration properties

Practical case

Using Spring CloudEureka to discover services:

In the Maven pom.xml file Add Eureka dependency:

1. <dependency>
       <groupId>org.springframework.cloud</groupId>
       <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
       <version>3.1.0</version>
   </dependency>

Create Eureka service class:

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

Enable Eureka client through
3. @EnableEurekaClient annotation, And use @SpringBootApplication to mark the service class.
Start the application on the Eureka server and check whether the service is registered by calling the following endpoint:

##http://localhost:8761/eureka/apps/[ service-name]

Use zkclient to discover the service:

Add zkclient dependency in the Maven pom.xml file:

1. <dependency>
       <groupId>com.101tec</groupId>
       <artifactId>zkclient</artifactId>
       <version>0.11</version>
   </dependency>

Create a Zookeeper service discovery class:

2. import org.I0Itec.zkclient.ZkClient;
   import org.I0Itec.zkclient.serialize.SerializableSerializer;
   
   import java.util.*;
   
   public class ZkServiceDiscovery {
   
       private static final String ZOOKEEPER_ADDRESS = "localhost:2181";
       private static final int SESSION_TIMEOUT = 3000;
       private static final int CONNECTION_TIMEOUT = 3000;
   
       private ZkClient zkClient;
   
       public ZkServiceDiscovery() {
           zkClient = new ZkClient(ZOOKEEPER_ADDRESS, SESSION_TIMEOUT, CONNECTION_TIMEOUT, new SerializableSerializer());
       }
   
       public List<String> discoverServices(String serviceName) {
           List<String> servicePaths = zkClient.getChildren("/services/" + serviceName + "/instances");
           List<String> services = new ArrayList<>();
   
           for (String servicePath : servicePaths) {
               services.add(zkClient.readData("/services/" + serviceName + "/instances/" + servicePath));
           }
   
           return services;
       }
   
       public void close() {
           zkClient.close();
       }
   
   }

Use the

discoverServices()
3. method to discover services and obtain their addresses. When closing the service, call the
close()
4. method to release Zookeeper client resources.

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