Nacos Discovery en

Spring Cloud Alibaba Nacos Discovery

Nacos is an easy-to-use dynamic service discovery, configuration and service management platform for building cloud native applications.

With Spring Cloud Alibaba Nacos Discovery, you can quickly access the Nacos service registration feature based on Spring Cloud’s programming model.

Service Registration/Discovery: Nacos Discovery

Service discovery is one of the key components in the microservices architecture. In such a architecture, configuring a service list for every client manually could be a daunting task, and makes dynamic scaling extremely difficult. Nacos Discovery helps you to register your service to the Nacos server automatically, and the Nacos server keeps track of the services and refreshes the service list dynamically. In addition, Nacos Discovery registers some of the metadata of the service instance, such as host, port, health check URL, homepage to Nacos. For details about how to download and start Nacos, refer to the Nacos Website.

How to Introduce Nacos Discovery for service registration/discovery

please use the starter with the group ID as com.alibaba.cloud and the artifact ID as spring-cloud-starter-alibaba-nacos-discovery.

<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>

An example of using Nacos Discovery for service registration/discovery and call

Nacos Discovery integrate with the Netflix Ribbon, RestTemplate or OpenFeign can be used for service-to-service calls.

Nacos Server Startup

For details about how to download and start Nacos, refer to the Nacos Website.

After Nacos Server starts, go to http://ip:8848 to view the console (default account name/password is nacos/nacos):

Figure 1. Nacos Dashboard

For more Nacos Server versions, you can download the latest version from release page.

Start a Provider Application

The following sample illustrates how to register a service to Nacos.

Configuration of pom.xml The following is a complete example of pom.xml:

<?xml version="1.0" encoding="UTF-8"? >
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>open.source.test</groupId>
    <artifactId>nacos-discovery-test</artifactId>
    <version>1.0-SNAPSHOT</version>
    <name>nacos-discovery-test</name>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>${spring.boot.version}</version>
        <relativePath/>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring.cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>${spring.cloud.alibaba.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

Configuration of application.properties Some of the basic configurations of Nacos must be included in application.properties(or application.yaml), as shown below： application.properties

server.port=8081
spring.application.name=nacos-producer
spring.cloud.nacos.discovery.server-addr=127.0.0.1:8848
management.endpoints.web.exposure.include=*

Note	If you do not want to use Nacos for service registration and discovery, you can set `spring.cloud.nacos.discovery` to `false`.

The following is a sample for starting Provider:

@SpringBootApplication
@EnableDiscoveryClient
public class NacosProviderDemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(NacosProducerDemoApplication.class, args);
    }

    @RestController
    public class EchoController {
        @GetMapping(value = "/echo/{string}")
        public String echo(@PathVariable String string) {
            return "Hello Nacos Discovery " + string;
        }
    }
}

Now you can see the registered services on the Nacos console.

Note	Before you start the provider application, please start Nacos first. Refer to Naco Website for more details.

Start a Consumer Application

It might not be as easy as starting a provider application, because the consumer needs to call the RESTful service of the provider. In this example, we will use the most primitive way, that is, combining the LoadBalanceClient and RestTemolate explicitly to access the RESTful service. You can refer to section 1.2 for pom.xml and application.properties configurations. The following is the sample code for starting a consumer application.

Note	You can also access the service by using RestTemplate and FeignClient with load balancing.

@SpringBootApplication
@EnableDiscoveryClient
public class NacosConsumerApp {

    @RestController
    public class NacosController{

        @Autowired
        private LoadBalancerClient loadBalancerClient;
        @Autowired
        private RestTemplate restTemplate;

        @Value("${spring.application.name}")
        private String appName;

        @GetMapping("/echo/app-name")
        public String echoAppName(){
            //Access through the combination of LoadBalanceClient and RestTemolate
            ServiceInstance serviceInstance = loadBalancerClient.choose("nacos-provider");
            String path = String.format("http://%s:%s/echo/%s",serviceInstance.getHost(),serviceInstance.getPort(),appName);
            System.out.println("request path:" +path);
            return restTemplate.getForObject(path,String.class);
        }

    }

    //Instantiate RestTemplate Instance
    @Bean
    public RestTemplate restTemplate(){

        return new RestTemplate();
    }

    public static void main(String[] args) {

        SpringApplication.run(NacosConsumerApp.class,args);
    }
}

In this example, we injected a LoadBalancerClient instance, and instantiated a RestTemplate manually. At the same time, we injected the configuration value of spring.application.name into the application, so that the current application name can be displayed when calling the service of the provider.

Note	Please start Nacos before you start the consumer application. For details, please refer to Nacos Website.

Next, access the http://ip:port/echo/app-name interface provided by the consumer. Here we started the port of 8082. The access result is shown below：

Address：http://127.0.0.1:8082/echo/app-name
Access result： Hello Nacos Discovery nacos-consumer