搭建一个简单的Eureka集群

现在我们稍微把上一篇文章中的Eureka应用扩展一下，扩展成一个简单的Eureka集群。架构图如下所示：

集群部署图

我们要部署两台Eureka服务器，两台ServiceProvider。为此，首先要修改本机的Hosts文件，以便在一台机子上模拟出多台的效果。

修改hosts文件

Eureka Server端

新建maven项目first-cloud-server，其pom依赖如下：

<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka-server</artifactId>
        </dependency>
    </dependencies>

我们通过启动时指定启动哪个server，server1还是server2.这就需要在配置文件中配置不同的profile。

启动类如下所示，启动时需要从输入中读取需要启动的server（server1或server2）

@SpringBootApplication
@EnableEurekaServer
public class FirstCloudServer {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String profiles = scanner.nextLine();
        new SpringApplicationBuilder(FirstCloudServer.class).profiles(profiles).run(args);
    }
}

配置文件如下所示：

server:
  port: 8761
spring:
  application:
    name: first-cloud-server
  profiles: server1
eureka:
  instance:
    hostname: server1
  client:
    serverUrl:
      defaultZone: http://server2:8762/eureka/

---
server:
  port: 8762
spring:
  application:
    name: first-cloud-server
  profiles: server2
eureka:
  instance:
    hostname: server2
  client:
    serverUrl:
      defaultZone: http://server1:8761/eureka/

配置文件中通过profiles声明了两套server配置。它们在启动完之后，会互相注册

Eureka provider

新建Maven项目first-cloud-provider，其pom文件的依赖如下所示：

<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
    </dependencies>

因为我们也是需要启动两台Provider，就通过启动的时候指定不同的端口实现。启动类如下：

@SpringBootApplication
@EnableEurekaClient
public class FirstCloudServiceProvider {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String port = scanner.nextLine();
        new SpringApplicationBuilder(FirstCloudServiceProvider.class).properties("server.port=" + port).run(args);
    }
}

启动完成之后，分别向两台Eureka Server注册，配置文件如下：

spring:
  application:
    name: first-cloud-provider
eureka:
  instance:
    hostname: localhost
  client:
    serviceUrl:
      defaultZone: http://server1:8761/eureka/,http://server2:8762/eureka/

我们还是对外提供了一个REST服务，代码如下：

@RestController
public class FirstCloudController {

    @RequestMapping(value = "/person/{personId}", method = RequestMethod.GET,
            produces = MediaType.APPLICATION_JSON_VALUE)
    public Person findPerson(@PathVariable("personId") Integer personId, HttpServletRequest request) {
        Person person = new Person(personId, "Crazyit", 30);
        person.setMessage(request.getRequestURL().toString());
        return person;
    }
}

与之前单机部署不同的是，这次在返回中添加了请求的URL信息。

Person Bean如下：

public class Person {

    private Integer id;

    private String name;

    private Integer age;

    private String message;

    public Person() {
        super();
    }

    public Person(Integer id, String name, Integer age) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

Eureka Invoker

同样地，创建first-cloud-invoker maven项目，其pom依赖为：

<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
        </dependency>
    </dependencies>

修改其配置文件，使其在启动之后向两个Eureka Server注册：

server:
  port: 9000
spring:
  application:
    name: first-cloud-invoker
eureka:
  instance:
    hostname: localhost
  client:
    serviceUrl:
      defaultZone: http://server1:8761/eureka/,http://server2:8762/eureka/

同样地，提供一个对外的REST接口，供调用方调用

@RestController
@Configuration
public class InvokerController {

    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }

    @RequestMapping(value = "/router", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
    public String router() {
        RestTemplate template = getRestTemplate();
        String json = template.getForObject("http://first-cloud-provider/person/1", String.class);
        return json;
    }
}

启动类：

@SpringBootApplication
@EnableDiscoveryClient
public class FirstInvoker {

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

Rest Client

这边简易实现了一个客户端Rest Client，用来调用Invoker提供的rest接口，以检验provider的负载均衡能力。

它也是一个Maven项目，pom依赖为：

<dependencies>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.2</version>
        </dependency>
    </dependencies>

编写一个测试类，代码如下：

public static void main(String[] args) throws Exception {
        // 创建默认的HttpClient
        CloseableHttpClient httpclient = HttpClients.createDefault();
        // 调用6次服务并输出结果
        for(int i = 0; i < 6; i++) {
            // 调用 GET 方法请求服务
            HttpGet httpget = new HttpGet("http://localhost:9000/router");
            // 获取响应
            HttpResponse response = httpclient.execute(httpget);
            // 根据 响应解析出字符串
            System.out.println(EntityUtils.toString(response.getEntity()));
        }
    }

启动

按照

Eureka Server
Eureka provider
Eureka Invoker

的顺序启动。启动完成之后，可以看到Eureka Server1 和 Eureka Server2的注册信息。

Eureka Server1的注册信息

Eureka Server2的注册信息

最后，执行rest client，可以看到rest client 的输出为：

REST Client的输出

从输出中可以看出，Invoker在调用的时候，是调用端口12222一次，端口13333一次，然后又是端口12222一次的。说明Eureka 是做了负载均衡的。

接着再看下Invoker的日志：

2020-04-23 17:41:03.095  INFO 16484 --- [nio-9000-exec-1] c.n.l.DynamicServerListLoadBalancer      : DynamicServerListLoadBalancer for client first-cloud-provider initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=first-cloud-provider,current list of Servers=[localhost:13333, localhost:12222],Load balancer stats=Zone stats: {defaultzone=[Zone:defaultzone;	Instance count:2;	Active connections count: 0;	Circuit breaker tripped count: 0;	Active connections per server: 0.0;]
},Server stats: [[Server:localhost:12222;	Zone:defaultZone;	Total Requests:0;	Successive connection failure:0;	Total blackout seconds:0;	Last connection made:Thu Jan 01 08:00:00 CST 1970;	First connection made: Thu Jan 01 08:00:00 CST 1970;	Active Connections:0;	total failure count in last (1000) msecs:0;	average resp time:0.0;	90 percentile resp time:0.0;	95 percentile resp time:0.0;	min resp time:0.0;	max resp time:0.0;	stddev resp time:0.0]
, [Server:localhost:13333;	Zone:defaultZone;	Total Requests:0;	Successive connection failure:0;	Total blackout seconds:0;	Last connection made:Thu Jan 01 08:00:00 CST 1970;	First connection made: Thu Jan 01 08:00:00 CST 1970;	Active Connections:0;	total failure count in last (1000) msecs:0;	average resp time:0.0;	90 percentile resp time:0.0;	95 percentile resp time:0.0;	min resp time:0.0;	max resp time:0.0;	stddev resp time:0.0]
]}ServerList:org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList@304a4707

从日志中可以看出，Invoker从Server中获取了服务first-cloud-provider的服务列表，分别是localhost:12222和localhost:13333。

参考资料

疯狂Spring Cloud微服务架构实战