在微服务架构中服务发现是一个非常核心的功能。在spring cloud中可以很方便集成Netflix Service Discovery组件eureka。Eureka包含server和client,其中server端能够以群集的形式提供,各个sever又可以通过同步其他server中注册的service状态来实现高可用性。
当一个Eureka client向server注册时,会提供自身的元数据信息,包括host、port、health check URI等信息,Eureka server通过侦听同一个service的不同实例的心跳信息来确定当前实例是否正常,如果心跳信息失败,就会自动将该实例移除。
调用注册到Eureka中的服务,可以不直接采用EurekaClient,利用声明式的rest client :feign,或者Spring RestTemplate可以更加方便的调用注册在Eureka总的服务。
二、例子
package hello; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer; @EnableEurekaServer @SpringBootApplication public class EurekaServiceApplication { public static void main(String[] args) { SpringApplication.run(EurekaServiceApplication.class, args); } }
<?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>com.example</groupId> <artifactId>eureka-service</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.1.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka-server</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>Camden.SR5</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> <repositories> <repository> <id>spring-snapshots</id> <name>Spring Snapshots</name> <url>https://repo.spring.io/libs-snapshot</url> <snapshots> <enabled>true</enabled> </snapshots> </repository> </repositories> </project>
server.port=8761 eureka.client.register-with-eureka=false eureka.client.fetch-registry=false logging.level.com.netflix.eureka=OFF logging.level.com.netflix.discovery=OFF
package demo; import java.util.Arrays; import java.util.List; import java.util.Random; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; /** * @author Spencer Gibb */ @SpringBootApplication @EnableDiscoveryClient @RestController public class HelloServerApplication { @RequestMapping("/greeting") public String hello() { List<String> greeting = Arrays.asList("Hi there","Greetings","Salutations"); Random rand = new Random(); int randomNum = rand.nextInt(greeting.size()); return greeting.get(randomNum); } public static void main(String[] args) { SpringApplication.run(HelloServerApplication.class, args); } }
<?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>org.test</groupId> <artifactId>feign-eureka-hello-server</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>feign-eureka-hello-server</name> <description>Demo project for Spring Cloud</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.1.RELEASE</version> <relativePath /> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <java.version>1.8</java.version> </properties> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>Camden.SR5</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>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-feign</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
spring: application: name: HelloServer server: port: 7111 eureka: client: serviceUrl: defaultZone: http://localhost:8761/eureka/ instance: leaseRenewalIntervalInSeconds: 10 metadataMap: instanceId: ${vcap.application.instance_id:${spring.application.name}:${spring.application.instance_id:${server.port}}}
package demo; import static org.springframework.web.bind.annotation.RequestMethod.GET; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.feign.EnableFeignClients; import org.springframework.cloud.netflix.feign.FeignClient; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; /** * @author Spencer Gibb */ @SpringBootApplication @RestController @EnableFeignClients public class HelloClientApplication { @Autowired HelloClient client; @RequestMapping("/greeting") public String hello() { return client.hello(); } public static void main(String[] args) { SpringApplication.run(HelloClientApplication.class, args); } @FeignClient("HelloServer") interface HelloClient { @RequestMapping(value = "/greeting", method = GET) String hello(); } }
FeignClient中的service id要和User server配置信息中的spring.application.name的值保持一致
<?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>org.test</groupId> <artifactId>feign-eureka-hello-client</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>feign-eureka-hello-client</name> <description>Demo project for Spring Cloud</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.1.RELEASE</version> <relativePath /> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <java.version>1.8</java.version> </properties> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>Camden.SR5</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>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-feign</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
spring: application: name: HelloClient server: port: 7211 eureka: client: serviceUrl: defaultZone: http://localhost:8761/eureka/ instance: leaseRenewalIntervalInSeconds: 10 metadataMap: instanceId: ${vcap.application.instance_id:${spring.application.name}:${spring.application.instance_id:${server.port}}} endpoints: restart: enabled: true shutdown: enabled: true health: sensitive: false
三、启动
按下面的顺序启动
Eureka server ->user server -> user client
等所有应用都启动后通过界面访问http://localhost:7211/greeting,可以正常访问user-server中的方法返回值,整个流程是 界面访问 user client 工程中的hello方法,user client通过@FeignClient中指定的service id从Eureka server中获取到注册的 HelloServer instance,即 user server,然后调用user server中的hello方法,返回调用结果给 user client,最终返回界面
四、Eureka 集群
1.修改Eureka-server对应的配置文件
spring: application: name: eureka-server-clustered profiles: primary server: port: 8011 eureka: instance: hostname: eureka-primary client: registerWithEureka: false fetchRegistry: false serviceUrl: defaultZone: http://eureka-secondary:8012/eureka/,http://eureka-tertiary:8013/eureka/ --- spring: application: name: eureka-server-clustered profiles: secondary server: port: 8012 eureka: instance: hostname: eureka-secondary client: registerWithEureka: false fetchRegistry: false serviceUrl: defaultZone: http://eureka-tertiary:8013/eureka/,http://eureka-primary:8011/eureka/ --- spring: application: name: eureka-server-clustered profiles: tertiary server: port: 8013 eureka: instance: hostname: eureka-tertiary client: registerWithEureka: false fetchRegistry: false serviceUrl: defaultZone: http://eureka-primary:8011/eureka/,http://eureka-secondary:8012/eureka/
2.修改user-server对应的配置文件
spring: application: name: UserServer server: port: 7111 eureka: client: serviceUrl: defaultZone: http://eureka-secondary:8012/eureka/ instance: leaseRenewalIntervalInSeconds: 10 metadataMap: instanceId: ${vcap.application.instance_id:${spring.application.name}:${spring.application.instance_id:${server.port}}}
注意:application.name 修改过,feignclient对应的serviceid也需要修改
3.修改user-client对应的配置文件
spring: application: name: UserClient server: port: 7211 eureka: client: serviceUrl: defaultZone: http://eureka-primary:8011/eureka/,http://eureka-secondary:8012/eureka/,http://eureka-tertiary:8013/eureka/ instance: leaseRenewalIntervalInSeconds: 10 metadataMap: instanceId: ${vcap.application.instance_id:${spring.application.name}:${spring.application.instance_id:${server.port}}} endpoints: restart: enabled: true shutdown: enabled: true health: sensitive: false
3.如果在同一台机器上,修改hosts
# 127.0.0.1 localhost # ::1 localhost 127.0.0.1 localhost 127.0.0.1 eureka-primary 127.0.0.1 eureka-secondary 127.0.0.1 eureka-tertiary
依次启动 Eureka-server user-server user-client,其中启动Eureka-server时用
java -jar eureka-server-clustered-0.0.1-SNAPSHOT.jar --spring.profiles.active=primary java -jar eureka-server-clustered-0.0.1-SNAPSHOT.jar --spring.profiles.active=secondary java -jar eureka-server-clustered-0.0.1-SNAPSHOT.jar --spring.profiles.active=tertiary
启动三次,此时Eureka-server以集群形式提供服务,可以关闭任意一个或两个来测试Eureka的高可用性