Spring cloud eureka feign

企业开发 2018-05-09 19:01:07 阅读次数: 2
一、简介
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
  • 1. Eureka server
    • 核心是在正常的Spring boot程序中加入spring-cloud-starter-eureka-server依赖，在启动类中加入@EnableEurekaServer 注解
  • 代码结构：


  • 启动类 
    • 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);
    }
}

  • pom文件 
    • <?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>

  • 应用配置信息 
    • 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

  • 2.Eureka client（即user server端）
    • 核心是在正常的Spring boot程序中加入spring-cloud-starter-eureka依赖，在启动类中加入@EnableDiscoveryClient注解
  • 代码结构：

  • 启动类 
    • 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);
	}
}

  • pom文件 
    • <?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>

  • 应用配置信息 
    • 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}}}

  • 3.User client（调用注册到Eureka server中的Eureka client）
    • 核心是在正常的Spring boot程序中加入spring-cloud-starter-eureka、spring-cloud-starter-feign依赖，在启动类中加入@EnableFeignClients注解
  • 代码结构：


  • 启动类 
    • 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

  • pom文件 
    • <?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>

  • 应用配置信息 
    • 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
  • primary


  • secondary

  • tertiary

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