Spring cloud eureka feign ribbon

Ribbon提供一种客户端的负载均衡技术，实现和集群中的服务通信。包含了三种组件

Rule 一个逻辑组件用来确定从服务列表中获取哪一个服务
Ping 运行在后台的组件，用来确定服务是否可用
ServerList 一个后台线程，可以以特定的频率来刷新和过滤服务，可以是静态的也可以是动态的

这些组件既可以通过API方式设定，也可以在配置文件中设定在通过反射方式创建。

1.Common rules

RoundRobinRule 这个策略通过简单的轮询策略来选择服务，常常作为默认策略或者是高级策略的后备策略使用

AvailabilityFilteringRule 这个策略将跳过那些被认为路由断开的或者是高并发连接数的server instance

WeightedResponseTimeRule 这个策略通过利用服务的平均响应时间来得到一个权重，响应时间越长的权重越小，依据权重再随机的挑选一个策略

2.ServerList

Adhoc static server list 利用BaseLoadBalancer.setServersList()API设定一个静态的服务列表

ConfigurationBasedServerList 默认的ServerList实现方式，可以通过下面的方式设定

sample-client.ribbon.listOfServers=www.microsoft.com:80,www.yahoo.com:80,www.google.com:80

DiscoveryEnabledNIWSServerList 这中ServerList实现方式从 Eureka client中获取服务列表，在spring boot程序中，当Eureka相应的jar在classpath中存在，会默认采用这种策略

3.ServerListFilter
该组件是DynamicServerListLoadBalancer用来在ServerList过滤服务的组件，有以下两种实现方式

ZoneAffinityServerListFilter 过滤掉那些和client不在同一个zone的服务，除非client所在的zone中没有可用的server，通过以下方式可以启用

myclient.ribbon.EnableZoneAffinity=true

ServerListSubsetFilter 这个过滤器确保client只能访问到服务集合中的一个特定子集，并能周期性的不好用的服务替换掉，通过以下方式可以启用

myClient.ribbon.NIWSServerListClassName=com.netflix.niws.loadbalancer.DiscoveryEnabledNIWSServerList 
# the server must register itself with Eureka server with VipAddress "myservice"
myClient.ribbon.DeploymentContextBasedVipAddresses=myservice
myClient.ribbon.NIWSServerListFilterClassName=com.netflix.loadbalancer.ServerListSubsetFilter
# only show client 5 servers. default is 20.
myClient.ribbon.ServerListSubsetFilter.size=5

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 hello;

import java.util.Arrays;
import java.util.List;
import java.util.Random;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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;

@RestController
@EnableDiscoveryClient
@SpringBootApplication
public class SayHelloApplication {

  private static Logger log = LoggerFactory.getLogger(SayHelloApplication.class);

  @RequestMapping(value = "/greeting")
  public String greet() {
    log.info("Access /greeting");

    List<String> greetings = Arrays.asList("Hi there", "Greetings", "Salutations");
    Random rand = new Random();

    int randomNum = rand.nextInt(greetings.size());
    return greetings.get(randomNum);
  }

  public static void main(String[] args) {
    SpringApplication.run(SayHelloApplication.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>hello</groupId>
	<artifactId>say-hello</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>say-hello</name>
	<description>Demo project for Spring Boot</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>
	<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>

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

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

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

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

		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-eureka</artifactId>
		</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（因为在一台机器上模拟server cluster 所以用了三个profile 分别对应三个port）

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

---
spring:
  application:
    name: say-hello
  profiles: one
server:
  port: 8090

---
spring:
  application:
    name: say-hello
  profiles: two
server:
  port: 9092

---
spring:
  application:
    name: say-hello
  profiles: three
server:
  port: 9999

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、spring-cloud-starter-ribbon依赖，在启动类中加入@EnableFeignClients、@RibbonClient(name = "say-hello")注解

代码结构：

启动类

package hello;

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.cloud.netflix.ribbon.RibbonClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
@RibbonClient(name = "say-hello")
@EnableFeignClients
public class UserApplication {

	@Autowired
	HelloClient client;

	@RequestMapping("/greeting")
	public String hello() {
		return client.greet();
	}

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

	@FeignClient(name = "say-hello")
	interface HelloClient {
		@RequestMapping(value = "/greeting", method = GET)
		String greet();
	}
}

FeignClient、RibbonClient中的service id要和Eureka client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>hello</groupId>
	<artifactId>user</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>user</name>
	<description>Demo project for Spring Boot</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>

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

	<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/snapshot</url>
			<snapshots>
				<enabled>true</enabled>
			</snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>

</project>

应用配置信息

spring:
  application:
    name: user

server:
  port: 8888

say-hello:
  ribbon:
    ServerListRefreshInterval: 15000

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}}}

三、启动
按下面的顺序启动
Eureka server ->Eureka client（say-hello）-> user client(user)
其中Eureka client 启动时分别用
--spring.profiles.active=one
--spring.profiles.active=two
--spring.profiles.active=three
启动三个服务，注册到eureka中

等所有应用都启动后通过界面访问http://localhost:8888/greeting，可以正常访问Eureka client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 say-hello instance，因为我们注册到Eureka中的say-hello实例有三个，此处会利用Ribbon的RoundRobinRule规则获取一个实例，调用对应的greet()方法，返回调用结果给 user client，最终返回界面

Spring cloud eureka feign ribbon

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