Ribbon的負載均衡

前面的博客用Ribbon搭建了初步的例子，但是還沒實現真正的負載均衡，因爲只有一個生產者，要達到負載均衡效果需要先搞三個服務提供者形成集羣，然後才能演示負載均衡，以及負載均衡策略。本篇博客跟前面搭建Eureka集羣一樣，使用一個啓動類來跑三個yml配置不同的工程，以達到集羣的效果來演示負載均衡

參照microservice-student-provider-1001模塊重新建一個microservice-student-provider模塊

pom.xml如下：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.ue</groupId>
        <artifactId>microservice</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <artifactId>microservice-student-provider</artifactId>

    <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-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.10</version>
        </dependency>
        <!-- 修改後立即生效，熱部署 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>springloaded</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>
        <dependency>
            <groupId>com.ue</groupId>
            <artifactId>microservice-common</artifactId>
            <version>1.0-SNAPSHOT</version>
            <scope>compile</scope>
        </dependency>
        <!--添加註冊中心Eureka相關配置-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        <!-- actuator監控引入 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>
</project>

yml配置如下：

---
server:
  port: 1001
  context-path: /
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/demosite1?useUnicode=true&characterEncoding=utf8
    username: root
    password: root
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
  application:
    name: microservice-student
  profiles: provider-1001

eureka:
  instance:
    hostname: localhost
    appname: microservice-student
    instance-id: microservice-student:1001
    prefer-ip-address: true
  client:
    service-url:
      defaultZone: http://eureka2001.test.com:2001/eureka/,http://eureka2002.test.com:2002/eureka/,http://eureka2003.test.com:2003/eureka/

info:
  groupId: com.ue.microservice
  artifactId: microservice-student-provider-1001
  version: 1.0-SNAPSHOT
  負責人: Tom
  聯繫電話: 123456

---
server:
  port: 1002
  context-path: /
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/demosite1?useUnicode=true&characterEncoding=utf8
    username: root
    password: root
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
  application:
    name: microservice-student
  profiles: provider-1002

eureka:
  instance:
    hostname: localhost
    appname: microservice-student
    instance-id: microservice-student:1002
    prefer-ip-address: true
  client:
    service-url:
      defaultZone: http://eureka2001.test.com:2001/eureka/,http://eureka2002.test.com:2002/eureka/,http://eureka2003.test.com:2003/eureka/

info:
  groupId: com.ue.microservice
  artifactId: microservice-student-provider-1002
  version: 1.0-SNAPSHOT
  負責人: Tom
  聯繫電話: 123456

---
server:
  port: 1003
  context-path: /
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/demosite1?useUnicode=true&characterEncoding=utf8
    username: root
    password: root
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
  application:
    name: microservice-student
  profiles: provider-1003

eureka:
  instance:
    hostname: localhost
    appname: microservice-student
    instance-id: microservice-student:1003
    prefer-ip-address: true
  client:
    service-url:
      defaultZone: http://eureka2001.test.com:2001/eureka/,http://eureka2002.test.com:2002/eureka/,http://eureka2003.test.com:2003/eureka/

info:
  groupId: com.ue.microservice
  artifactId: microservice-student-provider-1003
  version: 1.0-SNAPSHOT
  負責人: Tom
  聯繫電話: 123456

啓動類代碼如下：

package com.ue;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@SpringBootApplication
@EntityScan("com.ue.entity")
@EnableJpaRepositories("com.ue.repository")
@EnableEurekaClient
public class MicroserviceStudentProviderApplication {

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

}

然後寫用來測試的接口：

@Value("${server.port}")
private String port;

@RequestMapping("/ribbon")
public String ribbon(){
    return "工號【"+port+"】正在爲您服務";
}

@RequestMapping("/ribbon")
public String ribbon(){
    return restTemplate.getForObject(PRE_HOST + "/student/ribbon", String.class);
}

然後用這個新建的項目的啓動類配置多個Run Configuration：

然後依次啓動兩個註冊中心、三個生產端、一個消費端：

然後在瀏覽器地址欄輸入http://eureka2001.test.com:2001，可看到服務提供者的註冊情況：

然後訪問http://localhost/student/list，多刷新幾次看頁面上顯示的內容，可輪詢看到訪問對應的服務提供者的端口：

但是這種默認的輪詢策略是不能滿足實際需求的，比如有3個服務提供者，如果突然掛了一個，這樣的話，默認輪詢時總有1/3的概率會訪問失敗，所以可以看下ribbon提供的策略還有哪些：

策略名	策略聲明	策略描述	實現說明
BestAvailableRule	public class BestAvailableRule extends ClientConfigEnabledRoundRobinRule	選擇一個最小的併發請求的server	逐個考察Server，如果Server被tripped了，則忽略，在選擇其中ActiveRequestsCount最小的server
AvailabilityFilteringRule	public class AvailabilityFilteringRule extends PredicateBasedRule	過濾掉那些因爲一直連接失敗的被標記爲circuit tripped的後端server，並過濾掉那些高併發的的後端server（active connections 超過配置的閾值）	使用一個AvailabilityPredicate來包含過濾server的邏輯，其實就就是檢查status裏記錄的各個server的運行狀態
WeightedResponseTimeRule	public class WeightedResponseTimeRule extends RoundRobinRule	根據響應時間分配一個weight，響應時間越長，weight越小，被選中的可能性越低	一個後臺線程定期的從status裏面讀取評價響應時間，爲每個server計算一個weight。Weight的計算也比較簡單responsetime 減去每個server自己平均的responsetime是server的權重。當剛開始運行，沒有形成status時，使用roubine策略選擇server。
RetryRule	public class RetryRule extends AbstractLoadBalancerRule	對選定的負載均衡策略機上重試機制	在一個配置時間段內當選擇server不成功，則一直嘗試使用subRule的方式選擇一個可用的server
RoundRobinRule	public class RoundRobinRule extends AbstractLoadBalancerRule	roundRobin方式輪詢選擇server	輪詢index，選擇index對應位置的server
RandomRule	public class RandomRule extends AbstractLoadBalancerRule	隨機選擇一個server	在index上隨機，選擇index對應位置的server
ZoneAvoidanceRule	public class ZoneAvoidanceRule extends PredicateBasedRule	複合判斷server所在區域的性能和server的可用性選擇server	使用ZoneAvoidancePredicate和AvailabilityPredicate來判斷是否選擇某個server，前一個判斷判定一個zone的運行性能是否可用，剔除不可用的zone（的所有server），AvailabilityPredicate用於過濾掉連接數過多的Server

使用這些策略的時候就在服務消費端SpringCloudConfig配置類中指定IRule實現接口即可，如使用RetryRule：

以上就是如何搭建一個生產端集羣並使用Ribbon進行負載均衡的全部內容，在消費端調用生產端時也由原來的根據生產者的IP+端口來調用改成了根據生產者在Eureka註冊中心註冊的應用名稱來調用