Spring Cloud使用ribbon實現負載均衡

Ribbon是什麼？

Ribbon是Netflix發佈的開源項目，主要功能是提供客戶端的軟件負載均衡算法，將Netflix的中間層服務連接在一起。Ribbon客戶端組件提供一系列完善的配置項如連接超時，重試等。也可以使用Ribbon實現自定義的負載均衡算法。

Spring Cloud使用Ribbon實現負載均衡

Ribbon默認使用輪詢來實現負載均衡，也就是如果我們將同一個服務部署在A和B機器上，那麼第一次請求將到A，第二次請求將到B

1.創建Eureka Server

創建一個Spring Boot工程eureka-server

注意Spring Boot與Spring Cloud版本必須對應，否則會報錯。
[查看版本信息]https://spring.io/projects/spring-cloud
pom.xml

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.dfyang</groupId>
    <artifactId>eureka-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-server</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Greenwich.RELEASE</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>
</project>

application.yml

server:
  port: 8761
spring:
  application:
    name: eureka-server
eureka:
  client:
    # 是否將自己註冊到Eureka Server，由於當前應用爲Eureka Service，故爲false
    register-with-eureka: false
    # 是否從Eureka Server獲取註冊信息，由於是單點，所以爲false
    fetch-registry: false
    # 與Eureka Server交互的地址，默認是http://localhost:8761/eureka
    service-url:
      default-zone: http://localhost:8761/eureka/

在啓動類上加上@EnableEurekaServer註解，表明是一個Eureka Server

package com.dfyang;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

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

}

啓動項目，訪問localhost:8761

2.創建第一個服務提供者service-producer

創建一個Spring Boot工程service-producer

pom.xml

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.dfyang</groupId>
    <artifactId>service-producer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>service-producer</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</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-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Greenwich.RELEASE</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>
</project>

application.yml

server:
  port: 8080
spring:
  application:
    name: service-producer
eureka:
  client:
    service-url:
      default-zone: http://localhost:8761/eureka/

啓動類上加上@EnableEurekaClient，表明是一個Eureka Client。
每個服務提供者也能作爲服務消費者消費服務

package com.dfyang;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
public class ServiceProducerApplication {

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

}

編寫接口

package com.dfyang.serviceProducer.Controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ProducerController {
    @RequestMapping("/service")
    public String service() {
        return "服務A";
    }
}

啓動服務，輸入localhost:8761

3.創建第二個服務提供者service-producer1

創建另一個一個Spring Boot工程service-producer1

要修改的只有兩個地方，端口號和接口(爲了展示區別)

application.yml

server:
  port: 8081
spring:
  application:
    name: service-producer
eureka:
  client:
    service-url:
      default-zone: http://localhost:8761/eureka/

編寫接口

package com.dfyang.serviceProducer.Controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ProducerController {
    @RequestMapping("/service")
    public String service() {
        return "服務B";
    }
}

啓動服務，輸入localhost:8761

4.創建服務消費者service-consumer(eureka client)

創建一個Spring Boot工程service-consumer

pom.xml

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.dfyang</groupId>
    <artifactId>service-consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>service-consumer</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</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-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Greenwich.RELEASE</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>
</project>

application.yml

server:
  port: 8082
spring:
  application:
    name: service-consumer
eureka:
  client:
    service-url:
      default-zone: http://localhost:8761/eureka/

在啓動類似加上@EnableDiscoveryClient（該註解與@EnableEurekaClient均表明是一個Eureka客戶端，但@EnableEurekaClient只能在Eureka使用）

package com.dfyang;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
public class ServiceConsumerApplication {

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

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

消費者獲取服務

package com.dfyang.serviceConsumer.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class ConsumerController {

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/consume")
    public String consume() {
        return restTemplate.getForObject("http://service-producer/service", String.class);
    }
}

輸入localhost:8761

輸入http://localhost:8082/consume
我們會看到服務A與服務B在交替執行

使用Ribbon的其他負載均衡策略

隨機
只需修改消費端程序入口

package com.dfyang;

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
public class ServiceConsumerApplication {

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

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

    @Bean
    public IRule ribbonRule() {
        return new RandomRule();
    }

}

BestAvailableRule
選擇一個最小的併發請求的server
AvailabilityFilteringRule
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
WeightedResponseTimeRule
根據相應時間分配一個weight，相應時間越長，weight越小，被選中的可能性越低。
RetryRule
對選定的負載均衡策略機上重試機制。
RoundRobinRule
輪詢調度
RandomRule
隨機選擇一個server
ZoneAvoidanceRule
複合判斷server所在區域的性能和server的可用性選擇server

Spring Cloud使用ribbon實現負載均衡

Ribbon是什麼？

Spring Cloud使用Ribbon實現負載均衡

1.創建Eureka Server

2.創建第一個服務提供者service-producer

3.創建第二個服務提供者service-producer1

4.創建服務消費者service-consumer(eureka client)

使用Ribbon的其他負載均衡策略

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