在上一篇文章,講了服務的註冊和發現。在微服務架構中,業務都會被拆分成一個獨立的服務,服務與服務的通訊是基於http restful的。Spring cloud有兩種服務調用方式,一種是ribbon+restTemplate,另一種是feign。在這一篇文章首先講解下基於ribbon+rest。
一、ribbon簡介
Ribbon is a client side load balancer which gives you a lot of control over the behaviour of HTTP and TCP clients. Feign already uses Ribbon, so if you are using @FeignClient then this section also applies.
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ribbon是一個負載均衡客戶端,可以很好的控制htt和tcp的一些行爲。Feign默認集成了ribbon。
ribbon 已經默認實現了這些配置bean:
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IClientConfig ribbonClientConfig: DefaultClientConfigImpl
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IRule ribbonRule: ZoneAvoidanceRule
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IPing ribbonPing: NoOpPing
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ServerList ribbonServerList: ConfigurationBasedServerList
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ServerListFilter ribbonServerListFilter: ZonePreferenceServerListFilter
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ILoadBalancer ribbonLoadBalancer: ZoneAwareLoadBalancer
二、準備工作
這一篇文章基於上一篇文章的工程,啓動eureka-server 工程;啓動service-hi工程,它的端口爲8762;將service-hi的配置文件的端口改爲8763,並啓動,這時你會發現:service-hi在eureka-server註冊了2個實例,這就相當於一個小的集羣。訪問localhost:8761如圖所示:
如何一個工程啓動多個實例,請看這篇文章:https://blog.csdn.net/forezp/article/details/76408139
重新新建一個spring-boot工程,取名爲:service-ribbon;
在它的pom.xml文件分別引入起步依賴spring-cloud-starter-eureka、spring-cloud-starter-ribbon、spring-boot-starter-web,代碼如下:
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.forezp</groupId> <artifactId>service-ribbon</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>service-ribbon</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.2.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka</artifactId> </dependency> <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-test</artifactId> <scope>test</scope> </dependency> </dependencies> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>Dalston.RC1</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-milestones</id> <name>Spring Milestones</name> <url>https://repo.spring.io/milestone</url> <snapshots> <enabled>false</enabled> </snapshots> </repository> </repositories> </project> 在工程的配置文件指定服務的註冊中心地址爲http://localhost:8761/eureka/,程序名稱爲 service-ribbon,程序端口爲8764。配置文件application.yml如下:
eureka: client: serviceUrl: defaultZone: http://localhost:8761/eureka/ server: port: 8764 spring: application: name: service-ribbon
在工程的啓動類中,通過@EnableDiscoveryClient向服務中心註冊;並且向程序的ioc注入一個bean: restTemplate;並通過@LoadBalanced註解表明這個restRemplate開啓負載均衡的功能。
@SpringBootApplication @EnableDiscoveryClient public class ServiceRibbonApplication { public static void main(String[] args) { SpringApplication.run(ServiceRibbonApplication.class, args); } @Bean @LoadBalanced RestTemplate restTemplate() { return new RestTemplate(); } }
寫一個測試類HelloService,通過之前注入ioc容器的restTemplate來消費service-hi服務的“/hi”接口,在這裏我們直接用的程序名替代了具體的url地址,在ribbon中它會根據服務名來選擇具體的服務實例,根據服務實例在請求的時候會用具體的url替換掉服務名,代碼如下:
@Service public class HelloService { @Autowired RestTemplate restTemplate; public String hiService(String name) { return restTemplate.getForObject("http://SERVICE-HI/hi?name="+name,String.class); } }
寫一個controller,在controller中用調用HelloService 的方法,代碼如下:
/** * Created by fangzhipeng on 2017/4/6. */ @RestController public class HelloControler { @Autowired HelloService helloService; @RequestMapping(value = "/hi") public String hi(@RequestParam String name){ return helloService.hiService(name); } }
在瀏覽器上多次訪問http://localhost:8764/hi?name=forezp,瀏覽器交替顯示:
hi forezp,i am from port:8762
hi forezp,i am from port:8763
這說明當我們通過調用restTemplate.getForObject(“http://SERVICE-HI/hi?name=”+name,String.class)方法時,已經做了負載均衡,訪問了不同的端口的服務實例。
四、此時的架構
- 一個服務註冊中心,eureka server,端口爲8761
- service-hi工程跑了兩個實例,端口分別爲8762,8763,分別向服務註冊中心註冊
- sercvice-ribbon端口爲8764,向服務註冊中心註冊
- 當sercvice-ribbon通過restTemplate調用service-hi的hi接口時,因爲用ribbon進行了負載均衡,會輪流的調用service-hi:8762和8763 兩個端口的hi接口;
源碼下載:https://github.com/forezp/SpringCloudLearning/tree/master/chapter2