Spring Cloud 实战之服务提供与调用

eureka注册续约流程

1. 启动注册中心
2. 服务提供者生产服务并注册到服务中心中
3. 消费者从服务中心中获取服务并执行

服务提供

1.在spring-cloud-manage下创建一个子项目producer-service

pom.xml文件如下

<?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">
    <parent>
        <artifactId>spring-cloud-manage</artifactId>
        <groupId>org.springcloudmanage</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>producer-service</artifactId>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>

    <build>
        <finalName>producer-service</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2.创建启动类

Finchley版本已经不需要添加@EnableDiscoveryClient注解,Spring Cloud会自动识别。

@SpringBootApplication
public class ProducerServiceApplication {

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

}

3.配置文件

spring.application.name=producer-service
server.port=9001
#eureka
eureka.client.serviceUrl.defaultZone=http://localhost:8001/eureka/

• spring.application.name 服务提供者的名字
• server.por 服务端口号
• eureka.client.serviceUrl.defaultZone eureka的服务注册地址，如果eureka是多节点，多个地址逗号分隔，具体可以看上一篇博客:服务注册与发现。

多节点eureka服务注册如下：

eureka.client.serviceUrl.defaultZone=http://localhost:8001/eureka/,http://localhost:8002/eureka/

4.Action or Controller类

@RestController
@RequestMapping(value = "/test")
public class ProducerAction {

    @RequestMapping(value = "", method = RequestMethod.GET)
    public String test(String param) {
        return "param is " + param;
    }

}

5.启动服务

服务启动后，访问eureka主页http://localhost:8001/，即可看到如下页面，说明服务已经注册到eureka上了 

6.调用下试试

访问http://localhost:9001/test?param=test，看到返回结果如下

param is test

服务消费 ribbon

Ribbon 了，它是一个基于 HTTP 和 TCP 的客户端负载均衡器。它可以通过在客户端中配置ribbonServerList 来设置服务端列表去轮询访问以达到均衡负载的作用。

当 Ribbon 与 Eureka联合使用时，ribbonServerList会被DiscoveryEnabledNIWSServerList 重写，扩展成从 Eureka 注册中心中获取服务实例列表。同时它也会用 NIWSDiscoveryPing 来取代 IPing，它将职责委托给 Eureka 来确定服务端是否已经启动。

1.在spring-cloud-manage下创建一个子项目consumer-service

pom.xml文件如下

<?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">
    <parent>
        <artifactId>spring-cloud-manage</artifactId>
        <groupId>org.springcloudmanage</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>consumer-service</artifactId>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

spring-cloud-starter-netflix-eureka-client中已经引用了ribbon先关的jar，所需不需要再引入了

2.创建启动类

@SpringBootApplication
public class ConsumerServiceApplication {

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

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

}

3.配置文件

spring.application.name=consumer-service
server.port=9002
#eureka
eureka.client.serviceUrl.defaultZone=http://localhost:8001/eureka/

4.Action or Controller类

这里注入restTemplate，Spring Cloud Ribbon 自己有拦截器会对 服务名producer-service做解析，自动的去选取服务实例负载均衡调用，并将服务名替换成实际要请求的IP地址和端口

@RestController
@RequestMapping(value = "/ribbon/test")
public class ConsumerAction {

    @Autowired
    private RestTemplate restTemplate;

    @RequestMapping(value = "", method = RequestMethod.GET)
    public String test(String param) {
        String url = "http://producer-service/test/?param=" + param;
        return restTemplate.getForObject(url, String.class);
    }
    
}

5.启动服务

消费端服务启动成功后，可以看到erueka时已经显示注册成功了

5.调用消费端服务

访问http://localhost:9002/ribbon/test?param=ribbon-test ,可以看到如下结果，说明消费端服务接收到参数后，通过ribbon负载均衡，调用到producer-service的接口。

param is ribbon-test

控制台日志

2018-08-28 16:25:23.397  INFO 3791 --- [nio-9002-exec-1] c.netflix.config.ChainedDynamicProperty  : Flipping property: producer-service.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647
2018-08-28 16:25:23.414  INFO 3791 --- [nio-9002-exec-1] c.n.u.concurrent.ShutdownEnabledTimer    : Shutdown hook installed for: NFLoadBalancer-PingTimer-producer-service
2018-08-28 16:25:23.433  INFO 3791 --- [nio-9002-exec-1] c.netflix.loadbalancer.BaseLoadBalancer  : Client: producer-service instantiated a LoadBalancer: DynamicServerListLoadBalancer:{NFLoadBalancer:name=producer-service,current list of Servers=[],Load balancer stats=Zone stats: {},Server stats: []}ServerList:null
2018-08-28 16:25:23.440  INFO 3791 --- [nio-9002-exec-1] c.n.l.DynamicServerListLoadBalancer      : Using serverListUpdater PollingServerListUpdater
2018-08-28 16:25:23.462  INFO 3791 --- [nio-9002-exec-1] c.netflix.config.ChainedDynamicProperty  : Flipping property: producer-service.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647
2018-08-28 16:25:23.463  INFO 3791 --- [nio-9002-exec-1] c.n.l.DynamicServerListLoadBalancer      : DynamicServerListLoadBalancer for client producer-service initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=producer-service,current list of Servers=[192.168.101.238:9001],Load balancer stats=Zone stats: {defaultzone=[Zone:defaultzone;	Instance count:1;	Active connections count: 0;	Circuit breaker tripped count: 0;	Active connections per server: 0.0;]
},Server stats: [[Server:192.168.101.238:9001;	Zone:defaultZone;	Total Requests:0;	Successive connection failure:0;	Total blackout seconds:0;	Last connection made:Thu Jan 01 08:00:00 CST 1970;	First connection made: Thu Jan 01 08:00:00 CST 1970;	Active Connections:0;	total failure count in last (1000) msecs:0;	average resp time:0.0;	90 percentile resp time:0.0;	95 percentile resp time:0.0;	min resp time:0.0;	max resp time:0.0;	stddev resp time:0.0]
]}ServerList:org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList@12e48993
2018-08-28 16:25:24.447  INFO 3791 --- [erListUpdater-0] c.netflix.config.ChainedDynamicProperty  : Flipping property: producer-service.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647

可以启动多个producer-service服务测试下实际的负载均衡效果。

服务消费 feign

Feign是一个声明式的Web Service客户端，它使得编写Web Serivce客户端变得更加简单。我们只需要使用Feign来创建一个接口并用注解来配置它既可完成。它具备可插拔的注解支持，包括Feign注解和JAX-RS注解。Feign也支持可插拔的编码和解码。Spring Cloud为Feign增加了对Spring MVC注解的支持，还整合了Ribbon和Eureka来提供均衡负载的HTTP客户端实现。

在实际工作中，我们基本上都是使用Feign来完成调用的。我们通过一个例子来展现 Feign 如何方便的声明对 eureka-producer 服务的定义和调用。

1.consumer-service添加对feign的依赖

<?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">
    <parent>
        <artifactId>spring-cloud-manage</artifactId>
        <groupId>org.springcloudmanage</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>consumer-service</artifactId>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

2.启动类上加上feign所需注解

@EnableFeignClients
@SpringBootApplication
public class ConsumerServiceApplication {

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

}

3.配置文件

spring.application.name=consumer-service
server.port=9002
#eureka
eureka.client.serviceUrl.defaultZone=http://localhost:8001/eureka/
#开启Hystrix断路器
feign.hystrix.enabled=true
#断路器的超时时间需要大于ribbon的超时时间，不然不会触发重试,缺省为1000
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=5000

4.feign 调用

创建feign客户端调用类，其中name为所需调用的服务名，fallback使用Hystrix，当producer-service不可用时，对服务做降级，并返回友好提示

@FeignClient(name = "producer-service", fallback = ProducerServiceFeignClientHystrix.class)
public interface ProducerServiceFeignClient {

    @RequestMapping(value = "/test", method = RequestMethod.GET)
    String test(@RequestParam("param") String param);

}

==注意@RequestParam("param")中name必须要和producer-service服务中的参数名一致==

@Component
public class ProducerServiceFeignClientHystrix implements ProducerServiceFeignClient {
    @Override
    public String test(String param) {
        return "服务[producer-service]无法访问";
    }
}

访问http://localhost:9002/feign/test?param=feign-test，可以看到如下结果

param is feign-test

停止producer-service，再次访问http://localhost:9002/feign/test?param=feign-test，可以看到如下结果，说明fallback已经生效了

服务[producer-service]无法访问