11、RestTemplate+Ribbon整合断路器Hystrix
在微服务架构中,根据业务需求拆分成一个个的微小服务,然后服务与服务之间可以相互RPC远程调用。在Spring Cloud可以使用RestTemplate+Ribbon或者Feign来进行RPC远程调用。为了保证服务高可用性,单个服务通常会进行集群部署。由于网络原因或者自身的原因,服务并不能保证百分之一百可用,如果服务方出现问题,调用这个服务就会出现线程阻塞,此时若有出现大量请求,导致服务方瘫痪。这时断路器就派上用场了。
当对某个服务的调用的不可用达到一个阀值(Hystric 默认是5秒20次) 断路器将会被自动被打开。断路打开后, fallback方法可以直接返回一个预先设置的固定值。
1、 新建项目sc-eureka-client-consumer-ribbon-hystrix,对应的pom.xml文件
<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>spring-cloud</groupId>
<artifactId>sc-eureka-client-consumer-ribbon</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>sc-eureka-client-consumer-ribbon</name>
<url>http://maven.apache.org</url>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.4.RELEASE</version>
</parent>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Finchley.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<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.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<!-- <dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-ribbon</artifactId>
<version>1.4.5.RELEASE</version>
</dependency> -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
<version>1.4.5.RELEASE</version>
</dependency> -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
<version>2.0.1.RELEASE</version>
</dependency>
</dependencies>
</project>
备注:spring-cloud-starter-hystrix已经在spring cloud 2.x标注成过期。推荐使用spring-cloud-starter-netflix-hystrix
2、 新建spring boot 启动类ConsumerApplication.java
package sc.consumer;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
@SpringBootApplication
@EnableEurekaClient
@EnableHystrix
public class ConsumerHystrixApplication {
public static void main(String[] args) {
SpringApplication.run(ConsumerHystrixApplication.class, args);
}
}
可以看出这个启动类只是《服务发现&服务消费者Ribbon》的启动类添加多了一个注解EnableHystrix(启动断路器)
3、 编写服务类,并添加断路器注解
package sc.consumer.service.impl;
import java.util.HashMap;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
import com.github.andrewoma.dexx.collection.ArrayList;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import sc.consumer.model.User;
import sc.consumer.service.UserService;
@Service
public class UserServiceImpl implements UserService{
@Autowired
private RestTemplate restTemplate;
@HystrixCommand(fallbackMethod = "getUserError")
@Override
public Map<String, Object> getUser(Long id) {
return restTemplate.getForObject("http://sc-eureka-client-provider:8200/user/getUser/{1}", Map.class, id);
}
public Map<String, Object> getUserError(Long id){
Map<String, Object> map = new HashMap<String, Object>();
map.put("code", "000000");
map.put("msg", "ok");
User u = new User();
u.setId(-1L);
u.setUserName("failName");
map.put("body", u);
return map;
}
@HystrixCommand(fallbackMethod = "listUserError")
@Override
public Map<String, Object> listUser() {
return restTemplate.getForObject("http://sc-eureka-client-provider:8200/user/listUser", Map.class);
}
public Map<String, Object> listUserError(){
Map<String, Object> map = new HashMap<String, Object>();
map.put("code", "000000");
map.put("msg", "ok");
map.put("body", new ArrayList<User>());
return map;
}
@HystrixCommand(fallbackMethod = "addUserError")
@Override
public Map<String, Object> addUser(User user) {
return restTemplate.postForObject("http://sc-eureka-client-provider:8200/user/addUser", user, Map.class);
}
public Map<String, Object> addUserError(User user){
Map<String, Object> map = new HashMap<String, Object>();
map.put("code", "000000");
map.put("msg", "ok");
map.put("body", 0);
return map;
}
@HystrixCommand(fallbackMethod = "updateUserError")
@Override
public Map<String, Object> updateUser(User user) {
restTemplate.put("http://sc-eureka-client-provider:8200/user/updateUser",user);
Map<String, Object> map = new HashMap<String, Object>();
map.put("code", "000000");
map.put("msg", "ok");
return map;
}
public Map<String, Object> updateUserError(User user){
Map<String, Object> map = new HashMap<String, Object>();
map.put("code", "000000");
map.put("msg", "ok");
map.put("body", 0);
return map;
}
@HystrixCommand(fallbackMethod = "deleteUserError")
@Override
public Map<String, Object> deleteUser(Long id) {
restTemplate.delete("http://sc-eureka-client-provider:8200/user/deleteUser/{id}", id);
Map<String, Object> map = new HashMap<String, Object>();
map.put("code", "000000");
map.put("msg", "ok");
return map;
}
public Map<String, Object> deleteUserError(Long id){
Map<String, Object> map = new HashMap<String, Object>();
map.put("code", "000000");
map.put("msg", "ok");
map.put("body", 0);
return map;
}
}
添加HystrixCommand注解,对应的参数fallbackMethod值为当方式服务方无法调用时,返回预设值得方法名。
4、 新建配置文件bootstrap.yml和application.yml
bootstrap.yml
server:
port: 5600
application.yml
spring:
application:
name: sc-eureka-client-consumer-ribbon-hystrix
eureka:
instance:
hostname: 127.0.0.1
client:
#由于该应用为注册中心,所以设置为false,代表不向注册中心注册自己
registerWithEureka: true
#由于注册中心的职责就是维护服务实例,它并不需要去检索服务,所以也设置为false
fetchRegistry: true
serviceUrl:
defaultZone: http://127.0.0.1:5001/eureka/
5、 其他项目文件参加下图
6、 分别启动注册中心sc-eureka-server和服务提供者sc-eureka-client-provider
7、 启动sc-eureka-client-consumer-ribbon-hystrix,并验证是否启动成功
方式一:查看日志
方式二:查看注册中心是否注册成功
8、 验证断路器是否起作用
(1) 服务提供者正常时访问:
http://127.0.0.1:5600/cli/user/getUser/4
正常返回数据库里的数据
(2) 服务提供者关闭时访问:
http://127.0.0.1:5600/cli/user/getUser/4
对比两个返回的数据,可以看出服务提供者关闭时,返回的数据是在程序写死的数据,如下图:
其他方法可以自行按照以上方式进行验证。