SpringCloud微服务之hystrix(二)

偏执的太偏执、 2022-04-22 07:56 328阅读 0赞

## 前言 ##

上一小节为我们从概念上认识了Hystrix，本小节我们将通过实例来学习一下Hystrix的熔断机制以及Hystrux的断路器。

## 案例 ##

*  Eureka Server端编写(参考前例)  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70]
 *  Eureka Client端服务提供方编写。
    
     *  项目结构  
        ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 1]
     *  CoreCode
        
            @SpringBootApplication
            @EnableDiscoveryClient
            @EnableCircuitBreaker //开启Hystrix熔断机制
            public class MicroserviceDealBrokerHystrixApplication {
            
            	@Bean
            	@LoadBalanced
            	/**
            	 * 添加 @LoadBalanced 使该RestTemplate具备Ribbon均衡负载算法功能
            	 * @return
            	 */
            	public RestTemplate restTemplate() {
            		return new RestTemplate();
            	}
            
            	public static void main(String[] args) {
            		SpringApplication.run(MicroserviceDealBrokerHystrixApplication.class, args);
            	}
            }
        
            /**
             * SpringCould 2.0+需要为HystrixMricsStreamServlet手动注入到ServletRegistrationBean中
             * @author Administrator
             *
             */
            @Component
            public class HystrtixStreamServlet {
            	
            	@Bean
            	public ServletRegistrationBean<Servlet> getSerlvet(){
            		HystrixMetricsStreamServlet streamServlet = new HystrixMetricsStreamServlet();
            		ServletRegistrationBean<Servlet> registrationBean =  new ServletRegistrationBean<>(streamServlet);
            		registrationBean.setLoadOnStartup(1);
            		registrationBean.addUrlMappings("/hystrix.stream");
            		//registrationBean.addUrlMappings("/hystrix");
            		registrationBean.setName("HystrixMricsStreamServlet");
            		return registrationBean;
            	}
            }
        
            @RestController
            public class BrokerController {
            	@Autowired
            	private RestTemplate restTemplate;
            	
            	@Value("${server.port}")
            	private String port; // 注入普通字符串
            	
            	@GetMapping("/deal/{id}")
            	@HystrixCommand(fallbackMethod = "findByIdFallBack")
            	public Deal findById(@PathVariable Long id) {
            		return this.restTemplate.getForObject("http://microservice-deal-cloud/deal/" + id, Deal.class);
            	}
            	
            	/**
            	 * findById fallBack方法
            	 * 主方法与fallback方法应保持一致(入参、返回值)
            	 * @param id
            	 * @return
            	 */
            	public Deal findByIdFallBack(Long id){
            		Deal deal = new Deal();
            		deal.setId(id.intValue());
            		deal.setName("Dustyone");
            		deal.setPort(port);
            		return deal;
              }
            }
        
            server:
              port: 8082
            spring:
              application:
                name: microservice-deal-broker-cloud-hystrix
            eureka:
              client:
                serviceUrl:
                  defaultZone: http://localhost:8080/eureka/
              instance:
                prefer-ip-address: true
            
            #开放所有的监控节点
            management:
              endpoints:
                web:
                  exposure:
                    include: '*'
            
            #设置feign的hystrix响应超时时间(必须)
            hystrix:
              command:
                  default:
                    execution:
                      isolation:
                        thread:
                          timeoutInMilliseconds: 5000
        
            <?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>
            
            	<artifactId>microservice-deal-broker-cloud-hystrix</artifactId>
            	<packaging>jar</packaging>
            
            	<name>microservice-deal-broker-cloud-hystrix</name>
            	<description>Demo project for Spring Boot</description>
            
            	<parent>
            		<groupId>com.example</groupId>
            		<artifactId>microservice-deal-parent</artifactId>
            		<version>0.0.1-SNAPSHOT</version>
            	</parent>
            
            	<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-netflix-hystrix</artifactId>
            		</dependency>
            	</dependencies>
            
            </project>
 *  Eureka Client端服务提消费编写(单实例) (参考前例)。
 *  访问：[http://localhost:8082/deal/2][http_localhost_8082_deal_2]  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 2]  
    如上图所示，服务消费者和服务提供者正常时我们能通过消费者请求到提供者。
 *  现在我们把服务提供者手动shutdown掉，  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 3]
 *  然后再访问：[http://localhost:8082/deal/1][http_localhost_8082_deal_1]  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 4]
 *  然后我们访问：[http://localhost:8082/hystrix.stream][http_localhost_8082_hystrix.stream]  
    此时我们可以看到Hystrix 会一直再ping 降级服务(即服务提供者)，这就是所谓的断路器半开状态，一旦降级服务宕机，服务消费者就会一直去尝试访问降级服务。  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 5]
 *  然后我们重新将降级服务启动：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 6]
 *  访问：[http://localhost:8082/deal/2][http_localhost_8082_deal_2]  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 7]

此时所有服务又都正常了，能正常访问了，Hystrix 断路器关闭。

## 小结 ##

*  要使用Hystrix功能先加入Hystrix依赖：spring-cloud-starter-netflix-hystrix（V 2.0+）然后再主类上开起Hystrix熔断机制：@EnableCircuitBreaker
 *  对指定的方法添加FallBack方法：@HystrixCommand(fallbackMethod = “findByIdFallBack”)，需要注意的是：主方法与fallback方法应保持一致(入参、返回值)。
 *  对于SpringCloud V2.0+ 当我们使用Hystrix.stream来对查看断路器监控信息是需要自定义一个HystrixMetricsStreamServlet，并将该servlet加入到ServletRegistrationBean中。并尝试着开放所有的监控节点(建议)，当然如果你想对一些特定监控接口要求授权之后才能访问，可以自定义监控端点。
 *  本小节用的案例：microservice-deal-eureka、microservice-deal-cloud、microservice-deal-broker-cloud-hystrix

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70]: /images/20220422/a138b09afcbc4365b9cd8b48ad63aa9d.png
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[http_localhost_8082_deal_2]: http://localhost:8082/deal/2
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 2]: /images/20220422/8c851ceaa6ce4475801226ca0c311091.png
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[http_localhost_8082_deal_1]: http://localhost:8082/deal/1
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 4]: /images/20220422/0c2c3e10d65c4f9b945927b7b5eee3c3.png
[http_localhost_8082_hystrix.stream]: http://localhost:8082/hystrix.stream
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTI0Mzc3ODE_size_16_color_FFFFFF_t_70 5]: /images/20220422/076781d65c6644448b41dc983b8814df.png
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