Hystrix服务降级 Hystrix服务降级A、B、C三台服务器，A在某一时间段的负载很重，急需扩容，而此时间段B、C负载很小或没有访问量，需关闭其中的服务器，拿去给A扩容，以降低负载，同时设置fallback回调，让这个时间段需要访问B、C服务器的用户得到“服务暂时不可用或关闭”的信息，这个过程可以简单的比喻为服务降级。1、API接口设置fallback回调pojopackage com.sw.springcloud.pojo; import lombok.Data; import lombok.NoArgsConstructor; import lombok.experimental.Accessors; import java.io.Serializable; /** * @Author suaxi * @Date 2020/12/28 21:07 */ @Data @NoArgsConstructor @Accessors(chain = true) //链式编程 public class Dept implements Serializable { private Long deptno; private String dname; private String db_source; //数据存在哪个数据库 public Dept(String dname) { this.dname = dname; } } service接口package com.sw.springcloud.service; import com.sw.springcloud.pojo.Dept; import org.springframework.cloud.openfeign.FeignClient; import org.springframework.stereotype.Component; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.PostMapping; import java.util.List; /** * @Author suaxi * @Date 2020/12/29 20:02 */ @Component @FeignClient(value = "SPRINGCLOUD-PROVIDER-DEPT",fallbackFactory = DeptClientServiceFallbackFactory.class) public interface DeptClientService { @GetMapping("/dept/get/{id}") public Dept findById(@PathVariable("id")Long id); @GetMapping("/dept/list") public List<Dept> findAll(); @PostMapping("/dept/add") public boolean addDept(Dept dept); } FallbackFactoryService服务降级设置package com.sw.springcloud.service; import com.sw.springcloud.pojo.Dept; import feign.hystrix.FallbackFactory; import org.springframework.stereotype.Component; import java.util.List; /** * @Author suaxi * @Date 2020/12/30 9:33 * 服务降级 */ @Component public class DeptClientServiceFallbackFactory implements FallbackFactory { @Override public Object create(Throwable throwable) { return new DeptClientService() { @Override public Dept findById(Long id) { return new Dept() .setDeptno(id) .setDname("未查询到数据，该服务现已被关闭") .setDb_source("没有数据库信息"); } @Override public List<Dept> findAll() { return null; } @Override public boolean addDept(Dept dept) { return false; } }; } /* 服务熔断：服务端，某个服务超时或异常，引起熔断（类似于保险丝） 服务降级：客户端，从系统整体负载考虑，当某个服务熔断或关闭之后，服务将不再被调用 此时在客户端可以设置一个回调FallbackFactory，返回一个默认的缺省值，可以 提升用户体验，但服务质量随之下降 */ } 2、消费者端设置appliction.yml配置服务降级server: port: 80 eureka: client: register-with-eureka: false #不向注册中心注册自己（消费者端） service-url: defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/ #开启降级feign.hystrix feign: hystrix: enabled: true将RestTemplate注册到Spring容器中package com.sw.springcloud.config; import org.springframework.cloud.client.loadbalancer.LoadBalanced; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.client.RestTemplate; /** * @Author suaxi * @Date 2020/12/28 22:15 */ @Configuration public class ConfigBean { @Bean @LoadBalanced //注册Ribbon public RestTemplate getRestTemplate(){ return new RestTemplate(); } } SpringBoot启动类package com.sw.springcloud; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; import org.springframework.cloud.openfeign.EnableFeignClients; import org.springframework.context.annotation.ComponentScan; /** * @Author suaxi * @Date 2020/12/28 22:29 */ @SpringBootApplication @EnableEurekaClient @EnableFeignClients(basePackages = {"com.sw.springcloud"}) public class FeignDeptConsumer_80 { public static void main(String[] args) { SpringApplication.run(FeignDeptConsumer_80.class,args); } } 用户正常访问服务：微服务节点出现问题，服务降级：

Hystrix服务熔断 Hystrix服务熔断服务熔断：熔断机制是对应雪崩效应的一种微服务链路保护机制。当某个微服务不可用或响应时间太长，会进行服务的降级，进而熔断该节点微服务的调用，快速返回“错误的响应信息”，当该节点的调用恢复正常之后注册中心将其恢复至调用链路。Spring Cloud的熔断机制通过Hystrix实现，它会监控微服务间的调用状况，当失败的调用到一定阈值（缺省5秒内20次调用失败），就会启动熔断机制。具体实例：1、导入依赖<dependencies> <!--需要拿到实体类，配置api module--> <dependency> <groupId>com.sw</groupId> <artifactId>springcloud-api</artifactId> <version>1.0-SNAPSHOT</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-core</artifactId> </dependency> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-jetty</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka</artifactId> <version>1.4.7.RELEASE</version> </dependency> <!--actuator监控信息--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId> </dependency> <!--Hystrix--> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-hystrix</artifactId> <version>1.4.7.RELEASE</version> </dependency> </dependencies>2、daopackage com.sw.springcloud.dao; import com.sw.springcloud.pojo.Dept; import org.apache.ibatis.annotations.Mapper; import org.springframework.stereotype.Repository; import java.util.List; /** * @Author suaxi * @Date 2020/12/28 21:34 */ @Mapper @Repository public interface DeptDao { public boolean addDept(Dept dept); public Dept findDept(Long id); public List<Dept> findAll(); } 3、Service接口package com.sw.springcloud.service; import com.sw.springcloud.pojo.Dept; import java.util.List; /** * @Author suaxi * @Date 2020/12/28 21:34 */ public interface DeptService { public boolean addDept(Dept dept); public Dept findDept(Long id); public List<Dept> findAll(); } Service实现：package com.sw.springcloud.service; import com.sw.springcloud.dao.DeptDao; import com.sw.springcloud.pojo.Dept; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import java.util.List; /** * @Author suaxi * @Date 2020/12/28 21:42 */ @Service public class DeptServiceImpl implements DeptService{ @Autowired private DeptDao deptDao; @Override public boolean addDept(Dept dept) { return deptDao.addDept(dept); } @Override public Dept findDept(Long id) { return deptDao.findDept(id); } @Override public List<Dept> findAll() { return deptDao.findAll(); } } 4、controller注：hystrix熔断需开启注解@HystrixCommand(fallbackMethod = "hystrixGet")，且提供熔断后的备选方法package com.sw.springcloud.controller; import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand; import com.sw.springcloud.pojo.Dept; import com.sw.springcloud.service.DeptService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.cloud.client.ServiceInstance; import org.springframework.cloud.client.discovery.DiscoveryClient; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RestController; import java.util.List; /** * @Author suaxi * @Date 2020/12/28 21:44 * 提供RestFul服务 */ @RestController public class DeptController { @Autowired private DeptService deptService; @GetMapping("/dept/get/{id}") @HystrixCommand(fallbackMethod = "hystrixGet") public Dept get(@PathVariable("id")Long id){ Dept dept = deptService.findDept(id); if (dept==null){ throw new RuntimeException("不存在id为"+id+"的用户，或者信息无法找到"); } return dept; } //熔断后的备选方法 public Dept hystrixGet(@PathVariable("id")Long id){ Dept dept = deptService.findDept(id); return new Dept() .setDeptno(id) .setDname("不存在id为"+id+"的用户，或者信息无法找到,null-->@Hystrix") .setDb_source("No message in MySQL"); } } 5、SpringBoot启动类开启Hystrix注解支持package com.sw.springcloud; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; import org.springframework.cloud.netflix.eureka.EnableEurekaClient; /** * @Author suaxi * @Date 2020/12/28 21:49 */ @SpringBootApplication @EnableEurekaClient //服务启动后自动注册到Eureka中 @EnableDiscoveryClient //开启服务发现 @EnableCircuitBreaker //开启熔断器支持 public class DeptProviserHystrix_8088 { public static void main(String[] args) { SpringApplication.run(DeptProviserHystrix_8088.class,args); } } 6、appliction.yml配置（此处以单个节点配置为例，实际开发中的微服务节点不止一个）server: port: 8088 #mybatis配置 mybatis: type-aliases-package: com.sw.springcloud.pojo config-location: classpath:mybatis/mybatis-config.xml mapper-locations: classpath:mybatis/mapper/*.xml #Spring配置 spring: application: name: springcloud-provider-dept datasource: type: com.alibaba.druid.pool.DruidDataSource driver-class-name: com.mysql.cj.jdbc.Driver url: jdbc:mysql://localhost:3306/db01?useUnicode=true&character=UFT-8 username: root password: 123456 #配置Eureka，配置服务注册到哪里 eureka: client: service-url: defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/ instance: instance-id: springcloud-provider_dept-hystrix_8088 #修改Eureka默认描述信息 #info配置 info: app.name: springcloud-demo company.name: suaxi 当整个微服务调用出现问题时，前端反馈给用户的信息不是错误代码，而是熔断后的备选方法中定义的信息（即快速返回出现错误的响应信息）。用户正常查询信息：查询数据库中不存在的信息，即服务调用出现异常：