服务熔断 1、环境搭建1、启动Nacos、Sentinel2、新建9003、9004两个模块pom<!-- API --> <dependency> <groupId>com.sw</groupId> <artifactId>cloud-api-commons</artifactId> <version>1.0-SNAPSHOT</version> </dependency> <!-- Nacos --> <dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-nacos-discovery</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-actuator</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <scope>runtime</scope> <optional>true</optional> </dependency>ymlserver: port: 9003 spring: application: name: nacos-payment-provider cloud: nacos: discovery: server-addr: localhost:8848 management: endpoints: web: exposure: include: '*'启动类@SpringBootApplication @EnableDiscoveryClient public class PaymentMain9003 { public static void main(String[] args) { SpringApplication.run(PaymentMain9003.class, args); } }controller(此处的虚拟数据库是为了方便演示)@RestController @RequestMapping("/payment") public class PaymentController { @Value("${server.port}") private String serverPort; public static Map<Long, Payment> map = new HashMap<>(); static { map.put(1L, new Payment(1L, "螺蛳粉01")); map.put(2L, new Payment(2L, "螺蛳粉02")); map.put(3L, new Payment(3L, "螺蛳粉03")); } @GetMapping("/{id}") public CommonResult<Payment> payment(@PathVariable("id")Long id){ Payment payment = map.get(id); CommonResult<Payment> result = new CommonResult<>(200, "serverPort: " + serverPort, payment); return result; } }注：9004构建步骤与9003一致2、新建8884模块pom同理9004、9004模块ymlserver: port: 8884 spring: application: name: nacos-order-consumer cloud: nacos: discovery: server-addr: localhost:8848 sentinel: transport: # sentinel dashboard地址 dashboard: localhost:8080 # 默认8719端口，如果8719被占用，默认递增 port: 8719 service-url: nacos-user-service: http://nacos-payment-provider management: endpoints: web: exposure: include: '*'启动类@SpringBootApplication @EnableDiscoveryClient public class OrderMain84 { public static void main(String[] args) { SpringApplication.run(OrderMain84.class, args); } }config配置类@Configuration public class ApplicationContextConfig { @Bean @LoadBalanced public RestTemplate getRestTemplate(){ return new RestTemplate(); } }controller@RestController @RequestMapping("/consumer") public class CircleBreakerController { public static final String SERVICE_URL = "http://nacos-payment-provider"; @Autowired private RestTemplate restTemplate; @GetMapping(value = "fallback/{id}", produces = {"application/json;charset=UTF-8"}) @SentinelResource("fallback") public CommonResult<Payment> fallback(@PathVariable("id")Long id){ CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/payment/" + id, CommonResult.class, id); if (id ==4){ throw new IllegalArgumentException("参数异常！"); }else if (result.getData() == null){ throw new NullPointerException("没有找到对应id的记录！"); } return result; } }指定降级方法@RestController @RequestMapping("/consumer") public class CircleBreakerController { public static final String SERVICE_URL = "http://nacos-payment-provider"; @Autowired private RestTemplate restTemplate; @GetMapping(value = "fallback/{id}", produces = {"application/json;charset=UTF-8"}) //@SentinelResource("fallback") @SentinelResource(value = "fallback", fallback = "handlerFallback") //fallback只负责业务异常 public CommonResult<Payment> fallback(@PathVariable("id")Long id){ CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/payment/" + id, CommonResult.class, id); if (id ==4){ throw new IllegalArgumentException("参数异常！"); }else if (result.getData() == null){ throw new NullPointerException("没有找到对应id的记录！"); } return result; } public CommonResult handlerFallback(@PathVariable("id")Long id, Throwable e){ Payment payment = new Payment(id, "null"); return new CommonResult(444,"handlerFallback,异常内容：" + e.getMessage(), payment); } }2、测试启动测试：注：此处没有使用Sentinel来配置降级规则，但却降级成功，是因为fallback用于管理异常，当业务发生异常时，可以降级到指定的方法为业务添加blockhandler@RestController @RequestMapping("/consumer") public class CircleBreakerController { public static final String SERVICE_URL = "http://nacos-payment-provider"; @Autowired private RestTemplate restTemplate; @GetMapping(value = "fallback/{id}", produces = {"application/json;charset=UTF-8"}) //@SentinelResource("fallback") //@SentinelResource(value = "fallback", fallback = "handlerFallback") //fallback只负责业务异常 @SentinelResource(value = "fallback", blockHandler = "blockHandler") //blockHandler只负责sentinel控制台的配置 public CommonResult<Payment> fallback(@PathVariable("id")Long id){ CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/payment/" + id, CommonResult.class, id); if (id ==4){ throw new IllegalArgumentException("参数异常！"); }else if (result.getData() == null){ throw new NullPointerException("没有找到对应id的记录！"); } return result; } // public CommonResult handlerFallback(@PathVariable("id")Long id, Throwable e){ // Payment payment = new Payment(id, "null"); // return new CommonResult(444,"handlerFallback,异常内容：" + e.getMessage(), payment); // } public CommonResult blockHandler(@PathVariable("id")Long id, BlockException exception){ Payment payment = new Payment(id, "null"); return new CommonResult(444,"blockHandler,异常内容：" + exception.getMessage(), payment); } }测试结果:注：可以看到返回结果直接报错，并没有降级，所以说blockHandler只适用于Sentinel配置的规则同时配置fallback和blockHandler@RestController @RequestMapping("/consumer") public class CircleBreakerController { public static final String SERVICE_URL = "http://nacos-payment-provider"; @Autowired private RestTemplate restTemplate; @GetMapping(value = "fallback/{id}", produces = {"application/json;charset=UTF-8"}) //@SentinelResource("fallback") //@SentinelResource(value = "fallback", fallback = "handlerFallback") //fallback只负责业务异常 //@SentinelResource(value = "fallback", blockHandler = "blockHandler") //blockHandler只负责sentinel控制台的配置 @SentinelResource(value = "fallback", fallback = "handlerFallback", blockHandler = "blockHandler") public CommonResult<Payment> fallback(@PathVariable("id")Long id){ CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/payment/" + id, CommonResult.class, id); if (id ==4){ throw new IllegalArgumentException("参数异常！"); }else if (result.getData() == null){ throw new NullPointerException("没有找到对应id的记录！"); } return result; } public CommonResult handlerFallback(@PathVariable("id")Long id, Throwable e){ Payment payment = new Payment(id, "null"); return new CommonResult(444,"handlerFallback,异常内容：" + e.getMessage(), payment); } public CommonResult blockHandler(@PathVariable("id")Long id, BlockException exception){ Payment payment = new Payment(id, "null"); return new CommonResult(444,"blockHandler,异常内容：" + exception.getMessage(), payment); } } 配置Sentinel规则：结果：可以看到，同时配置fallback和blockHandler，blockHandler的优先级更高exceptionsToIgnore属性@RestController @RequestMapping("/consumer") public class CircleBreakerController { public static final String SERVICE_URL = "http://nacos-payment-provider"; @Autowired private RestTemplate restTemplate; @GetMapping(value = "fallback/{id}", produces = {"application/json;charset=UTF-8"}) //@SentinelResource("fallback") //@SentinelResource(value = "fallback", fallback = "handlerFallback") //fallback只负责业务异常 //@SentinelResource(value = "fallback", blockHandler = "blockHandler") //blockHandler只负责sentinel控制台的配置 @SentinelResource(value = "fallback", fallback = "handlerFallback", blockHandler = "blockHandler", exceptionsToIgnore = {IllegalArgumentException.class}) public CommonResult<Payment> fallback(@PathVariable("id")Long id){ CommonResult<Payment> result = restTemplate.getForObject(SERVICE_URL + "/payment/" + id, CommonResult.class, id); if (id ==4){ throw new IllegalArgumentException("参数异常！"); }else if (result.getData() == null){ throw new NullPointerException("没有找到对应id的记录！"); } return result; } public CommonResult handlerFallback(@PathVariable("id")Long id, Throwable e){ Payment payment = new Payment(id, "null"); return new CommonResult(444,"handlerFallback,异常内容：" + e.getMessage(), payment); } public CommonResult blockHandler(@PathVariable("id")Long id, BlockException exception){ Payment payment = new Payment(id, "null"); return new CommonResult(444,"blockHandler,异常内容：" + exception.getMessage(), payment); } }测试结果：注：使用exceptionsToIgnore指定异常类，表示当前方法如果抛出了指定的异常，不进行降级处理，直接返回抛出的异常结果图片来源：尚硅谷 - 周阳 - Spring Cloud Alibaba

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：