Spring Cloud Netflix - Hystrix

Spring Cloud Netflix - Hystrix

什么是Hystrix

Hystrix是Netflix开源的一款针对分布式系统的延迟和容错库，目的是用来隔离分布式服务故障。它提供线程和信号量隔离，以减少不同服务之间资源竞争带来的相互影响;提供优雅降级机制;提供熔断机制使得服务可以快速失败，而不是一直阻塞等待服务响应，并能从中快速恢复。Hystrix通过这些机制来阻止级联失败并保证系统弹性、可用。

服务熔断

服务提供者(Hystrix)

springcloud-provider-dept-hystrix-8001

依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    <version>2.2.2.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    <version>2.2.2.RELEASE</version>
</dependency>
<!--完善监控信息-->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

配置

server:
  port: 8001
mybatis:
  type-aliases-package: cn.pinked.springcloud.pojo
  mapper-locations: classpath:mybatis/mapper/*.xml
  configuration:
    cache-enabled: true
spring:
  application:
    name: springcloud-provider-dept
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/db01?userUnicode=true&characterEncoding=utf-8&useSSL=true
    username: root
    password: 123456

eureka:
  client:
    service-url:
      defaultZone: http://localhost:7001/eureka/ #注册中心地址
  instance:
    instance-id: provider-dept-hystrix-8001 #Status中的id

#路径/actuator/info页面下的json信息
info:
  app: provider1(hystrix)
  admin: pinked

#以上与springcloud-provider-dept-8001相同
#以下为hystrix监控配置

management:
  endpoints:
    web:
      exposure:
        include: hystrix.stream

控制器controller

@GetMapping("/dept/{id}")
@HystrixCommand(fallbackMethod = "hystrixGet")//当方法失败时, 回调hystrixGet方法
public Dept get(@PathVariable("id") Long id) {
    Dept dept = deptService.queryById(id);
    if (dept == null) {
        throw new RuntimeException("不存在id=>" + id + "的用户");
    }
    return dept;
}

public Dept hystrixGet(@PathVariable("id") Long id) {
    return new Dept().setDnum(id).setDname("id=>" + id + "用户不存在").setDb_source("notFound");
}

启动器

@SpringBootApplication
@EnableEurekaClient //注册到Eureka
@EnableDiscoveryClient //服务发现
@EnableCircuitBreaker //添加熔断机制支持
public class DeptProviderHystrix_8001 {
    public static void main(String[] args) {
        SpringApplication.run(DeptProviderHystrix_8001.class, args);
    }
}

总结

服务提供者在服务异常的情况下，可以将服务请求转发至相应的服务异常处理方法中，以确保整个服务过程不会被阻塞。启动备用的方法，避免报500异常。

服务降级

公共api

springcloud-api

@Component
public class DeptClientServiceFallbackFactory implements FallbackFactory {
    public DeptClientService create(Throwable throwable) {
        return new DeptClientService() {
            public List<Dept> queryAll() {
                return null;
            }

            public Dept queryById(Long id) {
                return new Dept().setDnum(id).setDname("未找到id=>" + id + ", 服务已关闭").setDb_source("notFount");
            }

            public boolean addDept(Dept dept) {
                return false;
            }
        };
    }
}

手写一个类继承FallbackFactory，从写里面的方法，假设当服务器关闭之后，用户来访问不会报异常而是告诉用户不能用。

@Service
@FeignClient(value = "SPRINGCLOUD-PROVIDER-DEPT", fallbackFactory = DeptClientServiceFallbackFactory.class)
public interface DeptClientService {

    @GetMapping("/dept")
    List<Dept> queryAll();

    @GetMapping("/dept/{id}")
    Dept queryById(@PathVariable("id") Long id);

    @PostMapping("/dept")
    boolean addDept(Dept dept);
}

服务消费者(Feign)

springcloud-consumer-dept-feign

配置

feign:
  hystrix:
    enabled: true

Dashboard监控

springcloud-consumer-hystrix-dashboard

依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    <version>2.2.2.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
    <version>2.2.2.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
    <version>2.2.2.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    <version>2.2.2.RELEASE</version>
</dependency>

被监控的提供者需要有actuator和hystrix依赖

配置

server:
  port: 9001
eureka:
  client:
    register-with-eureka: false
    fetch-registry: false

启动器

@SpringBootApplication
@EnableHystrixDashboard //开启监控
public class DeptConsumerDashboard_9001 {
    public static void main(String[] args) {
        SpringApplication.run(DeptConsumerDashboard_9001.class, args);
    }
}

测试