微服务组件：服务容错hystrix

1. hystrix介绍

Hystrix是Netflix的一款开源组件，它通过熔断模式、隔离模式、回退（fallback）和限流等机制对服务进行弹性容错保护，保证系统的稳定性。

2. hystrix

3. hystrix使用

3-1 启动客户端

在spring boot启动Application类上，添加注解启动对hystrix的监控

@EnableCircuitBreaker

依赖调用逻辑

@Service
public class MengkaHystrixService {

    @HystrixCommand(fallbackMethod = "defaultFallbackMethod")
    public String alwaysFailsMethod() {
        throw new RuntimeException("Bad stuff has happened!");
    }

    @HystrixCommand(fallbackMethod = "failingFallbackMethod")
    public String alwaysFailsDownTheChainMethod() {
        throw new RuntimeException("Bad stuff continues to happen!");
    }

    @HystrixCommand(fallbackMethod = "defaultFallbackMethod")
    public String longRunningMethod() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return "this method takes too long!";
    }


    private String defaultFallbackMethod() {
        return "success";
    }

    @HystrixCommand(fallbackMethod = "secondFallbackMethod")
    private String failingFallbackMethod() {
        throw new RuntimeException("Bad stuff has happened!");
    }

    private String secondFallbackMethod() {
        return "more success";
    }
}

访问：

http://127.0.0.1:8073/hystrix.stream

已经可以获取hystrix依赖调用统计数据，说明启动成功。

3-2 启动hystrix-dashboard

maven依赖

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

启动hystrix-dashboard

@SpringBootApplication
@EnableHystrixDashboard
public class HystrixDashboardApplication {

    public static void main(String[] args) {
        new SpringApplicationBuilder(HystrixDashboardApplication.class).web(true).run(args);
    }
}

访问页面：

http://localhost:8030/hystrix.stream