spring cloud--服务容错保护Hystrix

简言之Hystrix的作用就是，在服务调用失败的时候，会返回一个错误的相应，而不是长时间的等待。

快速入门：
同样使用http://blog.csdn.net/wangpengzhi19891223/article/details/78840646中的例子对服务进行改造：

1，consumer中引入依赖：

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

1，ConsumerApplication.java 中使用注解开启断路器功能：

@EnableCircuitBreaker@EnableDiscoveryClient@SpringBootApplicationpublic class ConsumerApplication {    @Bean    @LoadBalanced    RestTemplate restTemplate(){        return new RestTemplate();    }    public static void main(String[] args){        SpringApplication.run(ConsumerApplication.class, args);    }}

新增HelloService类：

@Servicepublic class HelloService {    private final Logger logger = Logger.getLogger(HelloService.class);    @Autowired    RestTemplate restTemplate;    @HystrixCommand(fallbackMethod = "helloFallback")    public String helloService(){        long start = System.currentTimeMillis();        String result =  restTemplate.getForEntity("http://HELLO-SERVICE/hello",String.class).getBody();        logger.info("耗时：" + (System.currentTimeMillis() - start));        return  result;    }    public String helloFallback(){        return "error";    }}

改造ConsumerController，注入service实例：

@RestControllerpublic class ConsumerController {    @Autowired    RestTemplate restTemplate;    @Autowired    private HelloService helloService;    @RequestMapping(value = "/consumer", method = RequestMethod.GET)    public String helloConsumer(){     return  helloService.helloService();    }}

同样给出application.properties中的内容：

spring.application.name=ribbon-consumerserver.port=9000eureka.client.serviceUrl.defaultZone = http://peer1:1111/eureka/

启动项目，并关闭注册中心，访问：http://localhost:9000/consumer 返回：error,说明调用到了我们写断路器方法。

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改造一下service工程中的提供服务的hello方法：

@RestControllerpublic class HelloController {    private final Logger logger = Logger.getLogger(HelloController.class);    @Autowired    private DiscoveryClient client;    @RequestMapping(value = "/hello", method = RequestMethod.GET)    public String index() throws Exception{        ServiceInstance instance = client.getLocalServiceInstance();        int sleepTime = new Random().nextInt(3000);        logger.info("sleeptime"+sleepTime);        Thread.sleep(sleepTime);        logger.info("host:"+instance.getHost()+instance.getServiceId()+":"+instance.getPort());        return "New Hello world server!";    }}

当随机数休眠时间大于2000时，返回error
当小于2000的时候返回：New Hello world server!