5、spring cloud:Hystrix

Hystrix原理：

Hystrix原理.png

深入理解Hystrix之文档翻译 - CSDN博客

Hystrix使用：

使用方式一：自定义Hystrix请求命令的方式

Spring Cloud中Hystrix的请求缓存 - 个人文章 - SegmentFault 思否
hystrix缓存功能的使用 - CSDN博客
通过方法重载开启缓存

com.netflix.hystrix.contrib.javanica.aop.aspectj.HystrixCommandAspect
com.netflix.hystrix.HystrixCommand

public class BookCommand extends HystrixCommand<Book> {
    private RestTemplate restTemplate;
    private Long id;

    @Override
    protected Book getFallback() {
        Throwable executionException = getExecutionException();
        System.out.println(executionException.getMessage());
        return new Book("宋诗选注", 88, "钱钟书", "三联书店");
    }

    @Override
    protected Book run() throws Exception {
        return restTemplate.getForObject("http://HELLO-SERVICE/getbook5/{1}", Book.class,id);
    }

    public BookCommand(Setter setter, RestTemplate restTemplate,Long id) {
        super(setter);
        this.restTemplate = restTemplate;
        this.id = id;
    }

    @Override
    protected String getCacheKey() {
        return String.valueOf(id);
    }
}

   BookCommand bc1 = new BookCommand(HystrixCommand.Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("")).andCommandKey(commandKey), restTemplate, 1l);
    Book e1 = bc1.execute();

@RequestMapping("/test5")
public Book test5() {
    HystrixCommandKey commandKey = HystrixCommandKey.Factory.asKey("commandKey");
    HystrixRequestContext.initializeContext();
    BookCommand bc1 = new BookCommand(HystrixCommand.Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("")).andCommandKey(commandKey), restTemplate, 1l);
    Book e1 = bc1.execute();
    BookCommand bc2 = new BookCommand(HystrixCommand.Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("")).andCommandKey(commandKey), restTemplate, 1l);
    Book e2 = bc2.execute();
    BookCommand bc3 = new BookCommand(HystrixCommand.Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("")).andCommandKey(commandKey), restTemplate, 1l);
    Book e3 = bc3.execute();
    System.out.println("e1:" + e1);
    System.out.println("e2:" + e2);
    System.out.println("e3:" + e3);
    return e1;
}

Spring boot使用

@EnableCircuitBreaker
@EnableDiscoveryClient
@SpringBootApplication
public class ConsumerApplication {

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

@Service
public class UserService {
    @Autowired
    RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "userFallback", commandKey = "userKey")
    public User user(String name) {
        User user = restTemplate.getForEntity("http://HELLO-SERVICE/hello1?name={1}", User.class, name).getBody();
        return user;
    }

    public String userFallback() {
        return "error";
    }
}

参考

Hystrix基于RxJava的异步执行模式 - CSDN博客

How it Works · Netflix/Hystrix Wiki · GitHub
Hystrix浅入浅出：（二）断路器和滑动窗口 - CSDN博客