摘要：實(shí)戰(zhàn)五概要什么是怎么用常見(jiàn)配置介紹什么是是分布式系統(tǒng)處理超時(shí)和錯(cuò)誤的機(jī)制如下圖所示分布式系統(tǒng)中某個(gè)用戶請(qǐng)求依賴(lài)服務(wù)當(dāng)此請(qǐng)求并發(fā)超過(guò)的時(shí)候服務(wù)處理速度變慢但是服務(wù)還是被調(diào)用大量請(qǐng)求會(huì)阻塞在服務(wù)器上影響其它整個(gè)服務(wù)在復(fù)雜的分布式架構(gòu)的應(yīng)用程序

什么是Spring Cloud Netflix Hystrix?

怎么用 Spring Cloud Netflix Hystrix?

Hystrix常見(jiàn)配置介紹

Spring Cloud Netflix Hystrix是分布式系統(tǒng)處理超時(shí)和錯(cuò)誤的機(jī)制,如下圖所示,分布式系統(tǒng)中某個(gè)用戶請(qǐng)求依賴(lài)A,H,I,P服務(wù).

當(dāng)此請(qǐng)求并發(fā)超過(guò)50的時(shí)候,服務(wù)I處理速度變慢,但是服務(wù)I還是被調(diào)用.


大量請(qǐng)求會(huì)阻塞在Tomcat服務(wù)器上,影響其它整個(gè)服務(wù).在復(fù)雜的分布式架構(gòu)的應(yīng)用程序有很多的依賴(lài),都會(huì)不可避免地在某些時(shí)候失敗.高并發(fā)的依賴(lài)失敗時(shí)如果沒(méi)有隔離措施,當(dāng)前應(yīng)用服務(wù)就有被拖垮的風(fēng)險(xiǎn).
Spring Cloud Netflix Hystrix就是隔離措施的一種實(shí)現(xiàn),可以設(shè)置在某種超時(shí)或者失敗情形下斷開(kāi)依賴(lài)調(diào)用或者返回指定邏輯,從而提高分布式系統(tǒng)的穩(wěn)定性.

百說(shuō)不如一run,構(gòu)造一個(gè)例子來(lái)實(shí)現(xiàn),例子要實(shí)現(xiàn)使用Hystrix的Fallback(失敗后)邏輯來(lái)處理錯(cuò)誤情景
1.Eureka Server,和Eureka Client跟之前一樣,只需改造Eureka Sentence
2.Eureka Sentence 添加pom依賴(lài)

        
            org.springframework.cloud
            spring-cloud-starter-hystrix
        
        
            org.springframework.cloud
            spring-cloud-starter-hystrix-dashboard
        

3.Eureka Sentence的Application添加hystrix注解

@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
@EnableHystrix
@EnableHystrixDashboard
public class ApplicationSentence {
    public static void main(String[] args) {
        SpringApplication.run(ApplicationSentence.class, args);
    }
}

4.Eureka Sentence WordServiceImpl在subject,adjective,noun上添加HystrixCommand注解并實(shí)現(xiàn)相應(yīng)的fallback邏輯.

@Service
public class WordServiceImpl implements WordService {

    @Autowired
    VerbClient verbClient;
    @Autowired
    SubjectClient subjectClient;
    @Autowired
    ArticleClient articleClient;
    @Autowired
    AdjectiveClient adjectiveClient;
    @Autowired
    NounClient nounClient;
   

    @Override
    @HystrixCommand(fallbackMethod="getFallbackSubject")
    public String getSubject() {
        return subjectClient.getWord();
    }



    @Override
    public String getVerb() {
        return verbClient.getWord();
    }

    @Override
    public String getArticle() {
        return articleClient.getWord();
    }

    @Override
    @HystrixCommand(fallbackMethod="getFallbackAdjective")
    public String getAdjective() {
        return adjectiveClient.getWord();
    }

 
    @HystrixCommand(fallbackMethod="getFallbackNoun")
    public String getNoun() {
        return nounClient.getWord();
    }

    public String getFallbackSubject() {
        return "某人";
    }

    public String getFallbackAdjective() {
        return "";
    }

    public String getFallbackNoun() {
        return "某物";
    }
}

5.依次啟動(dòng)Eureka Server,Eureka Client,Eureka Sentence,這個(gè)跟之前一樣造句,停掉subject,noun服務(wù),可以看到其可以走fallback邏輯.
6.使用異步和reactive形式的Hystrix,修改getSubject()為Future,修改getNoun()為Observable.SentenceServiceImpl也做相應(yīng)的修改.

@Service
public class WordServiceImpl implements WordService {

    @Autowired
    VerbClient verbClient;
    @Autowired
    SubjectClient subjectClient;
    @Autowired
    ArticleClient articleClient;
    @Autowired
    AdjectiveClient adjectiveClient;
    @Autowired
    NounClient nounClient;
    @Override
    @HystrixCommand(fallbackMethod = "getFallbackSubject")
    public Future getSubject() {
        return new AsyncResult() {
            @Override
            public String invoke() {
                return subjectClient.getWord();
            }
        };
    }

//    @Override
//    @HystrixCommand(fallbackMethod="getFallbackSubject")
//    public String getSubject() {
//        return subjectClient.getWord();
//    }



    @Override
    public String getVerb() {
        return verbClient.getWord();
    }

    @Override
    public String getArticle() {
        return articleClient.getWord();
    }

    @Override
    @HystrixCommand(fallbackMethod="getFallbackAdjective")
    public String getAdjective() {
        return adjectiveClient.getWord();
    }

    @Override
    @HystrixCommand(fallbackMethod="getFallbackNoun")
    public Observable getNoun() {
        return Observable.create(new Observable.OnSubscribe() {
            @Override
            public void call(Subscriber observer) {
                try {
                    if (!observer.isUnsubscribed()) {
                        observer.onNext(nounClient.getWord());
                        observer.onCompleted();
                    }
                } catch (Exception e) {
                    observer.onError(e);
                }
            }
        });
    }
//    @HystrixCommand(fallbackMethod="getFallbackNoun")
//    public String getNoun() {
//        return nounClient.getWord();
//    }

    public String getFallbackSubject() {
        return "某人";
    }

    public String getFallbackAdjective() {
        return "";
    }

    public String getFallbackNoun() {
        return "某物";
    }
}

SentenceServiceImpl修改成下面

@Service
public class SentenceServiceImpl implements SentenceService {

    @Autowired WordService wordService;


    /**
     * Assemble a sentence by gathering random words of each part of speech:
     */
    public String buildSentence() {

        final List nounList = Lists.newArrayList();
        wordService.getNoun().subscribe(new Subscriber() {
            @Override
            public void onCompleted() {

            }

            @Override
            public void onError(Throwable e) {

            }

            @Override
            public void onNext(String s) {
                nounList.add(s);
            }
        });

        try {
            return String.format("%s %s %s %s %s.", wordService.getSubject().get(), wordService.getVerb(),
                    wordService.getArticle(), wordService.getAdjective(), nounList.get(0));
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        return "error";
    }

}

7.查看Hystrix dashboard可以看到方法調(diào)用的統(tǒng)計(jì)信息
訪問(wèn)http://127.0.0.1:8020/hystrix并輸入http://127.0.0.1:8020/hystrix...可以查看Hystrix接口調(diào)用信息