Spring Cloud學習（四）Hystrix

四、Hystrix進行容錯處理

1.Ribbon整合Hystrix

添加pom依賴：

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

在啓動類添加@EnableHystrix或@EnableCircuitBreaker註解，修改service層增加@HystrixCommand註解並標明fallbackMethod方法，添加遇到錯誤時返回的缺省方法，這個方法要和fallbackMethod中的方法名一致，參數要和原方法一致：

@Service
public class HelloServiceImpl implements HelloService {
    @Autowired
    RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "hiError",
            //配置具體見https://github.com/Netflix/Hystrix/wiki/Configuration
            commandProperties = {@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "5000"),//調用者等待命令執行的超時限制，超過此時間，HystrixCommand被標記爲TIMEOUT，並執行回退邏輯。
                    @HystrixProperty(name = "metrics.rollingStats.timeInMilliseconds", value = "10000"), //統計的滾動窗口的時間段大小。該屬性是線程池保持指標時間長短。
                    @HystrixProperty(name = "execution.isolation.strategy", value = "THREAD")},//Hystrix隔離策略有THREAD和SENSPHORE兩種，THREAD(線程隔離)HystrixCommand會在單獨線程執行 SENSPHORE(信號量隔離)在調用線程上執行，收到信號量限制
            threadPoolProperties = {@HystrixProperty(name = "coreSize", value = "1"),//線程池中核心線程數量
                    @HystrixProperty(name = "maxQueueSize",value = "10")})//隊列大小
    @Override
    public String getService() {
        return restTemplate.getForObject("http://service-offer/test,String.class);
    }

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

關掉所有服務提供者後在訪問服務消費者得到的結果是get error。

2.Feign整合Hystrix

Feign是動態代理接口，不能寫fallbackMethod，要新建一個類實現有@FeignClient的接口：

@Component
public class ServiceOfferFeignClientFallback implements ServiceOfferFeignClient {
    @Override
    public String getService() {
        return "get error from feign";
    }
}

在@FeignClient的接口上增加fallback屬性：

@FeignClient(name = "service-offer", fallback = ServicehiFeignClientFallback.class)

在application.yml中打開Hystrix的開關：

feign:
  hystrix:
    enabled: true

這樣Feign就整合了Hystrix。

Feign還可以通過FallbackFactory來整合，新建ServicOfferiFeignClientFallbackFactory類實現FallbackFactory<ServiceOfferFeignClient>接口：

@Component
public class ServiceOfferFeignClientFallbackFactory implements FallbackFactory<ServiceOfferFeignClient> {
    @Override
    public ServiceOfferFeignClient create(Throwable throwable) {
        return new ServiceOfferFeignClient() {
            @Override
            public String getService() {
                return "get from fallback factory";
            }
        };
    }
}

修改FeignClient接口：

@FeignClient(name = "service-hi", fallbackFactory = ServiceOfferFeignClientFallbackFactory.class)

這樣也可以實現斷路器。

如果某個服務要禁用Hystrix，添加如下配置類：

@Configuration
public class FeignDisableHystrixConfiguration {

    @Bean
    @Scope("prototype")
    public Feign.Builder feignBuilder(){
        return Feign.builder();
    }
}

然後在FeignClient的配置類中指定Feign.Builder的配置類即可：

@FeignClient(name = "service-offer", configuration = FeignDisableHystrixConfiguration.class)

3.Hystrix監控

添加Actuator依賴：

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

application.yml中增加actuator暴露的節點hystrix.stream：

management:
  endpoints:
    web:
      exposure:
        include: health,info,env,hystrix.stream

重新啓動服務先訪問一次服務消費者的服務，然後訪問localhost:8765/actuator/hystrix.stream,可以看到頁面反覆出先如下內容：

ping: 

data: {"type":"HystrixCommand","name":"ServicehiFeignClient#hiService(String)","group":"service-hi","currentTime":1551319254509,"isCircuitBreakerOpen":false,"errorPercentage":0,"errorCount":0,"requestCount":0,"rollingCountBadRequests":0,"rollingCountCollapsedRequests":0,"rollingCountEmit":0,"rollingCountExceptionsThrown":0,"rollingCountFailure":0,"rollingCountFallbackEmit":0,"rollingCountFallbackFailure":0,"rollingCountFallbackMissing":0,"rollingCountFallbackRejection":0,"rollingCountFallbackSuccess":0,"rollingCountResponsesFromCache":0,"rollingCountSemaphoreRejected":0,"rollingCountShortCircuited":0,"rollingCountSuccess":0,"rollingCountThreadPoolRejected":0,"rollingCountTimeout":0,"currentConcurrentExecutionCount":0,"rollingMaxConcurrentExecutionCount":0,"latencyExecute_mean":470,"latencyExecute":{"0":470,"25":470,"50":470,"75":470,"90":470,"95":470,"99":470,"99.5":470,"100":470},"latencyTotal_mean":474,"latencyTotal":{"0":474,"25":474,"50":474,"75":474,"90":474,"95":474,"99":474,"99.5":474,"100":474},"propertyValue_circuitBreakerRequestVolumeThreshold":20,"propertyValue_circuitBreakerSleepWindowInMilliseconds":5000,"propertyValue_circuitBreakerErrorThresholdPercentage":50,"propertyValue_circuitBreakerForceOpen":false,"propertyValue_circuitBreakerForceClosed":false,"propertyValue_circuitBreakerEnabled":true,"propertyValue_executionIsolationStrategy":"THREAD","propertyValue_executionIsolationThreadTimeoutInMilliseconds":1000,"propertyValue_executionTimeoutInMilliseconds":1000,"propertyValue_executionIsolationThreadInterruptOnTimeout":true,"propertyValue_executionIsolationThreadPoolKeyOverride":null,"propertyValue_executionIsolationSemaphoreMaxConcurrentRequests":10,"propertyValue_fallbackIsolationSemaphoreMaxConcurrentRequests":10,"propertyValue_metricsRollingStatisticalWindowInMilliseconds":10000,"propertyValue_requestCacheEnabled":true,"propertyValue_requestLogEnabled":true,"reportingHosts":1,"threadPool":"service-hi"}

data: {"type":"HystrixThreadPool","name":"service-hi","currentTime":1551319254509,"currentActiveCount":0,"currentCompletedTaskCount":1,"currentCorePoolSize":10,"currentLargestPoolSize":1,"currentMaximumPoolSize":10,"currentPoolSize":1,"currentQueueSize":0,"currentTaskCount":1,"rollingCountThreadsExecuted":0,"rollingMaxActiveThreads":0,"rollingCountCommandRejections":0,"propertyValue_queueSizeRejectionThreshold":5,"propertyValue_metricsRollingStatisticalWindowInMilliseconds":10000,"reportingHosts":1}

如果出現全是ping，那就是沒有先訪問一次服務。

4.Hystrix Dashboard

新建一個名叫servicehystrix的項目，添加pom依賴：

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

啓動類上添加@EnableHystrixDashboard註解，application.yml：

server:
  port: 8000

啓動後訪問localhost:8000/hystrix,可看到如下界面：

將之前整合了Hystrix的服務消費者啓動，在URL一欄輸入localhost:8765/actuator/hystrix.stream,然後填寫一個title，點擊Monitor Stream，可以看到下圖的界面。

5.Turbine聚合監控數據

新建一個serviceturbine項目，pom依賴：

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

啓動類上添加@EnableTurbine註解，

application.yml：

server:
  port: 8001
spring:
  application:
    name: serviceturbine
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
  instance:
    prefer-ip-address: true
turbine:
  app-config: service-ribbon,service-consumer
  cluster-name-expression: "'default'"

再次啓動一個服務消費者(需要整合Actuator並打開hystrix.stream這個斷點)和一個服務提供者，並將服務消費者名稱修改給servi-consumer，服務提供者名稱改爲servicehi，servi-consumer的service層消費servicehi這個服務提供者，這樣就有兩個服務消費者和服務提供者啓動了。這時候啓動servicehystrix和serviceturbine,將兩個服務消費者都訪問幾次，然後訪問localhost:8001/turbine.stream,得到如下：

訪問localhost:8000/hystrix，然後輸入URLlocalhost:8001/turbine.stream，設置一個title點擊Monitor Stream，得到下面的界面：