聊聊netflix的EurekaHttpClient-白红宇

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本文主要研究下netflix的EurekaHttpClient

EurekaHttpClient

eureka-client-1.8.8-sources.jar!/com/netflix/discovery/shared/transport/EurekaHttpClient.java

public interface EurekaHttpClient {    EurekaHttpResponse
    
      register(InstanceInfo info);    EurekaHttpResponse
     
       cancel(String appName, String id);    EurekaHttpResponse
      
        sendHeartBeat(String appName, String id, InstanceInfo info, InstanceStatus overriddenStatus);    EurekaHttpResponse
       
         statusUpdate(String appName, String id, InstanceStatus newStatus, InstanceInfo info);    EurekaHttpResponse
        
          deleteStatusOverride(String appName, String id, InstanceInfo info);    EurekaHttpResponse
         
           getApplications(String... regions); EurekaHttpResponse
          
            getDelta(String... regions); EurekaHttpResponse
           
             getVip(String vipAddress, String... regions); EurekaHttpResponse
            
              getSecureVip(String secureVipAddress, String... regions); EurekaHttpResponse
             
               getApplication(String appName); EurekaHttpResponse
              
                getInstance(String appName, String id); EurekaHttpResponse
               
                 getInstance(String id); void shutdown();}复制代码

可以看到这个client接口定义了eureka server的一些low level rest api，其中包括register、cancel、sendHeartBeat、statusUpdate、getApplications等。

EurekaHttpClientDecorator

eureka-client-1.8.8-sources.jar!/com/netflix/discovery/shared/transport/decorator/EurekaHttpClientDecorator.java

public abstract class EurekaHttpClientDecorator implements EurekaHttpClient {    public enum RequestType {        Register,        Cancel,        SendHeartBeat,        StatusUpdate,        DeleteStatusOverride,        GetApplications,        GetDelta,        GetVip,        GetSecureVip,        GetApplication,        GetInstance,        GetApplicationInstance    }    public interface RequestExecutor
    
      {        EurekaHttpResponse
     
       execute(EurekaHttpClient delegate);        RequestType getRequestType();    }    protected abstract 
      
        EurekaHttpResponse
       
         execute(RequestExecutor
        
          requestExecutor);    //......}复制代码

EurekaHttpClientDecorator通过定义一个抽象方法execute(RequestExecutor requestExecutor)，来包装EurekaHttpClient

EurekaHttpClientDecorator的子类

继承自EurekaHttpClientDecorator的类有如下几个，都在com.netflix.discovery.shared.transport.decorator包里头

MetricsCollectingEurekaHttpClient

RedirectingEurekaHttpClient

RetryableEurekaHttpClient

SessionedEurekaHttpClient

EurekaHttpClientFactory(`top level`)

eureka-client-1.8.8-sources.jar!/com/netflix/discovery/shared/transport/EurekaHttpClientFactory.java

/** * A top level factory to create http clients for application/eurekaClient use * * @author Tomasz Bak */public interface EurekaHttpClientFactory {    EurekaHttpClient newClient();    void shutdown();}复制代码

这个是EurekaHttpClient的工厂高级别接口，定义了newClient()以及shutdown()方法

EurekaHttpClientFactory的实现类

RetryableEurekaHttpClient eureka-client-1.8.8-sources.jar!/com/netflix/discovery/shared/transport/decorator/RetryableEurekaHttpClient.java

public static EurekaHttpClientFactory createFactory(final String name,                                                        final EurekaTransportConfig transportConfig,                                                        final ClusterResolver
    
      clusterResolver,                                                        final TransportClientFactory delegateFactory,                                                        final ServerStatusEvaluator serverStatusEvaluator) {        return new EurekaHttpClientFactory() {            @Override            public EurekaHttpClient newClient() {                return new RetryableEurekaHttpClient(name, transportConfig, clusterResolver, delegateFactory,                        serverStatusEvaluator, DEFAULT_NUMBER_OF_RETRIES);            }            @Override            public void shutdown() {                delegateFactory.shutdown();            }        };    }复制代码

创建的是经过RetryableEurekaHttpClient包装的client

MetricsCollectingEurekaHttpClient eureka-client-1.8.8-sources.jar!/com/netflix/discovery/shared/transport/decorator/MetricsCollectingEurekaHttpClient.java

public static EurekaHttpClientFactory createFactory(final EurekaHttpClientFactory delegateFactory) {        final Map
    
      metricsByRequestType = initializeMetrics();        final ExceptionsMetric exceptionMetrics = new ExceptionsMetric(EurekaClientNames.METRIC_TRANSPORT_PREFIX + "exceptions");        return new EurekaHttpClientFactory() {            @Override            public EurekaHttpClient newClient() {                return new MetricsCollectingEurekaHttpClient(                        delegateFactory.newClient(),                        metricsByRequestType,                        exceptionMetrics,                        false                );            }            @Override            public void shutdown() {                shutdownMetrics(metricsByRequestType);                exceptionMetrics.shutdown();            }        };    }复制代码

创建的是经过MetricsCollectingEurekaHttpClient包装的client

EurekaHttpClients eureka-client-1.8.8-sources.jar!/com/netflix/discovery/shared/transport/EurekaHttpClients.java

static EurekaHttpClientFactory canonicalClientFactory(final String name,                                                          final EurekaTransportConfig transportConfig,                                                          final ClusterResolver
    
      clusterResolver,                                                          final TransportClientFactory transportClientFactory) {        return new EurekaHttpClientFactory() {            @Override            public EurekaHttpClient newClient() {                return new SessionedEurekaHttpClient(                        name,                        RetryableEurekaHttpClient.createFactory(                                name,                                transportConfig,                                clusterResolver,                                RedirectingEurekaHttpClient.createFactory(transportClientFactory),                                ServerStatusEvaluators.legacyEvaluator()),                        transportConfig.getSessionedClientReconnectIntervalSeconds() * 1000                );            }            @Override            public void shutdown() {                wrapClosable(clusterResolver).shutdown();            }        };    }复制代码

创建的是经过RedirectingEurekaHttpClient、RetryableEurekaHttpClient、SessionedEurekaHttpClient包装之后的client 而原始的EurekaHttpClient则通过TransportClientFactory创建

TransportClientFactory(`low level`)

eureka-client-1.8.8-sources.jar!/com/netflix/discovery/shared/transport/TransportClientFactory.java

/** * A low level client factory interface. Not advised to be used by top level consumers. * * @author David Liu */public interface TransportClientFactory {    EurekaHttpClient newClient(EurekaEndpoint serviceUrl);    void shutdown();}复制代码

如注释上所说，不建议高级别的消费者使用，是一个低级别的api

TransportClientFactory实现类

JerseyEurekaHttpClientFactory eureka-client-1.8.8-sources.jar!/com/netflix/discovery/shared/transport/jersey/JerseyEurekaHttpClientFactory.java

JerseyRemoteRegionClientFactory eureka-core-1.8.8-sources.jar!/com/netflix/eureka/transport/JerseyRemoteRegionClientFactory.java

RestTemplateTransportClientFactory spring-cloud-netflix-eureka-client-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/http/RestTemplateTransportClientFactory.java

上面这三个是有专门的类实现，下面这几个是匿名类实现

RedirectingEurekaHttpClient

EurekaServerHttpClients

Jersey1TransportClientFactories

MetricsCollectingEurekaHttpClient

小结

netflix的eureka关于httpClient的接口为EurekaHttpClient，其工厂方法主要分类top level的EurekaHttpClientFactory以及low level的TransportClientFactory。

top level的话，主要是通过decorator模式进行一系列包装，像EurekaHttpClients创建的则是经过RedirectingEurekaHttpClient、RetryableEurekaHttpClient、SessionedEurekaHttpClient包装的client。

low levle的话，主要是底层的http远程调用的实现，netflix提供的是基于Jersey的版本，而spring cloud则提供了基于RestTemplate的版本。

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