聊聊netflix的EurekaHttpClient

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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<Void> register(InstanceInfo info);

    EurekaHttpResponse<Void> cancel(String appName, String id);

    EurekaHttpResponse<InstanceInfo> sendHeartBeat(String appName, String id, InstanceInfo info, InstanceStatus overriddenStatus);

    EurekaHttpResponse<Void> statusUpdate(String appName, String id, InstanceStatus newStatus, InstanceInfo info);

    EurekaHttpResponse<Void> deleteStatusOverride(String appName, String id, InstanceInfo info);

    EurekaHttpResponse<Applications> getApplications(String... regions);

    EurekaHttpResponse<Applications> getDelta(String... regions);

    EurekaHttpResponse<Applications> getVip(String vipAddress, String... regions);

    EurekaHttpResponse<Applications> getSecureVip(String secureVipAddress, String... regions);

    EurekaHttpResponse<Application> getApplication(String appName);

    EurekaHttpResponse<InstanceInfo> getInstance(String appName, String id);

    EurekaHttpResponse<InstanceInfo> getInstance(String id);

    void shutdown();
}

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<R> {
        EurekaHttpResponse<R> execute(EurekaHttpClient delegate);

        RequestType getRequestType();
    }

    protected abstract <R> EurekaHttpResponse<R> execute(RequestExecutor<R> requestExecutor);

    //......
}

EurekaHttpClientDecorator通过定义一个抽象方法execute(RequestExecutorrequestExecutor)，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();

}

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<EurekaEndpoint> 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(); } }; } 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<RequestType, EurekaHttpClientRequestMetrics> 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(); } }; } 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<EurekaEndpoint> 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(); } }; } 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();

}

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。

doc

• EurekaHttpClient