聊聊netflix的EurekaHttpClient

序

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();
}

能夠看到這個client接口定義了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經過定義一個抽象方法execute(RequestExecutor<R> requestExecutor)，來包裝EurekaHttpClient

EurekaHttpClientDecorator的子類

繼承自EurekaHttpClientDecorator的類有以下幾個，都在com.netflix.discovery.shared.transport.decorator包裏頭

• 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();

}

這個是EurekaHttpClient的工廠高級別接口，定義了newClient()以及shutdown()方法

EurekaHttpClientFactory的實現類

• 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();
            }
        };
    }

建立的是通過RetryableEurekaHttpClient包裝的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();
            }
        };
    }

建立的是通過MetricsCollectingEurekaHttpClient包裝的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();
            }
        };
    }

建立的是通過RedirectingEurekaHttpClient、RetryableEurekaHttpClient、SessionedEurekaHttpClient包裝以後的client
而原始的EurekaHttpClient則經過TransportClientFactory建立

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();

}

如註釋上所說，不建議高級別的消費者使用，是一個低級別的api

TransportClientFactory實現類

• 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

上面這三個是有專門的類實現，下面這幾個是匿名類實現

• RedirectingEurekaHttpClient
• EurekaServerHttpClients
• Jersey1TransportClientFactories
• MetricsCollectingEurekaHttpClient

小結

netflix的eureka關於httpClient的接口爲EurekaHttpClient，其工廠方法主要分類top level的EurekaHttpClientFactory以及low level的TransportClientFactory。

• top level的話，主要是經過decorator模式進行一系列包裝，像EurekaHttpClients建立的則是通過RedirectingEurekaHttpClient、RetryableEurekaHttpClient、SessionedEurekaHttpClient包裝的client。
• low levle的話，主要是底層的http遠程調用的實現，netflix提供的是基於Jersey的版本，而spring cloud則提供了基於RestTemplate的版本。

doc

• EurekaHttpClient