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 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();
}

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);

    //......
}

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();

}

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();
            }
        };
    }

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();
            }
        };
    }

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();
            }
        };
    }

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