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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(RequestExecutor<R> 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<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。
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