ribbon源码之客户端
客户端模块的核心功能是提供统一的用户请求操作接口。
接口定义
客户端模块的核心是IClient接口，定义了客户端网络请求的方法。
public interface IClient<S extends ClientRequest, T extends IResponse> { public T execute(S request, IClientConfig requestConfig) throws Exception; }
ClientRequest为客户端定义的请求体，存储了请求uri、loadbalancer的key，是否重试、配置。
public class ClientRequest implements Cloneable { protected URI uri; protected Object loadBalancerKey = null; protected Boolean isRetriable = null; protected IClientConfig overrideConfig; }
IResponse为客户端定义的响应内容的接口。
public interface IResponse extends Closeable { public Object getPayload() throws ClientException; public boolean hasPayload(); public boolean isSuccess(); public URI getRequestedURI(); public Map<String, ?> getHeaders(); }
IClientConfigAware定义了需要使用IClientConfig初始化IClient的方法。
public interface IClientConfigAware { public abstract void initWithNiwsConfig(IClientConfig clientConfig); }
ribbon基于http请求，相关类和接口，HttpRequest为http请求；HttpResponse为http请求返回结果；Restclient是基于jesery的IClient实现。
类图
客户端工厂类
客户端模块提供了一个客户端工厂类（ClientFactory）用于通过配置文件来创建IClient实例和负载均衡器（ILoadBalancer）实例。
public static synchronized IClient getNamedClient(String name) {//根据配置获取iclient实例，默认使用DefaultClientConfigImpl配置类。 return getNamedClient(name, DefaultClientConfigImpl.class); }
public static synchronized IClient getNamedClient(String name, Class<? extends IClientConfig> configClass) {
...
return createNamedClient(name, configClass);
...
}
public static synchronized IClient createNamedClient(String name, Class<? extends IClientConfig> configClass) throws ClientException {
IClientConfig config = getNamedConfig(name, configClass);//实例化配置类
return registerClientFromProperties(name, config);//通过配置文件创建iclient
}
public static synchronized ILoadBalancer getNamedLoadBalancer(String name) {
return getNamedLoadBalancer(name, DefaultClientConfigImpl.class);
}
public static synchronized ILoadBalancer getNamedLoadBalancer(String name, Class<? extends IClientConfig> configClass) {
...
lb = registerNamedLoadBalancerFromProperties(name, configClass);
...
}
public static synchronized IClient<?, ?> registerClientFromProperties(String restClientName, IClientConfig clientConfig) throws ClientException { IClient<?, ?> client = null; ILoadBalancer loadBalancer = null; ... String clientClassName = (String) clientConfig.getProperty(CommonClientConfigKey.ClientClassName);//通过配置文件获取client的实现类 client = (IClient<?, ?>) instantiateInstanceWithClientConfig(clientClassName, clientConfig); //通过配置文件创建client实例 boolean initializeNFLoadBalancer = Boolean.parseBoolean(clientConfig.getProperty( CommonClientConfigKey.InitializeNFLoadBalancer, DefaultClientConfigImpl.DEFAULT_ENABLE_LOADBALANCER).toString()); if (initializeNFLoadBalancer) {//如果需要初始化负载均衡器，则通过配置文件创建一个负载均衡器 loadBalancer = registerNamedLoadBalancerFromclientConfig(restClientName, clientConfig); } if (client instanceof AbstractLoadBalancerAwareClient) {//如果client实现AbstractLoadBalancerAwareClient，则注入负载均衡器 ((AbstractLoadBalancerAwareClient) client).setLoadBalancer(loadBalancer); } ...return client; }
public static ILoadBalancer registerNamedLoadBalancerFromclientConfig(String name, IClientConfig clientConfig) throws ClientException {
...
ILoadBalancer lb = null;
...
String loadBalancerClassName = (String) clientConfig.getProperty(CommonClientConfigKey.NFLoadBalancerClassName);//
lb = (ILoadBalancer) ClientFactory.instantiateInstanceWithClientConfig(loadBalancerClassName, clientConfig);
...
return lb;
...
}
//初始化指定的class类
public static Object instantiateInstanceWithClientConfig(String className, IClientConfig clientConfig)
throws InstantiationException, IllegalAccessException, ClassNotFoundException {
Class clazz = Class.forName(className);
if (IClientConfigAware.class.isAssignableFrom(clazz)) {//如果指定的iclient实现了IClientConfigAware，ClientFactory在创建时会使用IClientConfig进行初始化。
IClientConfigAware obj = (IClientConfigAware) clazz.newInstance();
obj.initWithNiwsConfig(clientConfig);
return obj;
} else {
try {
if (clazz.getConstructor(IClientConfig.class) != null) {
return clazz.getConstructor(IClientConfig.class).newInstance(clientConfig);
}
} catch (Throwable e) { // NOPMD
}
}
return clazz.newInstance();
}
使用客户端工厂类（ClientFactory）涉及的配置：
| 属性 | 实现 | 默认值 |
| clientname.ribbon.ClientClassName | client使用的IClient实现类 | com.netflix.niws.client.http.RestClient |
| clientname.ribbon.InitializeNFLoadBalancer | 是否初始化负载均衡器 | true |
| clientname.ribbon.NFLoadBalancerClassName | 负载均衡器的实现类 | com.netflix.loadbalancer.ZoneAwareLoadBalancer |
类图
客户端实现类
AbstractLoadBalancerAwareClient实现了通过负载均衡器进行请求调用。LoadBalancerCommand对负载均衡器操作进行了模版，对请求调用提供了回调函数。
public T executeWithLoadBalancer(final S request, final IClientConfig requestConfig) throws ClientException { LoadBalancerCommand<T> command = buildLoadBalancerCommand(request, requestConfig); ...return command.submit( new ServerOperation<T>() { @Override public Observable<T> call(Server server) { URI finalUri = reconstructURIWithServer(server, request.getUri()); S requestForServer = (S) request.replaceUri(finalUri);//设置最终的调用uri。 try { return Observable.just(AbstractLoadBalancerAwareClient.this.execute(requestForServer, requestConfig)); } //调用execute方法执行请求调用。 catch (Exception e) { return Observable.error(e); } } }) .toBlocking() .single(); ... }
LoadBalancerCommand调用了负载均衡器获得了一个server，然后调用回调函数执行请求。此外还提供了各个关键节点的监听器和异常重试机制。
public Observable<T> submit(final ServerOperation<T> operation) { final ExecutionInfoContext context = new ExecutionInfoContext(); if (listenerInvoker != null) {//执行回调接口 try { listenerInvoker.onExecutionStart(); } catch (AbortExecutionException e) { return Observable.error(e); } } final int maxRetrysSame = retryHandler.getMaxRetriesOnSameServer(); final int maxRetrysNext = retryHandler.getMaxRetriesOnNextServer(); Observable<T> o = (server == null ? selectServer() : Observable.just(server))//调用负载均衡器获得目标server .concatMap(new Func1<Server, Observable<T>>() { ...return operation.call(server).doOnEach(new Observer<T>() { .... }); ... if (maxRetrysSame > 0) o = o.retry(retryPolicy(maxRetrysSame, true)); return o; } }); if (maxRetrysNext > 0 && server == null) o = o.retry(retryPolicy(maxRetrysNext, false)); return o.onErrorResumeNext(new Func1<Throwable, Observable<T>>() { @Override public Observable<T> call(Throwable e) { if (context.getAttemptCount() > 0) { if (maxRetrysNext > 0 && context.getServerAttemptCount() == (maxRetrysNext + 1)) { e = new ClientException(ClientException.ErrorType.NUMBEROF_RETRIES_NEXTSERVER_EXCEEDED, "Number of retries on next server exceeded max " + maxRetrysNext + " retries, while making a call for: " + context.getServer(), e); } else if (maxRetrysSame > 0 && context.getAttemptCount() == (maxRetrysSame + 1)) { e = new ClientException(ClientException.ErrorType.NUMBEROF_RETRIES_EXEEDED, "Number of retries exceeded max " + maxRetrysSame + " retries, while making a call for: " + context.getServer(), e); } } if (listenerInvoker != null) { listenerInvoker.onExecutionFailed(e, context.toFinalExecutionInfo()); } return Observable.error(e); } }); }
private Observable<Server> selectServer() { return Observable.create(new OnSubscribe<Server>() { @Override public void call(Subscriber<? super Server> next) { try { Server server = loadBalancerContext.getServerFromLoadBalancer(loadBalancerURI, loadBalancerKey); next.onNext(server); next.onCompleted(); } catch (Exception e) { next.onError(e); } } }); }
子类 HttpRequest用于http请求，内部定义了http请求的各个内容，并且使用了builder模式。
public class HttpRequest extends ClientRequest {protected CaseInsensitiveMultiMap httpHeaders = new CaseInsensitiveMultiMap();//head参数
protected Multimap<String, String> queryParams = ArrayListMultimap.create();//query参数
private Object entity;／／消息体
protected Verb verb;//http请求的method：post get head delete等。默认get
}
类图
