MessagingClient.java

/*
 * Copyright 2015 Netflix, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
package io.reactivex.netty.examples.http.ws.messaging;

import io.netty.handler.codec.http.websocketx.BinaryWebSocketFrame;
import io.netty.handler.codec.http.websocketx.WebSocketFrame;
import io.netty.handler.logging.LogLevel;
import io.reactivex.netty.examples.ExamplesEnvironment;
import io.reactivex.netty.protocol.http.client.HttpClient;
import io.reactivex.netty.protocol.http.ws.client.WebSocketResponse;
import org.slf4j.Logger;
import rx.Observable;

import java.io.IOException;
import java.net.SocketAddress;
import java.util.concurrent.TimeUnit;

/**
 * An example to demonstrate how to use WebSocket to send messages to a messaging server.
 * This example sends a stream of 10 {@link MessageFrame} to the specified server and expects 10 acknowledgments in
 * response.
 *
 * There are three ways of running this example:
 *
 * <h2>Default</h2>
 *
 * The default way is to just run this class with no arguments, which will start a server ({@link MessagingServer})
 * on an ephemeral port and then send an HTTP request to that server and print the response.
 *
 * <h2>After starting {@link MessagingServer}</h2>
 *
 * If you want to see how {@link MessagingServer} work, you can run {@link MessagingServer} by yourself and
 * then pass the port on which the server started to this class as a program argument:
 *
 <PRE>
 java io.reactivex.netty.examples.http.ws.messaging.MessagingClient [server port]
 </PRE>
 *
 * <h2>Existing HTTP server</h2>
 *
 * You can also use this client to send a GET request "/ws" to an existing HTTP server (different than
 * {@link MessagingServer}) by passing the port and host of the existing server similar to the case above:
 *
 <PRE>
 java io.reactivex.netty.examples.http.ws.messaging.MessagingClient [server port]
 </PRE>
 * If the server host is omitted from the above, it defaults to "127.0.0.1"
 *
 * In all the above usages, this client will print the response received from the server.
 *
 * <h2>Retry</h2>
 *
 * If the client does not receive acknowledgments for any message ID for 10 seconds, it re-sends the message. See
 * {@link PendingMessageTracker} for the relevant code.
 * This means that this example follows the atleast once delivery semantics.
 *
 * <h2>Message buffering</h2>
 *
 * Since, message production is asynchronous, if this client can not connect to the server, it will buffer the messages
 * in memory and wait for the server to come up.
 */
public final class MessagingClient {

    public static void main(String[] args) {

        ExamplesEnvironment env = ExamplesEnvironment.newEnvironment(MessagingClient.class);
        /*
         * Retrieves the server address, using the following algorithm:
         * <ul>
             <li>If any arguments are passed, then use the first argument as the server port.</li>
             <li>If available, use the second argument as the server host, else default to localhost</li>
             <li>Otherwise, start the passed server class and use that address.</li>
         </ul>
         */
        SocketAddress socketAddress = env.getServerAddress(MessagingServer.class, args);
        Logger logger = env.getLogger();

        /*Sends 10 messages each at an interval of 10 seconds to show asynchronous message creation*/
        MessageProducer producer = new MessageProducer(10, 1, TimeUnit.SECONDS);

        /*Create a new client for the server address*/
        HttpClient.newClient(socketAddress)
                  .enableWireLogging("msging-client", LogLevel.DEBUG)
                  .createGet("/ws")
                  .requestWebSocketUpgrade()
                  .doOnNext(resp -> logger.info(resp.toString()))
                  .flatMap(WebSocketResponse::getWebSocketConnection)
                  .flatMap(conn ->
                                   conn.writeAndFlushOnEach(producer.getMessageStream())
                                       .cast(WebSocketFrame.class)
                                       .mergeWith(conn.getInput())
                  )
                  .retryWhen(errStream -> errStream.flatMap(err -> {
                      if (err instanceof IOException) {
                          return Observable.timer(1, TimeUnit.SECONDS);
                      }
                      return Observable.error(err);
                  }))
                  .filter(AcceptOnlyBinaryFramesFilter.INSTANCE)
                  .cast(BinaryWebSocketFrame.class)
                  .map(producer::acceptAcknowledgment)
                  .take(10)
                  .toBlocking()
                  .forEach(msgId -> logger.info("Received acknowledgment for message id => " + msgId.toString()));
    }
}