flink-contrib/flink-connector-wikiedits/src/main/java/org/apache/flink/streaming/connectors/wikiedits/WikipediaEditsSource.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.flink.streaming.connectors.wikiedits;

import org.apache.flink.streaming.api.functions.source.RichSourceFunction;

import java.util.Objects;
import java.util.concurrent.TimeUnit;

/**
 * This class is a SourceFunction that reads {@link WikipediaEditEvent} instances from the IRC
 * channel <code>#en.wikipedia</code>.
 */
public class WikipediaEditsSource extends RichSourceFunction<WikipediaEditEvent> {

    /** Hostname of the server to connect to. */
    public static final String DEFAULT_HOST = "irc.wikimedia.org";

    /** Port of the server to connect to. */
    public static final int DEFAULT_PORT = 6667;

    /** IRC channel to join. */
    public static final String DEFAULT_CHANNEL = "#en.wikipedia";

    private final String host;
    private final int port;
    private final String channel;

    private volatile boolean isRunning = true;

    /**
     * Creates a source reading {@link WikipediaEditEvent} instances from the IRC channel <code>
     * #en.wikipedia</code>.
     *
     * <p>This creates a separate Thread for the IRC connection.
     */
    public WikipediaEditsSource() {
        this(DEFAULT_HOST, DEFAULT_PORT, DEFAULT_CHANNEL);
    }

    /**
     * Creates a source reading {@link WikipediaEditEvent} instances from the specified IRC channel.
     *
     * <p>In most cases, you want to use the default {@link #WikipediaEditsSource} constructor. This
     * constructor is meant to be used only if there is a problem with the default constructor.
     *
     * @param host The IRC server to connect to.
     * @param port The port of the IRC server to connect to.
     * @param channel The channel to join. Messages not matching the expected format will be
     *     ignored.
     */
    public WikipediaEditsSource(String host, int port, String channel) {
        this.host = host;
        this.port = port;
        this.channel = Objects.requireNonNull(channel);
    }

    @Override
    public void run(SourceContext<WikipediaEditEvent> ctx) throws Exception {
        try (WikipediaEditEventIrcStream ircStream = new WikipediaEditEventIrcStream(host, port)) {
            // Open connection and join channel
            ircStream.connect();
            ircStream.join(channel);

            try {
                while (isRunning) {
                    // Query for the next edit event
                    WikipediaEditEvent edit = ircStream.getEdits().poll(100, TimeUnit.MILLISECONDS);

                    if (edit != null) {
                        ctx.collect(edit);
                    }
                }
            } finally {
                ircStream.leave(channel);
            }
        }
    }

    @Override
    public void cancel() {
        isRunning = false;
    }
}