flink-streaming-java/src/main/java/org/apache/flink/streaming/experimental/CollectSink.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.experimental;

import org.apache.flink.annotation.Experimental;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
import org.apache.flink.streaming.api.functions.sink.RichSinkFunction;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;

/**
 * A specialized data sink to be used by DataStreamUtils.collect().
 *
 * <p>This experimental class is relocated from flink-streaming-contrib. Please see
 * package-info.java for more information.
 */
@Experimental
public class CollectSink<IN> extends RichSinkFunction<IN> {

    private static final long serialVersionUID = 1L;

    private final InetAddress hostIp;
    private final int port;
    private final TypeSerializer<IN> serializer;

    private transient Socket client;
    private transient OutputStream outputStream;
    private transient DataOutputViewStreamWrapper streamWriter;

    /**
     * Creates a CollectSink that will send the data to the specified host.
     *
     * @param hostIp IP address of the Socket server.
     * @param port Port of the Socket server.
     * @param serializer A serializer for the data.
     */
    public CollectSink(InetAddress hostIp, int port, TypeSerializer<IN> serializer) {
        this.hostIp = hostIp;
        this.port = port;
        this.serializer = serializer;
    }

    @Override
    public void invoke(IN value, Context context) throws Exception {
        try {
            serializer.serialize(value, streamWriter);
        } catch (Exception e) {
            throw new IOException(
                    "Error sending data back to client (" + hostIp.toString() + ":" + port + ')',
                    e);
        }
    }

    /**
     * Initialize the connection with the Socket in the server.
     *
     * @param parameters Configuration.
     */
    @Override
    public void open(Configuration parameters) throws Exception {
        try {
            client = new Socket(hostIp, port);
            outputStream = client.getOutputStream();
            streamWriter = new DataOutputViewStreamWrapper(outputStream);
        } catch (IOException e) {
            throw new IOException(
                    "Cannot get back the stream while opening connection to client at "
                            + hostIp.toString()
                            + ":"
                            + port,
                    e);
        }
    }

    /** Closes the connection with the Socket server. */
    @Override
    public void close() throws Exception {
        try {
            if (outputStream != null) {
                outputStream.flush();
                outputStream.close();
            }

            // first regular attempt to cleanly close. Failing that will escalate
            if (client != null) {
                client.close();
            }
        } catch (Exception e) {
            throw new IOException(
                    "Error while closing connection that streams data back to client at "
                            + hostIp.toString()
                            + ":"
                            + port,
                    e);
        } finally {
            // if we failed prior to closing the client, close it
            if (client != null) {
                try {
                    client.close();
                } catch (Throwable t) {
                    // best effort to close, we do not care about an exception here any more
                }
            }
        }
    }
}