eu.stratosphere.nephele.io.RuntimeInputGate.java Source code

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/***********************************************************************************************************************
 * Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
 *
 * 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 eu.stratosphere.nephele.io;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import eu.stratosphere.core.io.IOReadableWritable;
import eu.stratosphere.nephele.event.task.AbstractEvent;
import eu.stratosphere.nephele.event.task.AbstractTaskEvent;
import eu.stratosphere.nephele.io.channels.AbstractInputChannel;
import eu.stratosphere.nephele.io.channels.ChannelID;
import eu.stratosphere.nephele.io.channels.bytebuffered.InMemoryInputChannel;
import eu.stratosphere.nephele.io.channels.bytebuffered.NetworkInputChannel;
import eu.stratosphere.nephele.jobgraph.JobID;

/**
 * In Nephele input gates are a specialization of general gates and connect input channels and record readers. As
 * channels, input gates are always parameterized to a specific type of record which they can transport. In contrast to
 * output gates input gates can be associated with a {@link DistributionPattern} object which dictates the concrete
 * wiring between two groups of vertices.
 * 
 * @param <T> The type of record that can be transported through this gate.
 */
public class RuntimeInputGate<T extends IOReadableWritable> extends AbstractGate<T> implements InputGate<T> {

    /**
     * The log object used for debugging.
     */
    private static final Log LOG = LogFactory.getLog(InputGate.class);

    /**
     * The deserializer factory used to instantiate the deserializers that construct records from byte streams.
     */
    private final RecordDeserializerFactory<T> deserializerFactory;

    /**
     * The list of input channels attached to this input gate.
     */
    private final ArrayList<AbstractInputChannel<T>> inputChannels = new ArrayList<AbstractInputChannel<T>>();

    /**
     * Queue with indices of channels that store at least one available record.
     */
    private final BlockingQueue<Integer> availableChannels = new LinkedBlockingQueue<Integer>();

    /**
     * The listener object to be notified when a channel has at least one record available.
     */
    private final AtomicReference<RecordAvailabilityListener<T>> recordAvailabilityListener = new AtomicReference<RecordAvailabilityListener<T>>(
            null);

    private AbstractTaskEvent currentEvent;

    /**
     * If the value of this variable is set to <code>true</code>, the input gate is closed.
     */
    private boolean isClosed = false;

    /**
     * The channel to read from next.
     */
    private int channelToReadFrom = -1;

    /**
     * Constructs a new runtime input gate.
     * 
     * @param jobID
     *        the ID of the job this input gate belongs to
     * @param gateID
     *        the ID of the gate
     * @param deserializerFactory
     *        The factory used to instantiate the deserializers that construct records from byte streams.
     * @param index
     *        the index assigned to this input gate at the {@link Environment} object
     */
    public RuntimeInputGate(final JobID jobID, final GateID gateID,
            final RecordDeserializerFactory<T> deserializerFactory, final int index) {
        super(jobID, gateID, index);
        this.deserializerFactory = deserializerFactory;
    }

    /**
     * Adds a new input channel to the input gate.
     * 
     * @param inputChannel
     *        the input channel to be added.
     */
    private void addInputChannel(AbstractInputChannel<T> inputChannel) {
        // in high DOPs, this can be a serious performance issue, as adding all channels and checking linearly has a
        // quadratic complexity!
        if (!this.inputChannels.contains(inputChannel)) {
            this.inputChannels.add(inputChannel);
        }
    }

    /**
     * Removes the input channel with the given ID from the input gate if it exists.
     * 
     * @param inputChannelID
     *        the ID of the channel to be removed
     */
    public void removeInputChannel(ChannelID inputChannelID) {

        for (int i = 0; i < this.inputChannels.size(); i++) {

            final AbstractInputChannel<T> inputChannel = this.inputChannels.get(i);
            if (inputChannel.getID().equals(inputChannelID)) {
                this.inputChannels.remove(i);
                return;
            }
        }

        if (LOG.isDebugEnabled()) {
            LOG.debug("Cannot find output channel with ID " + inputChannelID + " to remove");
        }
    }

    @Override
    public boolean isInputGate() {
        return true;
    }

    @Override
    public int getNumberOfInputChannels() {
        return this.inputChannels.size();
    }

    @Override
    public AbstractInputChannel<T> getInputChannel(int pos) {
        return this.inputChannels.get(pos);
    }

    @Override
    public NetworkInputChannel<T> createNetworkInputChannel(final InputGate<T> inputGate, final ChannelID channelID,
            final ChannelID connectedChannelID) {

        final NetworkInputChannel<T> enic = new NetworkInputChannel<T>(inputGate, this.inputChannels.size(),
                this.deserializerFactory.createDeserializer(), channelID, connectedChannelID);
        addInputChannel(enic);

        return enic;
    }

    @Override
    public InMemoryInputChannel<T> createInMemoryInputChannel(final InputGate<T> inputGate,
            final ChannelID channelID, final ChannelID connectedChannelID) {

        final InMemoryInputChannel<T> eimic = new InMemoryInputChannel<T>(inputGate, this.inputChannels.size(),
                this.deserializerFactory.createDeserializer(), channelID, connectedChannelID);
        addInputChannel(eimic);

        return eimic;
    }

    @Override
    public InputChannelResult readRecord(T target) throws IOException, InterruptedException {

        if (this.channelToReadFrom == -1) {
            if (this.isClosed()) {
                return InputChannelResult.END_OF_STREAM;
            }

            if (Thread.interrupted()) {
                throw new InterruptedException();
            }

            this.channelToReadFrom = waitForAnyChannelToBecomeAvailable();
        }

        InputChannelResult result = this.getInputChannel(this.channelToReadFrom).readRecord(target);
        switch (result) {
        case INTERMEDIATE_RECORD_FROM_BUFFER: // full record and we can stay on the same channel
            return InputChannelResult.INTERMEDIATE_RECORD_FROM_BUFFER;

        case LAST_RECORD_FROM_BUFFER: // full record, but we must switch the channel afterwards
            this.channelToReadFrom = -1;
            return InputChannelResult.LAST_RECORD_FROM_BUFFER;

        case END_OF_SUPERSTEP:
            this.channelToReadFrom = -1;
            return InputChannelResult.END_OF_SUPERSTEP;

        case TASK_EVENT: // task event
            this.currentEvent = this.getInputChannel(this.channelToReadFrom).getCurrentEvent();
            this.channelToReadFrom = -1; // event always marks a unit as consumed
            return InputChannelResult.TASK_EVENT;

        case NONE: // internal event or an incomplete record that needs further chunks
            // the current unit is exhausted
            this.channelToReadFrom = -1;
            return InputChannelResult.NONE;

        case END_OF_STREAM: // channel is done
            this.channelToReadFrom = -1;
            return isClosed() ? InputChannelResult.END_OF_STREAM : InputChannelResult.NONE;

        default: // silence the compiler
            throw new RuntimeException();
        }
    }

    @Override
    public AbstractTaskEvent getCurrentEvent() {
        AbstractTaskEvent e = this.currentEvent;
        this.currentEvent = null;
        return e;
    }

    @Override
    public void notifyRecordIsAvailable(int channelIndex) {
        this.availableChannels.add(Integer.valueOf(channelIndex));

        RecordAvailabilityListener<T> listener = this.recordAvailabilityListener.get();
        if (listener != null) {
            listener.reportRecordAvailability(this);
        }
    }

    /**
     * This method returns the index of a channel which has at least
     * one record available. The method may block until at least one
     * channel has become ready.
     * 
     * @return the index of the channel which has at least one record available
     */
    public int waitForAnyChannelToBecomeAvailable() throws InterruptedException {
        return this.availableChannels.take().intValue();
    }

    @Override
    public boolean isClosed() throws IOException, InterruptedException {

        if (this.isClosed) {
            return true;
        }

        for (int i = 0; i < this.getNumberOfInputChannels(); i++) {
            final AbstractInputChannel<T> inputChannel = this.inputChannels.get(i);
            if (!inputChannel.isClosed()) {
                return false;
            }
        }

        this.isClosed = true;

        return true;
    }

    @Override
    public void close() throws IOException, InterruptedException {

        for (int i = 0; i < this.getNumberOfInputChannels(); i++) {
            final AbstractInputChannel<T> inputChannel = this.inputChannels.get(i);
            inputChannel.close();
        }

    }

    @Override
    public String toString() {
        return "Input " + super.toString();
    }

    @Override
    public void publishEvent(AbstractEvent event) throws IOException, InterruptedException {

        // Copy event to all connected channels
        final Iterator<AbstractInputChannel<T>> it = this.inputChannels.iterator();
        while (it.hasNext()) {
            it.next().transferEvent(event);
        }
    }

    /**
     * Returns the {@link RecordDeserializerFactory} used by this input gate.
     * 
     * @return The {@link RecordDeserializerFactory} used by this input gate.
     */
    public RecordDeserializerFactory<T> getRecordDeserializerFactory() {
        return this.deserializerFactory;
    }

    @Override
    public void releaseAllChannelResources() {

        final Iterator<AbstractInputChannel<T>> it = this.inputChannels.iterator();
        while (it.hasNext()) {
            it.next().releaseAllResources();
        }
    }

    @Override
    public void registerRecordAvailabilityListener(final RecordAvailabilityListener<T> listener) {
        if (!this.recordAvailabilityListener.compareAndSet(null, listener)) {
            throw new IllegalStateException(
                    this.recordAvailabilityListener + " is already registered as a record availability listener");
        }
    }

    public void notifyDataUnitConsumed(int channelIndex) {
        this.channelToReadFrom = -1;
    }
}