Java tutorial
/*********************************************************************************************************************** * 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; } }