/***********************************************************************************************************************
* 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.pact.runtime.task;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import eu.stratosphere.api.common.functions.GenericReduce;
import eu.stratosphere.api.common.typeutils.TypeSerializer;
import eu.stratosphere.api.common.typeutils.TypeSerializerFactory;
import eu.stratosphere.pact.runtime.task.util.TaskConfig;
import eu.stratosphere.util.MutableObjectIterator;
/**
* Reduce task which is executed by a Nephele task manager. The task has a
* single input and one or multiple outputs. It is provided with a ReduceFunction
* implementation.
* <p>
* The ReduceTask creates a iterator over all records from its input. The iterator returns all records grouped by their
* key. The iterator is handed to the <code>reduce()</code> method of the ReduceFunction.
*
* @see GenericReduce
*/
public class AllReduceDriver<T> implements PactDriver<GenericReduce<T>, T> {
private static final Log LOG = LogFactory.getLog(AllReduceDriver.class);
private PactTaskContext<GenericReduce<T>, T> taskContext;
private MutableObjectIterator<T> input;
private TypeSerializer<T> serializer;
private boolean running;
// ------------------------------------------------------------------------
@Override
public void setup(PactTaskContext<GenericReduce<T>, T> context) {
this.taskContext = context;
this.running = true;
}
@Override
public int getNumberOfInputs() {
return 1;
}
@Override
public Class<GenericReduce<T>> getStubType() {
@SuppressWarnings("unchecked")
final Class<GenericReduce<T>> clazz = (Class<GenericReduce<T>>) (Class<?>) GenericReduce.class;
return clazz;
}
@Override
public boolean requiresComparatorOnInput() {
return false;
}
// --------------------------------------------------------------------------------------------
@Override
public void prepare() throws Exception {
final TaskConfig config = this.taskContext.getTaskConfig();
if (config.getDriverStrategy() != DriverStrategy.ALL_REDUCE) {
throw new Exception("Unrecognized driver strategy for AllReduce driver: " + config.getDriverStrategy().name());
}
TypeSerializerFactory<T> serializerFactory = this.taskContext.getInputSerializer(0);
this.serializer = serializerFactory.getSerializer();
this.input = this.taskContext.getInput(0);
}
@Override
public void run() throws Exception {
if (LOG.isDebugEnabled()) {
LOG.debug(this.taskContext.formatLogString("AllReduce preprocessing done. Running Reducer code."));
}
final GenericReduce<T> stub = this.taskContext.getStub();
final MutableObjectIterator<T> input = this.input;
final TypeSerializer<T> serializer = this.serializer;
T val1 = serializer.createInstance();
if ((val1 = input.next(val1)) == null) {
return;
}
T val2;
while (running && (val2 = input.next(serializer.createInstance())) != null) {
val1 = stub.reduce(val1, val2);
}
this.taskContext.getOutputCollector().collect(val1);
}
@Override
public void cleanup() {}
@Override
public void cancel() {
this.running = false;
}
}