/*
* 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.runtime.operators;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.metrics.Counter;
import org.apache.flink.runtime.operators.util.metrics.CountingCollector;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.flink.api.common.functions.ReduceFunction;
import org.apache.flink.api.common.typeutils.TypeComparator;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.runtime.operators.util.TaskConfig;
import org.apache.flink.util.Collector;
import org.apache.flink.util.MutableObjectIterator;
/**
* Reduce driver which is executed by a Task Manager. The task has a
* single input and one or multiple outputs. It is provided with a ReduceFunction
* implementation.
* <p>
* The ReduceDriver creates an iterator over all records from its input. The iterator returns all records grouped by their
* key. The elements are handed pairwise to the <code>reduce()</code> method of the ReduceFunction.
*
* @see org.apache.flink.api.common.functions.ReduceFunction
*/
public class ReduceDriver<T> implements Driver<ReduceFunction<T>, T> {
private static final Logger LOG = LoggerFactory.getLogger(ReduceDriver.class);
private TaskContext<ReduceFunction<T>, T> taskContext;
private MutableObjectIterator<T> input;
private TypeSerializer<T> serializer;
private TypeComparator<T> comparator;
private volatile boolean running;
private boolean objectReuseEnabled = false;
// ------------------------------------------------------------------------
@Override
public void setup(TaskContext<ReduceFunction<T>, T> context) {
this.taskContext = context;
this.running = true;
}
@Override
public int getNumberOfInputs() {
return 1;
}
@Override
public Class<ReduceFunction<T>> getStubType() {
@SuppressWarnings("unchecked")
final Class<ReduceFunction<T>> clazz = (Class<ReduceFunction<T>>) (Class<?>) ReduceFunction.class;
return clazz;
}
@Override
public int getNumberOfDriverComparators() {
return 1;
}
// --------------------------------------------------------------------------------------------
@Override
public void prepare() throws Exception {
TaskConfig config = this.taskContext.getTaskConfig();
if (config.getDriverStrategy() != DriverStrategy.SORTED_REDUCE) {
throw new Exception("Unrecognized driver strategy for Reduce driver: " + config.getDriverStrategy().name());
}
this.serializer = this.taskContext.<T>getInputSerializer(0).getSerializer();
this.comparator = this.taskContext.getDriverComparator(0);
this.input = this.taskContext.getInput(0);
ExecutionConfig executionConfig = taskContext.getExecutionConfig();
this.objectReuseEnabled = executionConfig.isObjectReuseEnabled();
if (LOG.isDebugEnabled()) {
LOG.debug("ReduceDriver object reuse: " + (this.objectReuseEnabled ? "ENABLED" : "DISABLED") + ".");
}
}
@Override
public void run() throws Exception {
if (LOG.isDebugEnabled()) {
LOG.debug(this.taskContext.formatLogString("Reducer preprocessing done. Running Reducer code."));
}
final Counter numRecordsIn = this.taskContext.getMetricGroup().getIOMetricGroup().getNumRecordsInCounter();
final Counter numRecordsOut = this.taskContext.getMetricGroup().getIOMetricGroup().getNumRecordsOutCounter();
// cache references on the stack
final MutableObjectIterator<T> input = this.input;
final TypeSerializer<T> serializer = this.serializer;
final TypeComparator<T> comparator = this.comparator;
final ReduceFunction<T> function = this.taskContext.getStub();
final Collector<T> output = new CountingCollector<>(this.taskContext.getOutputCollector(), numRecordsOut);
if (objectReuseEnabled) {
// We only need two objects. The first reference stores results and is
// eventually collected. New values are read into the second.
//
// The output value must have the same key fields as the input values.
T reuse1 = input.next();
T reuse2 = serializer.createInstance();
T value = reuse1;
// iterate over key groups
while (this.running && value != null) {
numRecordsIn.inc();
comparator.setReference(value);
// iterate within a key group
while ((reuse2 = input.next(reuse2)) != null) {
numRecordsIn.inc();
if (comparator.equalToReference(reuse2)) {
// same group, reduce
value = function.reduce(value, reuse2);
// we must never read into the object returned
// by the user, so swap the reuse objects
if (value == reuse2) {
T tmp = reuse1;
reuse1 = reuse2;
reuse2 = tmp;
}
} else {
// new key group
break;
}
}
output.collect(value);
// swap the value from the new key group into the first object
T tmp = reuse1;
reuse1 = reuse2;
reuse2 = tmp;
value = reuse1;
}
} else {
T value = input.next();
// iterate over key groups
while (this.running && value != null) {
numRecordsIn.inc();
comparator.setReference(value);
T res = value;
// iterate within a key group
while ((value = input.next()) != null) {
numRecordsIn.inc();
if (comparator.equalToReference(value)) {
// same group, reduce
res = function.reduce(res, value);
} else {
// new key group
break;
}
}
output.collect(res);
}
}
}
@Override
public void cleanup() {}
@Override
public void cancel() {
this.running = false;
}
}