/*
* 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.api.common.functions.GroupCombineFunction;
import org.apache.flink.api.common.typeutils.TypeComparator;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.common.typeutils.TypeSerializerFactory;
import org.apache.flink.core.memory.MemorySegment;
import org.apache.flink.runtime.memory.MemoryManager;
import org.apache.flink.runtime.operators.sort.FixedLengthRecordSorter;
import org.apache.flink.runtime.operators.sort.InMemorySorter;
import org.apache.flink.runtime.operators.sort.NormalizedKeySorter;
import org.apache.flink.runtime.operators.sort.QuickSort;
import org.apache.flink.runtime.util.NonReusingKeyGroupedIterator;
import org.apache.flink.runtime.util.ReusingKeyGroupedIterator;
import org.apache.flink.util.Collector;
import org.apache.flink.util.MutableObjectIterator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Collections;
import java.util.List;
/**
* Non-chained combine driver which is used for a CombineGroup transformation or a GroupReduce transformation where
* the user supplied a RichGroupReduceFunction with a combine method. The combining is performed in memory with a
* lazy approach which only combines elements which currently fit in the sorter. This may lead to a partial solution.
* In the case of the RichGroupReduceFunction this partial result is transformed into a proper deterministic result.
* The CombineGroup uses the GroupCombineFunction interface which allows to combine values of type {@code IN}
* to any type of type {@code OUT}. In contrast, the RichGroupReduceFunction requires the combine method
* to have the same input and output type to be able to reduce the elements after the combine from
* {@code IN} to {@code OUT}.
*
* <p>The GroupReduceCombineDriver uses a combining iterator over its input. The output of the iterator is emitted.</p>
*
* @param <IN> The data type consumed by the combiner.
* @param <OUT> The data type produced by the combiner.
*/
public class GroupReduceCombineDriver<IN, OUT> implements Driver<GroupCombineFunction<IN, OUT>, OUT> {
private static final Logger LOG = LoggerFactory.getLogger(GroupReduceCombineDriver.class);
/** Fix length records with a length below this threshold will be in-place sorted, if possible. */
private static final int THRESHOLD_FOR_IN_PLACE_SORTING = 32;
private TaskContext<GroupCombineFunction<IN, OUT>, OUT> taskContext;
private InMemorySorter<IN> sorter;
private GroupCombineFunction<IN, OUT> combiner;
private TypeSerializer<IN> serializer;
private TypeComparator<IN> groupingComparator;
private QuickSort sortAlgo = new QuickSort();
private Collector<OUT> output;
private List<MemorySegment> memory;
private long oversizedRecordCount;
private volatile boolean running = true;
private boolean objectReuseEnabled = false;
// ------------------------------------------------------------------------
@Override
public void setup(TaskContext<GroupCombineFunction<IN, OUT>, OUT> context) {
this.taskContext = context;
this.running = true;
}
@Override
public int getNumberOfInputs() {
return 1;
}
@Override
public Class<GroupCombineFunction<IN, OUT>> getStubType() {
@SuppressWarnings("unchecked")
final Class<GroupCombineFunction<IN, OUT>> clazz = (Class<GroupCombineFunction<IN, OUT>>) (Class<?>) GroupCombineFunction.class;
return clazz;
}
@Override
public int getNumberOfDriverComparators() {
return 2;
}
@Override
public void prepare() throws Exception {
final DriverStrategy driverStrategy = this.taskContext.getTaskConfig().getDriverStrategy();
if (driverStrategy != DriverStrategy.SORTED_GROUP_COMBINE){
throw new Exception("Invalid strategy " + driverStrategy + " for group reduce combiner.");
}
final TypeSerializerFactory<IN> serializerFactory = this.taskContext.getInputSerializer(0);
this.serializer = serializerFactory.getSerializer();
final TypeComparator<IN> sortingComparator = this.taskContext.getDriverComparator(0);
this.groupingComparator = this.taskContext.getDriverComparator(1);
this.combiner = this.taskContext.getStub();
this.output = this.taskContext.getOutputCollector();
MemoryManager memManager = this.taskContext.getMemoryManager();
final int numMemoryPages = memManager.computeNumberOfPages(this.taskContext.getTaskConfig().getRelativeMemoryDriver());
this.memory = memManager.allocatePages(this.taskContext.getContainingTask(), numMemoryPages);
// instantiate a fix-length in-place sorter, if possible, otherwise the out-of-place sorter
if (sortingComparator.supportsSerializationWithKeyNormalization() &&
this.serializer.getLength() > 0 && this.serializer.getLength() <= THRESHOLD_FOR_IN_PLACE_SORTING)
{
this.sorter = new FixedLengthRecordSorter<IN>(this.serializer, sortingComparator.duplicate(), memory);
} else {
this.sorter = new NormalizedKeySorter<IN>(this.serializer, sortingComparator.duplicate(), memory);
}
ExecutionConfig executionConfig = taskContext.getExecutionConfig();
this.objectReuseEnabled = executionConfig.isObjectReuseEnabled();
if (LOG.isDebugEnabled()) {
LOG.debug("GroupReduceCombineDriver object reuse: {}.", (this.objectReuseEnabled ? "ENABLED" : "DISABLED"));
}
}
@Override
public void run() throws Exception {
if (LOG.isDebugEnabled()) {
LOG.debug("Combiner starting.");
}
final MutableObjectIterator<IN> in = this.taskContext.getInput(0);
final TypeSerializer<IN> serializer = this.serializer;
if (objectReuseEnabled) {
IN value = serializer.createInstance();
while (running && (value = in.next(value)) != null) {
// try writing to the sorter first
if (this.sorter.write(value)) {
continue;
}
// do the actual sorting, combining, and data writing
sortAndCombineAndRetryWrite(value);
}
}
else {
IN value;
while (running && (value = in.next()) != null) {
// try writing to the sorter first
if (this.sorter.write(value)) {
continue;
}
// do the actual sorting, combining, and data writing
sortAndCombineAndRetryWrite(value);
}
}
// sort, combine, and send the final batch
if (running) {
sortAndCombine();
}
}
private void sortAndCombine() throws Exception {
if (sorter.isEmpty()) {
return;
}
final InMemorySorter<IN> sorter = this.sorter;
this.sortAlgo.sort(sorter);
final GroupCombineFunction<IN, OUT> combiner = this.combiner;
final Collector<OUT> output = this.output;
// iterate over key groups
if (objectReuseEnabled) {
final ReusingKeyGroupedIterator<IN> keyIter =
new ReusingKeyGroupedIterator<IN>(sorter.getIterator(), this.serializer, this.groupingComparator);
while (this.running && keyIter.nextKey()) {
combiner.combine(keyIter.getValues(), output);
}
} else {
final NonReusingKeyGroupedIterator<IN> keyIter =
new NonReusingKeyGroupedIterator<IN>(sorter.getIterator(), this.groupingComparator);
while (this.running && keyIter.nextKey()) {
combiner.combine(keyIter.getValues(), output);
}
}
}
private void sortAndCombineAndRetryWrite(IN value) throws Exception {
sortAndCombine();
this.sorter.reset();
// write the value again
if (!this.sorter.write(value)) {
++oversizedRecordCount;
LOG.debug("Cannot write record to fresh sort buffer, record is too large. " +
"Oversized record count: {}", oversizedRecordCount);
// simply forward the record. We need to pass it through the combine function to convert it
Iterable<IN> input = Collections.singleton(value);
this.combiner.combine(input, this.output);
this.sorter.reset();
}
}
@Override
public void cleanup() throws Exception {
if (this.sorter != null) {
this.sorter.dispose();
}
this.taskContext.getMemoryManager().release(this.memory);
}
@Override
public void cancel() {
this.running = false;
if (this.sorter != null) {
try {
this.sorter.dispose();
}
catch (Exception e) {
// may happen during concurrent modification
}
}
this.taskContext.getMemoryManager().release(this.memory);
}
/**
* Gets the number of oversized records handled by this combiner.
*
* @return The number of oversized records handled by this combiner.
*/
public long getOversizedRecordCount() {
return oversizedRecordCount;
}
}