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[BEAM-5392] GroupByKey optimized for non-merging windows
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242
.../main/java/org/apache/beam/runners/spark/translation/GroupNonMergingWindowsFunctions.java
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/* | ||
* 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.beam.runners.spark.translation; | ||
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import java.io.Serializable; | ||
import java.util.Arrays; | ||
import java.util.Iterator; | ||
import java.util.Objects; | ||
import org.apache.beam.runners.spark.coders.CoderHelpers; | ||
import org.apache.beam.sdk.coders.ByteArrayCoder; | ||
import org.apache.beam.sdk.coders.Coder; | ||
import org.apache.beam.sdk.transforms.windowing.BoundedWindow; | ||
import org.apache.beam.sdk.util.WindowedValue; | ||
import org.apache.beam.sdk.util.WindowedValue.FullWindowedValueCoder; | ||
import org.apache.beam.sdk.values.KV; | ||
import org.apache.beam.sdk.values.WindowingStrategy; | ||
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.AbstractIterator; | ||
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Iterables; | ||
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Iterators; | ||
import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.PeekingIterator; | ||
import org.apache.beam.vendor.guava.v20_0.com.google.common.primitives.UnsignedBytes; | ||
import org.apache.spark.HashPartitioner; | ||
import org.apache.spark.api.java.JavaRDD; | ||
import org.joda.time.Instant; | ||
import scala.Tuple2; | ||
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/** Functions for GroupByKey with Non-Merging windows translations to Spark. */ | ||
public class GroupNonMergingWindowsFunctions { | ||
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static <K, V, W extends BoundedWindow> | ||
JavaRDD<WindowedValue<KV<K, Iterable<V>>>> groupByKeyAndWindow( | ||
JavaRDD<WindowedValue<KV<K, V>>> rdd, | ||
Coder<K> keyCoder, | ||
Coder<V> valueCoder, | ||
WindowingStrategy<?, W> windowingStrategy) { | ||
final Coder<W> windowCoder = windowingStrategy.getWindowFn().windowCoder(); | ||
final WindowedValue.FullWindowedValueCoder<byte[]> windowedValueCoder = | ||
WindowedValue.getFullCoder(ByteArrayCoder.of(), windowCoder); | ||
return rdd.flatMapToPair( | ||
(WindowedValue<KV<K, V>> windowedValue) -> { | ||
final byte[] keyBytes = | ||
CoderHelpers.toByteArray(windowedValue.getValue().getKey(), keyCoder); | ||
final byte[] valueBytes = | ||
CoderHelpers.toByteArray(windowedValue.getValue().getValue(), valueCoder); | ||
return Iterators.transform( | ||
windowedValue.explodeWindows().iterator(), | ||
item -> { | ||
Objects.requireNonNull(item, "Exploded window can not be null."); | ||
@SuppressWarnings("unchecked") | ||
final W window = (W) Iterables.getOnlyElement(item.getWindows()); | ||
final byte[] windowBytes = CoderHelpers.toByteArray(window, windowCoder); | ||
final byte[] windowValueBytes = | ||
CoderHelpers.toByteArray( | ||
WindowedValue.of( | ||
valueBytes, item.getTimestamp(), window, item.getPane()), | ||
windowedValueCoder); | ||
final WindowedKey windowedKey = new WindowedKey(keyBytes, windowBytes); | ||
return new Tuple2<>(windowedKey, windowValueBytes); | ||
}); | ||
}) | ||
.repartitionAndSortWithinPartitions(new HashPartitioner(rdd.getNumPartitions())) | ||
.mapPartitions( | ||
it -> | ||
new GroupByKeyIterator<>( | ||
it, keyCoder, valueCoder, windowingStrategy, windowedValueCoder)) | ||
.filter(Objects::nonNull); // filter last null element from GroupByKeyIterator | ||
} | ||
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/** | ||
* Transform stream of sorted key values into stream of value iterators for each key. This | ||
* iterator can be iterated only once! | ||
* | ||
* @param <K> type of key iterator emits | ||
* @param <V> type of value iterator emits | ||
*/ | ||
static class GroupByKeyIterator<K, V, W extends BoundedWindow> | ||
implements Iterator<WindowedValue<KV<K, Iterable<V>>>> { | ||
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private final PeekingIterator<Tuple2<WindowedKey, byte[]>> inner; | ||
private final Coder<K> keyCoder; | ||
private final Coder<V> valueCoder; | ||
private final WindowingStrategy<?, W> windowingStrategy; | ||
private final FullWindowedValueCoder<byte[]> windowedValueCoder; | ||
private boolean hasNext = true; | ||
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private WindowedKey currentKey = null; | ||
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GroupByKeyIterator( | ||
Iterator<Tuple2<WindowedKey, byte[]>> inner, | ||
Coder<K> keyCoder, | ||
Coder<V> valueCoder, | ||
WindowingStrategy<?, W> windowingStrategy, | ||
WindowedValue.FullWindowedValueCoder<byte[]> windowedValueCoder) { | ||
this.inner = Iterators.peekingIterator(inner); | ||
this.keyCoder = keyCoder; | ||
this.valueCoder = valueCoder; | ||
this.windowingStrategy = windowingStrategy; | ||
this.windowedValueCoder = windowedValueCoder; | ||
} | ||
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@Override | ||
public boolean hasNext() { | ||
return hasNext; | ||
} | ||
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@Override | ||
public WindowedValue<KV<K, Iterable<V>>> next() { | ||
while (inner.hasNext()) { | ||
final WindowedKey nextKey = inner.peek()._1; | ||
if (nextKey.equals(currentKey)) { | ||
// we still did not see all values for a given key | ||
inner.next(); | ||
continue; | ||
} | ||
currentKey = nextKey; | ||
final WindowedValue<KV<K, V>> decodedItem = decodeItem(inner.peek()); | ||
return decodedItem.withValue( | ||
KV.of(decodedItem.getValue().getKey(), new ValueIterator(inner, currentKey))); | ||
} | ||
hasNext = false; | ||
return null; | ||
} | ||
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class ValueIterator implements Iterable<V> { | ||
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boolean usedAsIterable = false; | ||
private final PeekingIterator<Tuple2<WindowedKey, byte[]>> inner; | ||
private WindowedKey currentKey; | ||
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ValueIterator(PeekingIterator<Tuple2<WindowedKey, byte[]>> inner, WindowedKey currentKey) { | ||
this.inner = inner; | ||
this.currentKey = currentKey; | ||
} | ||
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@Override | ||
public Iterator<V> iterator() { | ||
if (usedAsIterable) { | ||
throw new IllegalStateException( | ||
"ValueIterator can't be iterated more than once," | ||
+ "otherwise there could be data lost"); | ||
} | ||
usedAsIterable = true; | ||
return new AbstractIterator<V>() { | ||
@Override | ||
protected V computeNext() { | ||
if (inner.hasNext() && currentKey.equals(inner.peek()._1)) { | ||
return decodeValue(inner.next()._2); | ||
} | ||
return endOfData(); | ||
} | ||
}; | ||
} | ||
} | ||
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private V decodeValue(byte[] windowedValueBytes) { | ||
final WindowedValue<byte[]> windowedValue = | ||
CoderHelpers.fromByteArray(windowedValueBytes, windowedValueCoder); | ||
return CoderHelpers.fromByteArray(windowedValue.getValue(), valueCoder); | ||
} | ||
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private WindowedValue<KV<K, V>> decodeItem(Tuple2<WindowedKey, byte[]> item) { | ||
final K key = CoderHelpers.fromByteArray(item._1.getKey(), keyCoder); | ||
final WindowedValue<byte[]> windowedValue = | ||
CoderHelpers.fromByteArray(item._2, windowedValueCoder); | ||
final V value = CoderHelpers.fromByteArray(windowedValue.getValue(), valueCoder); | ||
@SuppressWarnings("unchecked") | ||
final W window = (W) Iterables.getOnlyElement(windowedValue.getWindows()); | ||
final Instant timestamp = | ||
windowingStrategy | ||
.getTimestampCombiner() | ||
.assign( | ||
window, | ||
windowingStrategy | ||
.getWindowFn() | ||
.getOutputTime(windowedValue.getTimestamp(), window)); | ||
return WindowedValue.of(KV.of(key, value), timestamp, window, windowedValue.getPane()); | ||
} | ||
} | ||
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/** Composite key of key and window for groupByKey transformation. */ | ||
public static class WindowedKey implements Comparable<WindowedKey>, Serializable { | ||
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private final byte[] key; | ||
private final byte[] window; | ||
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WindowedKey(byte[] key, byte[] window) { | ||
this.key = key; | ||
this.window = window; | ||
} | ||
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@Override | ||
public boolean equals(Object o) { | ||
if (this == o) { | ||
return true; | ||
} | ||
if (o == null || getClass() != o.getClass()) { | ||
return false; | ||
} | ||
WindowedKey that = (WindowedKey) o; | ||
return Arrays.equals(key, that.key) && Arrays.equals(window, that.window); | ||
} | ||
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@Override | ||
public int hashCode() { | ||
int result = Arrays.hashCode(key); | ||
result = 31 * result + Arrays.hashCode(window); | ||
return result; | ||
} | ||
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public byte[] getKey() { | ||
return key; | ||
} | ||
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public byte[] getWindow() { | ||
return window; | ||
} | ||
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@Override | ||
public int compareTo(WindowedKey o) { | ||
int keyCompare = UnsignedBytes.lexicographicalComparator().compare(this.getKey(), o.getKey()); | ||
if (keyCompare == 0) { | ||
return UnsignedBytes.lexicographicalComparator().compare(this.getWindow(), o.getWindow()); | ||
} | ||
return keyCompare; | ||
} | ||
} | ||
} |
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