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* Licensed to the Apache Software Foundation (ASF) under one
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* 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.sdk.transforms;
import org.apache.beam.sdk.annotations.Internal;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.transforms.windowing.ReshuffleTrigger;
import org.apache.beam.sdk.transforms.windowing.TimestampCombiner;
import org.apache.beam.sdk.transforms.windowing.Window;
import org.apache.beam.sdk.util.IdentityWindowFn;
import org.apache.beam.sdk.values.KV;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.TimestampedValue;
import org.apache.beam.sdk.values.WindowingStrategy;
import org.joda.time.Duration;
/**
* <b>For internal use only; no backwards compatibility guarantees.</b>
*
* <p>A {@link PTransform} that returns a {@link PCollection} equivalent to its input but
* operationally provides some of the side effects of a {@link GroupByKey}, in particular preventing
* fusion of the surrounding transforms, checkpointing and deduplication by id.
*
* <p>Performs a {@link GroupByKey} so that the data is key-partitioned. Configures the {@link
* WindowingStrategy} so that no data is dropped, but doesn't affect the need for the user to
* specify allowed lateness and accumulation mode before a user-inserted GroupByKey.
*
* @param <K> The type of key being reshuffled on.
* @param <V> The type of value being reshuffled.
* @deprecated this transform's intended side effects are not portable; it will likely be removed
*/
@Internal
@Deprecated
public class Reshuffle<K, V> extends PTransform<PCollection<KV<K, V>>, PCollection<KV<K, V>>> {
private Reshuffle() {
}
public static <K, V> Reshuffle<K, V> of() {
return new Reshuffle<K, V>();
}
@Override
public PCollection<KV<K, V>> expand(PCollection<KV<K, V>> input) {
WindowingStrategy<?, ?> originalStrategy = input.getWindowingStrategy();
// If the input has already had its windows merged, then the GBK that performed the merge
// will have set originalStrategy.getWindowFn() to InvalidWindows, causing the GBK contained
// here to fail. Instead, we install a valid WindowFn that leaves all windows unchanged.
// The TimestampCombiner is set to ensure the GroupByKey does not shift elements forwards in
// time.
// Because this outputs as fast as possible, this should not hold the watermark.
Window<KV<K, V>> rewindow =
Window.<KV<K, V>>into(new IdentityWindowFn<>(originalStrategy.getWindowFn().windowCoder()))
.triggering(new ReshuffleTrigger<>())
.discardingFiredPanes()
.withTimestampCombiner(TimestampCombiner.EARLIEST)
.withAllowedLateness(Duration.millis(BoundedWindow.TIMESTAMP_MAX_VALUE.getMillis()));
return input
.apply(rewindow)
.apply("ReifyOriginalTimestamps", ReifyTimestamps.<K, V>inValues())
.apply(GroupByKey.<K, TimestampedValue<V>>create())
// Set the windowing strategy directly, so that it doesn't get counted as the user having
// set allowed lateness.
.setWindowingStrategyInternal(originalStrategy)
.apply(
"ExpandIterable",
ParDo.of(
new DoFn<KV<K, Iterable<TimestampedValue<V>>>, KV<K, TimestampedValue<V>>>() {
@ProcessElement
public void processElement(ProcessContext c) {
K key = c.element().getKey();
for (TimestampedValue<V> value : c.element().getValue()) {
c.output(KV.of(key, value));
}
}
}))
.apply(
"RestoreOriginalTimestamps",
ReifyTimestamps.<K, V>extractFromValues());
}
}