org.apache.beam.runners.dataflow.ReshuffleOverrideFactory Maven / Gradle / Ivy

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 * 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
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 * Unless required by applicable law or agreed to in writing, software
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 * See the License for the specific language governing permissions and
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package org.apache.beam.runners.dataflow;

import org.apache.beam.runners.core.construction.PTransformReplacements;
import org.apache.beam.runners.core.construction.SingleInputOutputOverrideFactory;
import org.apache.beam.sdk.runners.AppliedPTransform;
import org.apache.beam.sdk.runners.PTransformOverrideFactory;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.GroupByKey;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.transforms.Reshuffle;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.transforms.windowing.ReshuffleTrigger;
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.WindowingStrategy;
import org.joda.time.Duration;

/**
 * A {@link PTransformOverrideFactory} that overrides {@link Reshuffle} with a version that does not
 * reify timestamps. Dataflow has special handling of the {@link ReshuffleTrigger} which never
 * buffers elements and outputs elements with their original timestamp.
 */
class ReshuffleOverrideFactory
    extends SingleInputOutputOverrideFactory<
        PCollection>, PCollection>, Reshuffle> {
  @Override
  public PTransformReplacement>, PCollection>>
      getReplacementTransform(
          AppliedPTransform>, PCollection>, Reshuffle>
              transform) {
    return PTransformReplacement.of(
        PTransformReplacements.getSingletonMainInput(transform),
        new ReshuffleWithOnlyTrigger());
  }

  private static class ReshuffleWithOnlyTrigger
      extends PTransform>, PCollection>> {
    @Override
    public PCollection> expand(PCollection> 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.
      Window> rewindow =
          Window.>into(
              new IdentityWindowFn<>(
                  originalStrategy.getWindowFn().windowCoder()))
              .triggering(new ReshuffleTrigger<>())
              .discardingFiredPanes()
              .withAllowedLateness(Duration.millis(BoundedWindow.TIMESTAMP_MAX_VALUE.getMillis()));

      return input.apply(rewindow)
          .apply(GroupByKey.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>() {
                @ProcessElement
                public void processElement(ProcessContext c) {
                  K key = c.element().getKey();
                  for (V value : c.element().getValue()) {
                    c.output(KV.of(key, value));
                  }
                }
              }));
    }
  }
}