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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.samza.translation;
  
  import com.google.auto.service.AutoService;
  import org.apache.beam.model.pipeline.v1.RunnerApi;
  import org.apache.beam.runners.samza.runtime.OpMessage;
  import org.apache.beam.runners.samza.util.SamzaCoders;
  import org.apache.beam.runners.samza.util.WindowUtils;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.coders.KvCoder;
  import org.apache.beam.sdk.runners.TransformHierarchy;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.util.construction.NativeTransforms;
  import org.apache.beam.sdk.util.construction.graph.PipelineNode;
  import org.apache.beam.sdk.util.construction.graph.QueryablePipeline;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.beam.sdk.values.WindowedValues;
  import org.apache.samza.operators.MessageStream;
  import org.apache.samza.serializers.KVSerde;
  
  /**
   * Translates Reshuffle transform into Samza's native partitionBy operator, which will partition
   * each incoming message by the key into a Task corresponding to that key.
   */
  public class ReshuffleTranslator<K, InT, OutT>
      implements TransformTranslator<PTransform<PCollection<KV<K, InT>>, PCollection<KV<K, OutT>>>> {
  
    private final String prefix;
  
    ReshuffleTranslator(String prefix) {
      this.prefix = prefix;
    }
  
    ReshuffleTranslator() {
      this("rshfl-");
    }
  
    @Override
    public void translate(
        PTransform<PCollection<KV<K, InT>>, PCollection<KV<K, OutT>>> transform,
        TransformHierarchy.Node node,
        TranslationContext ctx) {
  
      final PCollection<KV<K, InT>> input = ctx.getInput(transform);
      final PCollection<KV<K, OutT>> output = ctx.getOutput(transform);
      final MessageStream<OpMessage<KV<K, InT>>> inputStream = ctx.getMessageStream(input);
      // input will be OpMessage of Windowed<KV<K, Iterable<V>>>
      final KvCoder<K, InT> inputCoder = (KvCoder<K, InT>) input.getCoder();
      final Coder<WindowedValue<KV<K, InT>>> elementCoder = SamzaCoders.of(input);
  
      final MessageStream<OpMessage<KV<K, InT>>> outputStream =
          doTranslate(
              inputStream,
              inputCoder.getKeyCoder(),
              elementCoder,
              prefix + ctx.getTransformId(),
              ctx.getPipelineOptions().getMaxSourceParallelism() > 1);
  
      ctx.registerMessageStream(output, outputStream);
    }
  
    @Override
    public void translatePortable(
        PipelineNode.PTransformNode transform,
        QueryablePipeline pipeline,
        PortableTranslationContext ctx) {
  
      final String inputId = ctx.getInputId(transform);
      final MessageStream<OpMessage<KV<K, InT>>> inputStream = ctx.getMessageStreamById(inputId);
      final WindowedValues.WindowedValueCoder<KV<K, InT>> windowedInputCoder =
          WindowUtils.instantiateWindowedCoder(inputId, pipeline.getComponents());
      final String outputId = ctx.getOutputId(transform);
  
      final MessageStream<OpMessage<KV<K, InT>>> outputStream =
          doTranslate(
              inputStream,
              ((KvCoder<K, InT>) windowedInputCoder.getValueCoder()).getKeyCoder(),
              windowedInputCoder,
              prefix + ctx.getTransformId(),
              ctx.getPipelineOptions().getMaxSourceParallelism() > 1);
  
      ctx.registerMessageStream(outputId, outputStream);
    }
  
    private static <K, InT> MessageStream<OpMessage<KV<K, InT>>> doTranslate(
        MessageStream<OpMessage<KV<K, InT>>> inputStream,
        Coder<K> keyCoder,
        Coder<WindowedValue<KV<K, InT>>> valueCoder,
        String partitionById, // will be used in the intermediate stream name
        boolean needRepartition) {
  
      return needRepartition
          ? inputStream
              .filter(op -> OpMessage.Type.ELEMENT == op.getType())
              .partitionBy(
                  opMessage -> opMessage.getElement().getValue().getKey(),
                  OpMessage::getElement, // windowed value
                  KVSerde.of(SamzaCoders.toSerde(keyCoder), SamzaCoders.toSerde(valueCoder)),
                  partitionById)
              // convert back to OpMessage
              .map(kv -> OpMessage.ofElement(kv.getValue()))
          : inputStream.filter(op -> OpMessage.Type.ELEMENT == op.getType());
    }
  
    /** Predicate to determine whether a URN is a Samza native transform. */
    @AutoService(NativeTransforms.IsNativeTransform.class)
    public static class IsSamzaNativeTransform implements NativeTransforms.IsNativeTransform {
      @Override
      public boolean test(RunnerApi.PTransform pTransform) {
        return false;
        // Re-enable after https://github.com/apache/beam/issues/21188 is completed
        //       return PTransformTranslation.RESHUFFLE_URN.equals(
        //          PTransformTranslation.urnForTransformOrNull(pTransform));
      }
    }
  }
  