heron/api/src/java/org/apache/heron/streamlet/impl/streamlets/RemapStreamlet.java

/**
 * 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.heron.streamlet.impl.streamlets;

import java.util.List;
import java.util.Set;

import org.apache.heron.api.topology.TopologyBuilder;
import org.apache.heron.streamlet.SerializableBiFunction;
import org.apache.heron.streamlet.impl.StreamletImpl;
import org.apache.heron.streamlet.impl.groupings.RemapCustomGrouping;
import org.apache.heron.streamlet.impl.operators.MapOperator;

/**
 * RemapStreamlet represents a Streamlet that is the result of
 * applying user supplied remapFn on all elements of its parent Streamlet.
 * RemapStreamlet as such is a generalized version of the Map/FlatMapStreamlets
 * that give users more flexibility over the operation. The remapFn allows for
 * users to choose which destination shards every transformed element can go.
 */
public class RemapStreamlet<R> extends StreamletImpl<R> {
  private StreamletImpl<R> parent;
  private SerializableBiFunction<? super R, Integer, List<Integer>> remapFn;

  public RemapStreamlet(StreamletImpl<R> parent,
                        SerializableBiFunction<? super R, Integer, List<Integer>> remapFn) {
    this.parent = parent;
    this.remapFn = remapFn;
    setNumPartitions(parent.getNumPartitions());
  }

  @Override
  public boolean doBuild(TopologyBuilder bldr, Set<String> stageNames) {
    setDefaultNameIfNone(StreamletNamePrefix.REMAP, stageNames);
    bldr.setBolt(getName(), new MapOperator<R, R>((a) -> a), getNumPartitions())
        .customGrouping(parent.getName(), parent.getStreamId(),
            new RemapCustomGrouping<R>(remapFn));
    return true;
  }
}