samza-api/src/main/java/org/apache/samza/container/grouper/stream/SystemStreamPartitionMapper.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
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 */
package org.apache.samza.container.grouper.stream;

import org.apache.samza.system.SystemStreamPartition;

/**
 * Input streams of a samza job can be either expanded or contracted by the user.
 * This abstraction determines the previous {@link SystemStreamPartition} for a {@link SystemStreamPartition}
 * of a input stream after the stream expansion or contraction.
 */
public interface SystemStreamPartitionMapper {

  /**
   * Determines the previous {@link SystemStreamPartition} for a {@link SystemStreamPartition}
   * of a input stream after the stream expansion or contraction.
   * @param currentSystemStreamPartition denotes the current partition after the stream partition count change.
   * @param previousPartitionCount the partition count of the stream before the stream partition count change.
   * @param currentPartitionCount the partition count of the stream after the stream partition count change.
   * @return the mapped {@link SystemStreamPartition}.
   */
  SystemStreamPartition getPreviousSSP(SystemStreamPartition currentSystemStreamPartition,
                                       int previousPartitionCount, int currentPartitionCount);
}