org.apache.flink.runtime.checkpoint.OperatorStateRepartitioner Maven / Gradle / Ivy

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
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 * 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,
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 * See the License for the specific language governing permissions and
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 */

package org.apache.flink.runtime.checkpoint;

import org.apache.flink.annotation.Internal;

import java.util.List;

/**
 * Interface that allows to implement different strategies for repartitioning of operator state as
 * parallelism changes.
 */
@Internal
public interface OperatorStateRepartitioner {

    /**
     * @param previousParallelSubtaskStates List with one entry of state handles per parallel
     *     subtask of an operator, as they have been checkpointed.
     * @param oldParallelism The parallelism before we start redistribution.
     * @param newParallelism The parallelism that we consider for the state redistribution.
     *     Determines the size of the returned list.
     * @return List with one entry per parallel subtask. Each subtask receives now one collection of
     *     states that build of the new total state for this subtask.
     */
    List> repartitionState(
            List> previousParallelSubtaskStates, int oldParallelism, int newParallelism);
}