runners/flink/src/main/java/org/apache/beam/runners/flink/translation/wrappers/streaming/state/KeyGroupCheckpointedOperator.java

/*
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 * distributed with this work for additional information
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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
 *
 * Unless required by applicable law or agreed to in writing, software
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package org.apache.beam.runners.flink.translation.wrappers.streaming.state;

import java.io.DataOutputStream;

/** This interface is used to checkpoint key-groups state. */
public interface KeyGroupCheckpointedOperator extends KeyGroupRestoringOperator {
  /**
   * Snapshots the state for a given {@code keyGroupIdx}.
   *
   * <p>AbstractStreamOperator would call this hook in AbstractStreamOperator.snapshotState() while
   * iterating over the key groups.
   *
   * @param keyGroupIndex the id of the key-group to be put in the snapshot.
   * @param out the stream to write to.
   */
  void snapshotKeyGroupState(int keyGroupIndex, DataOutputStream out) throws Exception;
}