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Server functionality for HBase
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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.hadoop.hbase.regionserver;

import java.io.IOException;
import java.util.List;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.monitoring.MonitoredTask;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * A package protected interface for a store flushing. A store flush context carries the state
 * required to prepare/flush/commit the store's cache.
 */
@InterfaceAudience.Private
interface StoreFlushContext {

  /**
   * Prepare for a store flush (create snapshot) Requires pausing writes. A very short operation.
   * @return The size of snapshot to flush
   */
  MemStoreSize prepare();

  /**
   * Flush the cache (create the new store file) A length operation which doesn't require locking
   * out any function of the store.
   * @throws IOException in case the flush fails
   */
  void flushCache(MonitoredTask status) throws IOException;

  /**
   * Commit the flush - add the store file to the store and clear the memstore snapshot. Requires
   * pausing scans. A very short operation
   * @return whether compaction is required
   */
  boolean commit(MonitoredTask status) throws IOException;

  /**
   * Similar to commit, but called in secondary region replicas for replaying the flush cache from
   * primary region. Adds the new files to the store, and drops the snapshot depending on
   * dropMemstoreSnapshot argument.
   * @param fileNames            names of the flushed files
   * @param dropMemstoreSnapshot whether to drop the prepared memstore snapshot
   */
  void replayFlush(List fileNames, boolean dropMemstoreSnapshot) throws IOException;

  /**
   * Abort the snapshot preparation. Drops the snapshot if any.
   */
  void abort() throws IOException;

  /**
   * Returns the newly committed files from the flush. Called only if commit returns true
   * @return a list of Paths for new files
   */
  List getCommittedFiles();

  /** Returns the total file size for flush output files, in bytes */
  long getOutputFileSize();
}