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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.hbase.regionserver;
20  
21  import java.io.IOException;
22  
23  import org.apache.hadoop.classification.InterfaceAudience;
24  import org.apache.hadoop.hbase.monitoring.MonitoredTask;
25  
26  /**
27   * A package protected interface for a store flushing.
28   * A store flusher carries the state required to prepare/flush/commit the
29   * store's cache.
30   */
31  @InterfaceAudience.Private
32  interface StoreFlusher {
33  
34    /**
35     * Prepare for a store flush (create snapshot)
36     *
37     * Requires pausing writes.
38     *
39     * A very short operation.
40     */
41    void prepare();
42  
43    /**
44     * Flush the cache (create the new store file)
45     *
46     * A length operation which doesn't require locking out any function
47     * of the store.
48     *
49     * @throws IOException in case the flush fails
50     */
51    void flushCache(MonitoredTask status) throws IOException;
52  
53    /**
54     * Commit the flush - add the store file to the store and clear the
55     * memstore snapshot.
56     *
57     * Requires pausing scans.
58     *
59     * A very short operation
60     *
61     * @return
62     * @throws IOException
63     */
64    boolean commit(MonitoredTask status) throws IOException;
65  }