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1   /*
2    *
3    * Licensed under the Apache License, Version 2.0 (the "License");
4    * you may not use this file except in compliance with the License.
5    * You may obtain a copy of the License at
6    *
7    *     http://www.apache.org/licenses/LICENSE-2.0
8    *
9    * Unless required by applicable law or agreed to in writing, software
10   * distributed under the License is distributed on an "AS IS" BASIS,
11   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12   * See the License for the specific language governing permissions and
13   * limitations under the License.
14   */
15  
16  package org.apache.hadoop.hbase;
17  
18  import org.apache.hadoop.classification.InterfaceAudience;
19  import org.apache.hadoop.classification.InterfaceStability;
20  
21  import java.io.IOException;
22  
23  /**
24   * Coprocess interface.
25   */
26  @InterfaceAudience.Public
27  @InterfaceStability.Evolving
28  public interface Coprocessor {
29    int VERSION = 1;
30  
31    /** Highest installation priority */
32    int PRIORITY_HIGHEST = 0;
33    /** High (system) installation priority */
34    int PRIORITY_SYSTEM = Integer.MAX_VALUE / 4;
35    /** Default installation priority for user coprocessors */
36    int PRIORITY_USER = Integer.MAX_VALUE / 2;
37    /** Lowest installation priority */
38    int PRIORITY_LOWEST = Integer.MAX_VALUE;
39  
40    /**
41     * Lifecycle state of a given coprocessor instance.
42     */
43    enum State {
44      UNINSTALLED,
45      INSTALLED,
46      STARTING,
47      ACTIVE,
48      STOPPING,
49      STOPPED
50    }
51  
52    // Interface
53    void start(CoprocessorEnvironment env) throws IOException;
54  
55    void stop(CoprocessorEnvironment env) throws IOException;
56  }