DistributedVirtualDatabaseMessage


1   /**
2    * Sequoia: Database clustering technology.
3    * Copyright (C) 2006 Continuent, Inc.
4    * Contact: sequoia@continuent.org
5    * 
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * 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   * Initial developer(s): Emmanuel Cecchet.
19   * Contributor(s): ______________________.
20   */
21  
22  package org.continuent.sequoia.controller.virtualdatabase.protocol;
23  
24  import java.io.Serializable  ;
25  
26  import org.continuent.hedera.common.Member;
27  import org.continuent.sequoia.controller.virtualdatabase.DistributedVirtualDatabase;
28  
29  /**
30   * This interface defines a DistributedVirtualDatabaseMessage
31   * 
32   * @author <a HREF="mailto:emmanuel.cecchet@continuent.com">Emmanuel Cecchet</a>
33   * @version 1.0
34   */
35  public abstract class DistributedVirtualDatabaseMessage implements Serializable  
36  {
37  
38    /**
39     * Single threaded part of the handler that will execute in mutual execution
40     * in the total order delivery thread of the group communication.
41     * <p>
42     * NEVER BLOCK IN THIS HANDLER !!!
43     * 
44     * @param dvdb the local instance of the distributed virtual database
45     * @param sender the message sender
46     * @return an optional value to be passed to the multithreaded handler
47     */
48    public abstract Object   handleMessageSingleThreaded(
49        DistributedVirtualDatabase dvdb, Member sender);
50  
51    /**
52     * Multi-threaded part of the message handler.
53     * 
54     * @param dvdb the local instance of the distributed virtual database
55     * @param sender the message sender
56     * @param handleMessageSingleThreadedResult value returned by the single
57     *          threaded handler
58     * @return a Serializable object to be returned to the sender
59     */
60    public abstract Serializable   handleMessageMultiThreaded(
61        DistributedVirtualDatabase dvdb, Member sender,
62        Object   handleMessageSingleThreadedResult);
63  
64    /**
65     * Cancel the message in a "best effort"-basis. Should try to undo message
66     * side-effects and clean-up reources.
67     * 
68     * @param dvdb the local instance of the distributed virtual database
69     */
70    public void cancel(DistributedVirtualDatabase dvdb)
71    {
72      // Does nothing by default.
73    }
74  }
75
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