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1   package org.apache.jcs.auxiliary.disk.jdbc;
2   
3   /*
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *   http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  
22  import java.util.Collections;
23  import java.util.HashSet;
24  import java.util.Set;
25  
26  import org.apache.commons.logging.Log;
27  import org.apache.commons.logging.LogFactory;
28  
29  /***
30   * Calls delete expired on the disk caches. The shrinker is run by a clock daemon. The shrinker
31   * calls delete on each region. It pauses between calls.
32   * <p>
33   * @author Aaron Smuts
34   */
35  public class ShrinkerThread
36      implements Runnable
37  {
38      /*** The logger. */
39      private final static Log log = LogFactory.getLog( ShrinkerThread.class );
40  
41      /*** A set of JDBCDiskCache objects to call deleteExpired on. */
42      private Set shrinkSet = Collections.synchronizedSet( new HashSet() );
43  
44      /***
45       * Default time period to use.
46       */
47      private static final long DEFAULT_PAUSE_BETWEEN_REGION_CALLS_MILLIS = 5000;
48  
49      /***
50       * How long should we wait between calls to deleteExpired when we are iterating through the list
51       * of regions. Delete can lock the table. We want to give clients a chance to get some work
52       * done.
53       */
54      private long pauseBetweenRegionCallsMillis = DEFAULT_PAUSE_BETWEEN_REGION_CALLS_MILLIS;
55  
56      /***
57       * Does nothing special.
58       * <p>
59       * @param diskCache
60       */
61      protected ShrinkerThread()
62      {
63          super();
64      }
65  
66      /***
67       * Adds a JDBC disk cache to the set of disk cache to shrink.
68       * <p>
69       * @param diskCache
70       */
71      public void addDiskCacheToShrinkList( JDBCDiskCache diskCache )
72      {
73          // the set will prevent dupes.
74          // we could also just add these to a hasmap by region name
75          // but that might cause a problem if you wanted to use two different
76          // jbdc disk caches for the same region.
77          shrinkSet.add( diskCache );
78      }
79  
80      /***
81       * Calls deleteExpired on each item in the set. It pauses between each call.
82       */
83      public void run()
84      {
85          if ( log.isInfoEnabled() )
86          {
87              log.info( "Running JDBC disk cache shrinker.  Number of regions [" + shrinkSet.size() + "]" );
88          }
89  
90          Object[] caches = null;
91  
92          synchronized ( shrinkSet )
93          {
94              caches = this.shrinkSet.toArray();
95          }
96  
97          if ( caches != null )
98          {
99              for ( int i = 0; i < caches.length; i++ )
100             {
101                 JDBCDiskCache cache = (JDBCDiskCache) caches[i];
102 
103                 long start = System.currentTimeMillis();
104                 int deleted = cache.deleteExpired();
105                 long end = System.currentTimeMillis();
106 
107                 if ( log.isInfoEnabled() )
108                 {
109                     log.info( "Deleted [" + deleted + "] expired for region [" + cache.getCacheName() + "] for table ["
110                         + cache.getTableName() + "] in " + ( end - start ) + " ms." );
111                 }
112 
113                 // don't pause after the last call to delete expired.
114                 if ( i < caches.length - 1 )
115                 {
116                     if ( log.isInfoEnabled() )
117                     {
118                         log.info( "Pausing for [" + this.getPauseBetweenRegionCallsMillis()
119                             + "] ms. before shinker the next region." );
120                     }
121 
122                     try
123                     {
124                         Thread.sleep( this.getPauseBetweenRegionCallsMillis() );
125                     }
126                     catch ( InterruptedException e )
127                     {
128                         log.warn( "Interrupted while waiting to delete expired for the enxt region." );
129                     }
130                 }
131             }
132         }
133     }
134 
135     /***
136      * How long should we wait between calls to deleteExpired when we are iterating through the list
137      * of regions.
138      * <p>
139      * @param pauseBetweenRegionCallsMillis The pauseBetweenRegionCallsMillis to set.
140      */
141     public void setPauseBetweenRegionCallsMillis( long pauseBetweenRegionCallsMillis )
142     {
143         this.pauseBetweenRegionCallsMillis = pauseBetweenRegionCallsMillis;
144     }
145 
146     /***
147      * How long should we wait between calls to deleteExpired when we are iterating through the list
148      * of regions.
149      * <p>
150      * @return Returns the pauseBetweenRegionCallsMillis.
151      */
152     public long getPauseBetweenRegionCallsMillis()
153     {
154         return pauseBetweenRegionCallsMillis;
155     }
156 }