AopLRUPolicy


1   /*
2    * JBoss, the OpenSource J2EE webOS
3    *
4    * Distributable under LGPL license.
5    * See terms of license at gnu.org.
6    * Created on March 25 2003
7    */
8   package org.jboss.cache.eviction;
9   import org.jboss.cache.Fqn;
10  import org.jboss.cache.aop.AOPInstance;
11  import org.jboss.cache.aop.TreeCacheAop;
12  
13  import java.util.Iterator  ;
14  import java.util.Set  ;
15  
16  
17  /** Provider to provide eviction policy. This one is based on LRU algorithm that a user
18   * can specify either maximum number of nodes or the idle time of a node to be evicted.
19   *
20   * @author Ben Wang 02-2004
21   */
22  public class AopLRUPolicy extends LRUPolicy  implements AopEvictionPolicy
23  {
24     public AopLRUPolicy() {
25        super();
26     }
27  
28     /**
29      * Override for aop-specific. In this case, if a node is visited and it is an aop-node, i.e.,
30      * it has AopInstance, then all the children nodes are considered visited as well.
31      * @param fqn
32      */
33     public void nodeVisited(Fqn fqn)
34     {
35        if(isInternalNode(fqn)) return;
36  
37        Region region = regionManager_.getRegion(fqn.toString());
38        // TODO May need to optimize to check if this fqn is already on the queue. No need to process it twice.
39        region.setVisitedNode(fqn);
40  
41        if(!isAopNode(fqn))
42           return;
43  
44  
45        visitChildrenRecursively(region, fqn);
46     }
47  
48     protected void visitChildrenRecursively(Region region, Fqn fqn) {
49        Set   set = getChildrenNames(fqn);
50        int size = (set == null) ? 0: set.size();
51        if(log_.isTraceEnabled()) {
52           log_.trace("nodeVisited(): is an aop node. fqn- " +fqn + " size of children is " +size);
53        }
54  
55        if(set == null) return; // barren
56        Iterator   it = set.iterator();
57        while(it.hasNext()) {
58           Object   childName = it.next();
59           Fqn fqnKid = new Fqn(fqn, childName);
60           visitChildrenRecursively(region, fqnKid);
61           region.setVisitedNode(fqnKid);
62        }
63     }
64  
65     private boolean isAopNode(Fqn fqn)
66     {
67        try {
68           return (cache_.peek(fqn, AOPInstance.KEY) != null) ? true: false;
69        } catch (Exception   e) {
70           log_.warn("isAopNode(): cache get operation generated exception " +e);
71           return false;
72        }
73     }
74  
75     public void nodeAdded(Fqn fqn)
76     {
77        if(isInternalNode(fqn)) return;
78  
79        super.nodeAdded(fqn);
80     }
81  
82     /**
83      * Note that this removes all children nodes as well. So we will need to put the children nodes
84      * into removed queue.
85      * @param fqn
86      */
87     public void nodeRemoved(Fqn fqn)
88     {
89        if(isInternalNode(fqn)) return;
90  
91        super.nodeRemoved(fqn);
92     }
93  
94     public void nodeModified(Fqn fqn) {
95        super.nodeModified(fqn);
96     }
97  
98     // we are using the same eviction algorithm now.
99     protected EvictionAlgorithm getEvictionAlgorithm() {
100       return new LRUAlgorithm();
101    }
102 
103    /**
104     * Check if this is an JBossInternal node. If it is, no need to proceed since we don't
105     * care about it.
106     * @param fqn
107     * @return
108     */
109    protected boolean isInternalNode(Fqn fqn) {
110       String   startStr = (String  )fqn.get(0);
111       if( startStr.equals(TreeCacheAop.JBOSS_INTERNAL.get(0))) return true;
112 
113       return false;
114    }
115 }
116
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