[jboss-user] [JBoss Cache] New message: "How to evict a node when all its children have been evicted?"
User development,
A new message was posted in the thread "How to evict a node when all its children
have been evicted?":
http://community.jboss.org/message/521362#521362
Author : Nicolas Filotto
Profile : http://community.jboss.org/people/nfilotto
Message:
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Hi All,
Since the last past days, I have been working on finding a memory leak in my program. I
finally identified it, in fact it is due to the fact that in JBC when all the sub nodes of
a JBC node are evicted, the parent node is never evicted even if it has not been declared
resident.
Let's take a concrete example
We assume that I have the following configuration
{code}
<eviction wakeUpInterval="5000">
<default algorithmClass="org.jboss.cache.eviction.FIFOAlgorithm"
eventQueueSize="1000000">
<property name="maxNodes" value="1" />
</default>
</eviction>
{code}
if I first call cache.put(Fqn.fromElements("1","1"),key,value)
If I then call cache.put(Fqn.fromElements("2"),key,value), the node
"/1/1" is evicted but its parent node "/1" is not evicted
If I then call cache.put(Fqn.fromElements("3"),key,value), the node
"/2" is evicted but node "/1" is still present.
This zombie node (i.e. node "/1") is the cause of my memory leak. So my question
is, is there a way to make JBC evicts those kind of nodes?
To limit the memory leak, I implemented a EvictionActionPolicy, but I would like to know
if there is a better solution. If I don't have any other way, could you check my code
below and tell me how I could improve it, because up to now, it fixes about 95% of the
memory leak but it seems that it doesn't work 100% of the time:
{code}
public class MyEvictionActionPolicy implements EvictionActionPolicy
{
Cache<?, ?> cache;
private static final Log log = LogFactory.getLog(DefaultEvictionActionPolicy.class);
public void setCache(Cache<?, ?> cache)
{
this.cache = cache;
}
public boolean evict(Fqn fqn)
{
boolean result;
try
{
if (log.isTraceEnabled()) log.trace("Evicting Fqn " + fqn);
cache.evict(fqn);
result = true;
}
catch (Exception e)
{
if (log.isDebugEnabled()) log.debug("Unable to evict " + fqn, e);
result = false;
}
try
{
Fqn parentFqn = fqn.getParent();
// My problem only occurs with the nodes under
if (parentFqn.size() == 2
&&
(parentFqn.get(0).equals(JBossCacheWorkspaceStorageCache.CHILD_NODES) ||
parentFqn.get(0).equals(
JBossCacheWorkspaceStorageCache.CHILD_PROPS)))
{
Node<?, ?> node = cache.getNode(parentFqn);
Set<Object> names = node.getChildrenNames();
if (names.isEmpty() || (names.size() == 1 &&
names.contains(parentFqn.get(1))))
{
cache.evict(parentFqn);
}
}
}
catch (Exception e)
{
if (log.isDebugEnabled()) log.debug("Unable to evict " + fqn, e);
}
return result;
}
}
{code
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