[jbosscache-dev] Cache bean deployment via MC failing when TRACE enabled on org.jboss.kernel

[Galder Zamarreno]

Hi,

Bear with me on this one, it's a bit long :)

I've been running some tests creating Cache instances via MC and I've 
noticed that when TRACE logging is enabled on org.jboss.kernel, my Cache 
beans are not deployed whereas when org.jboss.kernel is set to DEBUG or 
higher, Cache beans deploy fine.

The error I'm getting is the following:

2009-03-03 21:40:51,505 ERROR [AbstractKernelController] (main) Error 
installing to Instantiated: name=CacheClusterA1 state=Described
java.lang.UnsupportedOperationException: Not supported in UnversionedNode
	at org.jboss.cache.AbstractNode.getChildrenDirect(AbstractNode.java:277)
	at 
org.jboss.cache.mvcc.NodeReference.getChildrenDirect(NodeReference.java:272)
	at 
org.jboss.cache.invocation.NodeInvocationDelegate.getChildrenDirect(NodeInvocationDelegate.java:163)
	at org.jboss.cache.DataContainerImpl.numNodes(DataContainerImpl.java:461)
	at 
org.jboss.cache.DataContainerImpl.getNumberOfNodes(DataContainerImpl.java:438)
	at org.jboss.cache.DataContainerImpl.toString(DataContainerImpl.java:394)
	at org.jboss.cache.DataContainerImpl.toString(DataContainerImpl.java:372)
	at 
org.jboss.cache.invocation.CacheInvocationDelegate.toString(CacheInvocationDelegate.java:144)
	at java.lang.String.valueOf(String.java:2615)
	at org.jboss.util.JBossStringBuilder.append(JBossStringBuilder.java:114)
	at 
org.jboss.dependency.plugins.AbstractControllerContext.toString(AbstractControllerContext.java:362)

Looks like in TRACE mode, MC is trying to print the Cache when this is 
not fully started.

To try to understand this, let's look at what DataContainerImpl logs 
when org.jboss.kernel is set to DEBUG:

log4j-jboss-kerneldebug.log:2894:2009-03-03 21:40:24,249 2198  TRACE 
[org.jboss.cache.DataContainerImpl] (main:) Starting data container. 
Using MVCC? false
log4j-jboss-kerneldebug.log:2895:2009-03-03 21:40:24,274 2223  TRACE 
[org.jboss.cache.DataContainerImpl] (main:) Setting root node to an 
instance of class org.jboss.cache.mvcc.NodeReference
...
log4j-jboss-kerneldebug.log:3038:2009-03-03 21:40:24,336 2285  TRACE 
[org.jboss.cache.DataContainerImpl] (main:) Starting data container. 
Using MVCC? true
log4j-jboss-kerneldebug.log:3039:2009-03-03 21:40:24,338 2287  DEBUG 
[org.jboss.cache.DataContainerImpl] (main:) Setting rootInternal to 
NodeReference{delegate=UnversionedNode[ /]}

After MVCC has been set to true, DataContainerImpl.getNumberOfNodes() is 
able to get the number of nodes successfully:

       if (!usingMvcc) return numNodes(root) - 1;
       return numNodesMvcc(rootInternal) - 1;

However, if in between the two "Starting data container" messages, 
someone (i.e. MC), tries to get the number of nodes (via toString), then 
Cache tries to get number of nodes of a MVCC node as a non MVCC node 
failing with the exception above. This is exactly what happens when you 
enable TRACE on MC kernel.

numNodesMvcc() calls getChildren(). numNodes calls getChildrenDirect().

With this TRACE enabled, log only show the first two lines:

log4j-jboss-kerneltrace.log:6731:2009-03-03 21:40:51,468 2817  TRACE 
[org.jboss.cache.DataContainerImpl] (main:) Starting data container. 
Using MVCC? false
log4j-jboss-kerneltrace.log:6732:2009-03-03 21:40:51,475 2824  TRACE 
[org.jboss.cache.DataContainerImpl] (main:) Setting root node to an 
instance of class org.jboss.cache.mvcc.NodeReference

So, how do we solve this?

I'm not sure I understand why DataContainerImpl.createRootNode() is 
called twice. The very first call, which seems to come from 
DataContainerImpl.injectDependencies() method (annotated with @Inject) 
looks suspicious. Why does it look suspicious? Because calls like this 
expect a config to be set. And when they're called initially from 
@Inject, the config object is not still set (when the call comes as part 
of the start operation, config is indeed set)

usingMvcc = config != null && config.getNodeLockingScheme() == 
NodeLockingScheme.MVCC;

And this returning false, when in fact the config is set to MVCC is what 
results of number of nodes being calculated incorrectly.

Not sure on how to fix this though.

Thoughts?
-- 
Galder Zamarreño
Sr. Software Maintenance Engineer
JBoss, a division of Red Hat
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