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From "Jukka Zitting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-1440) NPE Thrown when two Cluster Nodes are hitting the same underlying database.
Date Fri, 19 Feb 2010 16:36:28 GMT

    [ https://issues.apache.org/jira/browse/JCR-1440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12835807#action_12835807
] 

Jukka Zitting commented on JCR-1440:
------------------------------------

I'm sorry about the long inaction on this issue.

I've now committed Ryan's patch, as it seems to solve the immediate issue. The solution however
seems a bit hacky and reminds me of the double-checked locking antipattern. It would be better
if the caches were loaded only on-demand and correctly invalidated on cluster changes. Or
perhaps we could drop the version history caches entirely, as the underlying item state managers
should already take care of the performance impact.

> NPE Thrown when two Cluster Nodes are hitting the same underlying database.
> ---------------------------------------------------------------------------
>
>                 Key: JCR-1440
>                 URL: https://issues.apache.org/jira/browse/JCR-1440
>             Project: Jackrabbit Content Repository
>          Issue Type: Bug
>          Components: clustering, jackrabbit-core
>    Affects Versions: 1.4, core 1.4.1
>         Environment: Vista JDK 1.5.0_12.  Using Derby and Derby Client 10.1.2.1
>            Reporter: Micah Whitacre
>            Assignee: Jukka Zitting
>            Priority: Critical
>         Attachments: jackrabbit-1.5-JCR-1440.tar.gz, jcr-1440-workaround.patch, repository1.xml,
SimpleJackrabbitConflictTest.java, SimpleJackRabbitTest.zip
>
>
> I've created a test that creates two repositories with clustering enabled that are backed
by the same database.  Using the following workflow causes a NullPointerException to be thrown.
> The workflow I'm using is:
> The root node is versioned.
> ClusterNode1 creates a versioned child node named "foo".
> The test waits to make sure the syncDelay has passed so ClusterNode2 will notice the
newly created node.
> ClusterNode2 retrieves the "foo" child node and removes it.
> The test waits for the change ClusterNode1 to sync with that change.
> ClusterNode1 tries to create another new node however a NullPointerException is thrown
when the it tries to checkout the rootNode.
> java.lang.NullPointerException: null values not allowed
> 	at org.apache.commons.collections.map.AbstractReferenceMap.put(AbstractReferenceMap.java:251)
> 	at org.apache.jackrabbit.core.version.VersionManagerImpl.getItem(VersionManagerImpl.java:280)
> 	at org.apache.jackrabbit.core.version.XAVersionManager.getItem(XAVersionManager.java:334)
> 	at org.apache.jackrabbit.core.version.AbstractVersionManager.getVersion(AbstractVersionManager.java:87)
> 	at org.apache.jackrabbit.core.NodeImpl.getBaseVersion(NodeImpl.java:3198)
> 	at org.apache.jackrabbit.core.NodeImpl.checkout(NodeImpl.java:2991)
> 	at com.cerner.system.configuration.repository.jcr.SimpleJackrabbitConflictTest.testNullPointerExceptionThrown(SimpleJackrabbitConflictTest.java:96)

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