Details
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Bug
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Status: Closed
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Critical
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Resolution: Fixed
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core 1.4.5
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None
Description
There are two places where transient state changes are merged with persisted state: 
in the SessionISM.stateModified call back method (typically called by a saving thread after it's changes have been saved) and (ii) in the SharedISM.Update.begin method. Sometimes the merge strategy fails in the sense that corrupt data is written to database.
How to reproduce:
The attached test program contains steps to reproduce the issue. The testInconsistency1 method concurrently adds a node D to a node A and moves child node B of A to another place. This sometimes results in a situation in which node A still has a child reference to node B whereas B has another parent. In this situation, Jackrabbit cannot be started anymore if the search index is missing:
Jun 8, 2009 2:16:23 PM org.apache.jackrabbit.core.query.OnWorkspaceInconsistency$1 handleMissingChildNode
SEVERE: Node /A (a7a29e8c-8d13-4fbd-b0ca-4f93f9c0ef42) has missing child 'B' (80aa13c5-1db6-4f62-b576-5e7f626d90c1)
Jun 8, 2009 2:16:23 PM org.apache.jackrabbit.core.RepositoryImpl initStartupWorkspaces
SEVERE: Failed to initialize workspace 'wm9'
The testInconsistency2 method concurrently adds a reference property to a node B (the threads do exactly the same). This sometimes results in a situation in which the referenced node can never be removed anymore because there is a "ghost" reference to it which cannot be removed. (It gives a ReferentialIntegrityException).
Jun 8, 2009 2:19:51 PM org.apache.jackrabbit.core.state.MLRUItemStateCache cache
WARNING: overwriting cached entry bc28ff87-216d-4ccd-bd73-03e7499ab54e/{}ref to B
Exception in thread "main" javax.jcr.ReferentialIntegrityException: 9f025634-d3e1-448e-904c-1c285f6b1bf6: the node cannot be removed because it is still being referenced.
It seems the first problem (the parent-child relation) is caused by an incorrect merge in the NodeStateMerger class. The second problem might also be caused by an incorrect or missed merge, but I am not sure whether that's the real problem.