Concurrent add and move can cause inconsistency
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Key: JCR-3290
URL: https://issues.apache.org/jira/browse/JCR-3290
Project: Jackrabbit Content Repository
Issue Type: Bug
Affects Versions: 2.4, 2.2.11
Reporter: Unico Hommes
Priority: Critical
Fix For: 2.2.12, 2.4.2
Attachments: AddMoveTest.patch
The scenario is as follows:
We start out with the following repository structure:
/folder1/node1
/folder2
Session s1 modifies /folder1 (for instance set a property or add a node, it
doesn't matter, as long as it creates a transient item state for /folder1)
Session s2 moves /folder1/node1 to /folder2/node1
Session s2 does a save
Session s1 modifies /folder2/node1 (for instance set a property or add a node,
it doesn't matter, as long as it creates a transient item state for node2)
Session s1 does a save
The repository is now inconsistent: /folder1 has a child node entry for node1
whereas node1 has parent id for /folder2
The problem is in the NodeStateMerger.merge method. When on s1.save a merge is
attempted on the child node entries of /folder1 the transient state has a child
node entry for node1 (which was actually moved to /folder2). This expected. The
merger decides to add this node if one of two conditions is true: the child
node entry is either in the added set of the change log or it is in the
modified set of the change log (the latter because the child node will be in
the modified set if it was moved to this node). The latter condition is the
problem. Because node1 was modified it is indeed in the modified set and thus
added.
However it has a different parent id (the parent id of the folder it was moved
to). That means that /folder1 is saved with a child node entry for node1.
Attached is a test case that shows that the above scenario leads to an
inconsistency.
Also attached is a proposal for a fix. The patch modifies the semantics of
NodeStateMerger.MergerContext#isAdded somewhat: it returns true if either the
child is in the added set or it is both in the modified set and its parent is
the state that is currently being merged. Perhaps the method should be renamed
to isAddedTo instead of just isAdded.
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