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From "Unico Hommes (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (JCR-3290) Concurrent add and move can cause inconsistency
Date Tue, 10 Apr 2012 16:41:17 GMT
Concurrent add and move can cause inconsistency
-----------------------------------------------

                 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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