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From "Martijn Hendriks (JIRA)" <j...@apache.org>
Subject [jira] Created: (JCR-2129) Prevent data inconsistencies due to missed merges in the SharedItemStateManager
Date Sat, 06 Jun 2009 18:54:07 GMT
Prevent data inconsistencies due to missed merges in the SharedItemStateManager
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                 Key: JCR-2129
                 URL: https://issues.apache.org/jira/browse/JCR-2129
             Project: Jackrabbit Content Repository
          Issue Type: Bug
          Components: jackrabbit-core
    Affects Versions: core 1.4.5, 2.0.0
            Reporter: Martijn Hendriks
            Priority: Critical


The SharedItemStateManager.Update class's begin method tests whether states in the given local
ChangeLog are stale. If so, it tries to merge the changes to the new persisted state. It does
this by comparing the modCount of state instances for non-transient states. There is a race
between two threads that call save such that sometimes this test fails and states are not
merged when they should be. As a result, the data in the repository can become corrupt and,
for instance, it becomes impossible to start Jackrabbit or remove certain nodes.

Analysis: persisted state information, including modCount, is pushed down from another thread
while a local ChangeLog is being constructed. The increased modCount thus appears in the local
ChangeLog and the SharedISM falsely assumes that the state in the local ChangeLog needs no
merging (isStale test).

Reproduction:
The attached test program contains steps to reproduce the issue (see comments of the testInconsistency1
and testInconsistency2 methods).



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