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From "Micah Whitacre (JIRA)" <j...@apache.org>
Subject [jira] Created: (JCR-2197) Support configuration of timeout in Statements for Database implementations
Date Wed, 08 Jul 2009 22:13:14 GMT
Support configuration of timeout in Statements for Database implementations
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                 Key: JCR-2197
                 URL: https://issues.apache.org/jira/browse/JCR-2197
             Project: Jackrabbit Content Repository
          Issue Type: Bug
          Components: locks
    Affects Versions: 1.5.6
            Reporter: Micah Whitacre


Allowing for the configuration and usage of a timeout value for Statements[1] would provide
a means avoiding dead lock when a long running/stalled SQL Statement holds onto a lock preventing
other threads from acquiring locks.  

The situation i have seen is where a JVM handling multiple request each in its own Thread
will at some points become stalled.  At the start of each thread processing the request it
will acquire its own session to the repository which stores all information in an an Oracle
database.  The issue we are seeing is that deadlock occurs because the SQL write statement
to the VersionManager is taking too long/stalling in the Oracle driver code.  Since it is
writing, the write lock is acquired and this prevents other threads from acquiring a session
because they get blocked trying to acquire the read lock of the Version Manager.

If the SQL statement timed out after a certain time, this would alleviate the problem of threads
continually hanging and make use of the Jackrabbit auto reconnect functionality.  The user
of timeout is supported when using JNDI so this request would move it towards being first
class support on the database implementations.

[1] - http://java.sun.com/j2se/1.5.0/docs/api/java/sql/Statement.html#setQueryTimeout(int)
[2] - http://forums.sun.com/thread.jspa?threadID=343023&start=30&tstart=0

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