[jboss-jira] [JBoss JIRA] Commented: (JBAS-6587) Unnecessary Locking in WrappedConnection and WrappedPreparedStatement

[Christian Naeger (JIRA)]

    [ https://jira.jboss.org/jira/browse/JBAS-6587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12493276#action_12493276 ] 

Christian Naeger commented on JBAS-6587:
----------------------------------------

Hi Adrian, 

this issue is closed, so I don't know if my comment reaches you. 
I also used YourKit to profile an app deployed on a JBoss 4.2.3 with an underlying MySQL database. 

Basically all stack traces where time is spent boil down to the following:

<pre>
-> our stuff
--> some Hibernate method							time spent so far: 1%
----> org.jboss.resource.adapter.jdbc.WrappedPreparedStatement.executeQuery()	time spent in this method: 95%
-------> net.sourceforge.jtds.jdbc.JtdsPreparedStatement.executeQuery()		time spent in this method: 4%
</pre>

The interesting thing now is that 95% of the time is spent in WrappedPreparedStatement, BUT ONLY 4% in JtdsPreparedStatement.executeQuery(). 
So it looks as if 95% of the time is spent inside Jboss and only 4% in the actual query to the database!!!

This also complies with the observation that our application is terribly slow, but the database load is still quite low.

I debugged into org.jboss.resource.adapter.jdbc.WrappedPreparedStatement.executeQuery() to see where this time could have been spent and I have the suspicion it is in the synchronized(stateLock) block of the following method (called from WrappedPreparedStatement.executeQuery()):

org.jboss.resource.adapter.jdbc.BaseWrapperManagedConnection.checkTransaction()

So is this really the desired behaviour? Or are we doing something completely wrong (likely :-)?

Any help is highly appreciated!

Regards, 
Christian Naeger


> Unnecessary Locking in WrappedConnection and WrappedPreparedStatement
> ---------------------------------------------------------------------
>
>                 Key: JBAS-6587
>                 URL: https://jira.jboss.org/jira/browse/JBAS-6587
>             Project: JBoss Application Server
>          Issue Type: Feature Request
>      Security Level: Public(Everyone can see) 
>          Components: JCA service
>         Environment: Windows 
> Sun JDK 1.6
>            Reporter: Deyan Bektchiev
>            Priority: Minor
>
> The JBoss JDBC Connection and PreparedStatement wrapper classes all acquire and release a lock when entering and exiting most of their methods.
> JDBC connections are not supposed to be thread safe and even if you coded your wrapper this way there is no guarantee that the underlying Connection would behave properly if accessed by multiple threads concurrently.
> In one particular use case when profiling obtaining the locks for Statements (that obtain the Connection locks) took 5% of the total time.
> I can provide a YourKit CPU profiler snapshot.
> Regards,
> Deyan

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