On Jun 12, 2008, at 10:07 AM, jfjames wrote:
In parallel to this DBCP patch, I've developped an OpenEJB service
in order
to use C3P0. My objective is to have a fallback solution in
production in
case of problem with DBCP. Everything works fine (very good exercice
to
understand how OpenEJB configuration works internally ... to be
honest I
must admit there is still some mystery around XBean in my
understanding) ,
except that no commit/rollback are sent to the database. This may be
due to
the fact that C3P0 doesn't support distributed transaction and its
connections are not enrolled by the TransactionManager (no
implementation of
ManagedConnection). There is the same issue with Proxool. Do you
know any
alternative to DBCP which could be used with OpenEJB ?
There's the Geronimo connection manager, but I'm not aware of anything
else. DBCP also didn't support any concepts related to transaction
handling either and we had to add all that so we could use it in
OpenEJB. It was one of Dain's mini side efforts that took a few weeks.
Feel free to ask for xbean info of any kind on the dev list.
-David
jfjames wrote:
OK, we've opened a DBCP JIRA issue :
https://issues.apache.org/jira/browse/DBCP-269.
It would be very nice to include this patch in OpenEJB 3.0.1.
-JF
David Blevins wrote:
On Jun 11, 2008, at 4:44 AM, jfjames wrote:
We're back ... It seems we’ve identified the cause of the problem.
It is
located in DBCP 1.3. In fact, the isClosed method of the
DelegatingConnection class doesn’t really close the underlying JDBC
connection :
* when called from the destroyObject method of the
PoolableConnectionFactory, the _closed variable is set to false,
* therefore the test if ( _closed || _conn.isClosed() ) doesn’t
allow to
propagate the close along the delegating chain (up to the JDBC
connection).
According to us, it should be replaced by if ( _closed &&
_conn.isClosed()
). We’ve done some tests with this patch and it works fine :
maxActive is
never exceeded and the number of connections to the database
server is
stable.
Now, we have to check the impact on the DBCP jUnit tests before
going
further ...
Great work! Going to be a fantastic contribution.
Once you're confident on the impact to the dbcp unit tests, craft
up a
patch file and open up a JIRA for the issue at
http://issues.apache.org/jira/browse/DBCP
I can help you with instructions on creating patches if you need it
(just an "svn diff > myPatch.txt" for the most part). Then I can go
tap those guys on the shoulder and let em know we're waiting on it
and
it's critical for us.
If we can get them to commit it we won't need to wait for a DBCP
release and can just roll up a custom build that we can use in
3.0.1.
-David
jfjames wrote:
We've spent some time today investigating what actually happens in
the
DataSource ... Not so easy since DBCP code is a little tricky !
We've observed that JDBC connections which are realeased from the
pool by
the Evictor are not physically closed :
1/ from the DataSource standpoint : the maximum size of the pool
is
never
exceeded (numActive is always inferior to maxActive),
2/ but from the dataserver standpoint : the number of
connections is
always increasing (up to the maximum allowed by the server).
We haven't identified the exact cause of this issue : for some
unknown
reason the DelegatingConnection.close() method consider the JDBC
connection as already closed which is wrong.
Next step tomorrow ...
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