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From Joe Baldwin <jfbald...@earthlink.net>
Subject Re: Connection Pool
Date Sat, 17 Apr 2010 06:50:21 GMT
Ari,

> Very many people have stayed on the 5.0.x releases due to perceived problems with 5.1.x.
There is nothing in either of those releases that should make the slightest difference to
Cayenne.


I did some more research and found a report with *similar* symptoms

	http://bugs.mysql.com/bug.php?id=16979

The complaint is that in an early 5.0 MySQL:

	"When accessing the auto-increment counter, InnoDB uses a special table-level AUTO-INC lock
that it keeps to the end of the current SQL statement, "

This appears to document anomalous locking behavior associated with MySQL 5.0 innodb, that
the subsequent postings suggest will be fixed in 5.1.  If this is in fact table level locking
then a simple update could cause problems when there are multiple users reading & writing
data.  (I have no idea how to reproduce this, or test the extent to which the innodb locking
has cascading affects, however if this could cause connection problems then it could be the
culprit)

You guys know way more about DBMS behavior than I; does this sound like it could be the problem
(remember the logs show the locking exception is typically just prior to the connection exception)?

If so, then a simple upgrade to MySQL 5.1 might fix the problem.

Thanks,
Joe




On Apr 16, 2010, at 10:51 PM, Aristedes Maniatis wrote:

> On 17/04/10 11:49 AM, Joe Baldwin wrote:
>> the database is running on a production machine:
>> 
>>   Sun MySQL - 5.0.51a
>>   Linux 2.6.25-14.fc9.x86_64 (amd64)
>>   Java 1.6
>> 
>> One thing I noticed was that my webhost is using MySQL 5.0.51a, while Wikipedia documents
5.1.45 as the most recent stable release.  The JDBC driver is provided by the host.
>> 
>> I am not sure why they are using 5.0.51a. Could this cause a problem with Cayenne?
> 
> 
> Very many people have stayed on the 5.0.x releases due to perceived problems with 5.1.x.
There is nothing in either of those releases that should make the slightest difference to
Cayenne.
> 
> You should look at running a recent version of the JDBC driver.
> 
> Ari
> 
> 
> -- 
> -------------------------->
> Aristedes Maniatis
> ish
> http://www.ish.com.au
> Level 1, 30 Wilson Street Newtown 2042 Australia
> phone +61 2 9550 5001   fax +61 2 9550 4001
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