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From Joe Baldwin <jfbald...@earthlink.net>
Subject Re: Connection Pool
Date Sat, 17 Apr 2010 08:18:01 GMT
Well, Wikipedia claims that the recommended stable version is 5.1.45.  However, the webhost
claims that he has too many users to be able to upgrade  (which is a problematic answer since
this will mean he can never upgrade).

He is convinced (without any proof) that the problem lies with my code or with Cayenne. However
Michael was able to run his app configured for only two connections.  Furthermore there is
that innodb auto-increment lock bug clearly documented for MySQL 5.0.

I don't see any documented Cayenne bugs that could possibly cause these exceptions. My configuration
seems to be well within the norm (based on the recent posts).  That only leaves the documented
innodb bug.

Almost forgot, just prior to each one of the lock-exceptions an administrator was attempting
to add a new product to the database (which would certainly require interacting with innodb).

Question:
If the innodb bug is causing the lock-exception, would this then cause the ensuing connection
exception?  (Again, I cannot see how Cayenne or my nominal configuration could cause both
of these errors that are chronologically linked.)

Joe


On Apr 17, 2010, at 3:20 AM, Mike Kienenberger wrote:

> It looks like 5.0.90 is the latest 5.0 release, so I'd say that
> upgrading to at least would be a good start.
> 
> http://downloads.mysql.com/archives.php?p=mysql-5.0
> 
> It also says on that page that 5.0 is the oldest version currently supported.
> 
> 5.0.50a is from Jan 2008.
> 
> The most current version is 6.0, with major releases of 5.1, 5.2, 5.4, and 5.5.
> 
> While I haven't used mysql, I've seen a lot of postings about it over
> the years, and it's also very important that you have the most current
> jdbc driver for your version.
> 
> The only hit on this sql error in my personal cayenne archives is this
> 56-message thread from 2006.   Looks very relevant to your situation,
> although I've only glanced through it .  You can find it here.
> 
> http://www.mail-archive.com/cayenne-user@incubator.apache.org/msg00769.html
> 
> 
> On Sat, Apr 17, 2010 at 2:50 AM, Joe Baldwin <jfbaldwin@earthlink.net> wrote:
>> 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
>>> GPG fingerprint CBFB 84B4 738D 4E87 5E5C  5EFA EF6A 7D2E 3E49 102A
>> 
>> 


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