I've tried many times so far and haven't been able to get duplicate keys
across two applications (different VMs in this case). This comment from
Christian sounded a bit extreme to me, though:
"The db has collected 3893813 connection attempts and 534 aborted
clients
since we restarted the db two days ago."
A normal Cayenne application would generate very few connection
attempts. 3.8 million in 2 days? That's 2700 connections/minute. That
is a LOT. (My Tapestry-based application probably does 1-2
connections/database per week, depending on load/etc.) I wonder if
MySQL could be stuttering or having a few issues under that kind of
load?
/dev/mrg
-----Original Message-----
From: Andrus Adamchik [mailto:andru..bjectstyle.org]
Sent: Thursday, July 13, 2006 2:36 PM
To: cayenne-use..ncubator.apache.org
Subject: Re: Duplicate Key Problem
BTW, I tried to reproduce PK generator getting an incorrect PK range
on MySQL by emulating some load via JMeter. It never happens (at
least on a single VM instance). I wrote a test case that throws an
exception randomly on committing the user transaction. Still the
application was able to recover from failed transactions and carry on
processing other requests.
I am curious what Michael finds in his tests.
Anyways, I went ahead and added an explicit commit to the PK
generator (that code, although I couldn't make it fail, still looked
suspect) and posted new jars here:
http://dev.objectstyle.org/~andrus/cayenne-07132006/
Christian, I would appreciate if you could try this in your
application and see if you still get those errors.
Andrus
On Jul 13, 2006, at 11:53 AM, Andrus Adamchik wrote:
> Cool, I'll wait for the results.
>
> Andrus
>
>
> On Jul 13, 2006, at 11:44 AM, Gentry, Michael ((Contractor)) wrote:
>
>> The quickest way to test that I can think of is to be stepping
>> through
>> the PK generation code in the debugger and after you lock/select the
>> PKs, use "mysqladmin kill" to kill your connection before the
>> update/unlock. You can then try to access the auto_pk_support table
>> from another app (or the mysql prompt) and see if it is still
>> locked/etc. I might could use my CayenneExample (with a few
>> tweaks) to
>> test this in a bit.
>>
>> /dev/mrg
>>
>>
>> -----Original Message-----
>> From: Andrus Adamchik [mailto:andru..bjectstyle.org]
>> Sent: Thursday, July 13, 2006 11:23 AM
>> To: cayenne-use..ncubator.apache.org
>> Subject: Re: Duplicate Key Problem
>>
>>
>>
>> On Jul 13, 2006, at 10:57 AM, Gentry, Michael ((Contractor)) wrote:
>>
>>> Is the PK cache per VM or per DataNode? I was thinking per DataNode
>>> (obviously within the same VM, of course).
>>
>> True, more accurately it is one per DataNode, and is shared by all
>> DataContexts that sit on top of a given DataDomain.
>>
>>
>>> Another thing that could be tricky is that the MySQL JDBC connector
>>> (Connector/J) has an autoReconnect=true option, which would catch a
>>> disconnection before Cayenne could see it and reconnect. Not
>>> sure at
>>> all what would happen to an in-progress transaction if that were the
>>> case.
>>
>> Good point. But I am more concerned about runtime exceptions in the
>> code that theoretically can cause a PK range to become invalid. One
>> straightforward way to fix that is to apply the same approach we did
>> for Sybase PK generator per CAY-588 (i.e. ensure that PK is generated
>> outside of the main transaction. I guess that's what we'll have to
>> do, but I want to have a way to reproduce the problem first, if only
>> to know that our fix actually fixes it.
>>
>> Andrus
>>
>
>
This archive was generated by hypermail 2.0.0 : Thu Jul 13 2006 - 14:52:18 EDT