Am 21.07.2006 um 17:16 schrieb Gentry, Michael ((Contractor)):
Glad it is working right now. Are you using the new MySQL adapter
Andrus put together for you?
No, not yet. We thought we will give it a try next week.
Yes, Cayenne will catch the exception for the lost connection and
try to
automatically reconnect. That might be better than the JDBC driver
auto-reconnecting, since Cayenne will know something "bad"
happened. I
don't know that this feature is documented anywhere. I discovered
it by
accident. I was testing my application on my laptop and had left it
running inside Eclipse. When I went home, I put the laptop in standby
mode totally forgetting about the application. Came back the next
morning and tried using the application again and saw an exception
with
Cayenne handling it and automatically reconnecting. This also works
well in deployment, since it will auto-reconnect when the DB server is
rebooted.
That behaviour does fit perfectly to the picture we experienced. It
seems as if
the mysql connection is lost from time to time and that the mysql jdbc
driver did reconnect "in the background" automatically. Giving
Cayenne no
chance to recognize the lost. Cayenne would in that case continue to
work
and in the meantime some other process grabbed the same package of
primary keys
and our problems started.
Besides, I still haven't seen any "Duplicate key" messages from our
systems!
Thanks to all for this helpful discussion!
Christian
/dev/mrg
-----Original Message-----
From: Christian Mittendorf [mailto:[EMAIL PROTECTED]
Sent: Friday, July 21, 2006 11:09 AM
To: [email protected]
Subject: Re: Duplicate Key Problem
Am 21.07.2006 um 16:14 schrieb Gentry, Michael ((Contractor)):
4.0.12 of MySQL. I think autoReconnect=false is a good thing to try,
since Cayenne will catch connection exceptions and try to
reconnect on
its own.
From what I can see so far, after we updated all apps some hours
ago, it
seems to be working fine.
How would Cayenne handle a lost connection? Would that result into an
Exception or would Cayenne take care, try to reconnect and try to
work as
expected?
Is there some documentation available or do I have to play "Read the
source, Luke", as Obi-Wan liked to say ;-)
Thanks and have a nice weekend!
Christian
Thanks,
/dev/mrg
-----Original Message-----
From: Christian Mittendorf [mailto:[EMAIL PROTECTED]
Sent: Friday, July 21, 2006 9:56 AM
To: [email protected]
Subject: Re: Duplicate Key Problem
Am 13.07.2006 um 20:35 schrieb Andrus Adamchik:
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.
May it be that the version of MySQL has some affects on what we
experience? We are currently using 5.0.18.
I am curious what Michael finds in his tests.
Me too, are there any results available?
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.
We will update some applications in the next week, we haven't found
the time to do so this week.
But there was some other idea we had discussed recently. At the
moment all of our apps use the "autoReconnect=true" feature of the
jdbc driver and after some discussions with colleagues we updated the
config to use "autoReconnect=false". If our problem is related to
MySQL loosing the connection I would expect to get some kind of "Lost
connection" errors instead of duplicate key messages.
Christian
