[mythtv-users] MySQL related BE deadlocks - collective wisdom needed

Warpme warpme at o2.pl
Fri Aug 5 07:44:37 UTC 2011

On 8/4/11 10:39 PM, Michael T. Dean wrote:
> Thought I'd mention that Daniel K just pushed a change that reworks
> reconnections.  It removes the MySQL-library provided auto-reconnect
> that I just put in (for the exact same reasons MySQL changed their API
> to disable auto-reconnect--because it can't work with certain
> application designs, and MythTV has changed since 0.21 to a design where
> auto-reconnect cannot work).  So there's no need for further testing
> that patch.
> We have high hopes that this will work around the frequent MySQL
> connection drop-out issues some users were seeing.  And I'd still be
> very interested to hear details if anyone can identify the specific
> MySQL server/client library configuration that's causing these frequent
> drop outs.
> If you're running master, please pull an update (to 4dfcdb8dd0c80 or
> later), and please report back if it helps.  For those of you on
> 0.24-fixes, I will try to create a backport patch and post it here for
> testing later today.  We plan to let this sit in unstable for a bit of
> testing and to prove it actually works before pushing it to -fixes, though.
> Mike
> _______________________________________________
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Daniel, Mike,

Milion thx You are working on this issue !
At some point of time I was almost sure issue is my specific and I can't 
expect You will loose time on this particular one.

Browsing Internet I can't find any bug reports describing issue like 
mine. Taking into account mysql popularity - it seems like mine problem 
root cause isn't within mysqlclient lib itself but rather in 
environment/app which uses this lib.

Last days I upgrade switch back to MyISAM+upgrade to 5.5.15. With this 
change - I still have at least deadlock per day (with famous stack trace).
So by this, 2 days ago I decided to do in one steep full 
reinstall+upgrade ALL system packages. Now I'm on tests phase.
As I'm trying to find root cause - I want to test one change at time, so 
I will apply Daniel's commits as soon as I will have first deadlock.

BTW: What I observe: this lib is reentrant and I see, during hang, other 
treads successfully accessing DB. It looks like lib hangs are only in 
context of given thread.
Looking for hangs in vio_net I found interesting thread on mysql forums: 
It is related to lib crash not hang but with quite similar stack trace - 
so maybe it is somehow correlated ?


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