[MediaWiki-l] Mediawiki MySQL user-related database [dead]locks?

Andrew Smith asmith20 at littlesvr.ca
Sat Sep 17 18:32:19 UTC 2016


On 15/09/16 10:14, Andrew Smith wrote:
> On 15/09/16 07:08, Brian Wolff wrote:
>> locks). So maybe something is wrong on the php side. Thus I'd also
>> check the php error log, and maybe try enabling the MediaWiki debug
>> log and check that.
>
Thanks Brian. Your suggestion to turn on the MediaWiki debug log helped 
me track down the problem.

It was a bizarre one. wgSMTP was misconfigured and what happened was:

* Someone would try to register
* Mediawiki would start a transaction to do whatever in SQL, perhaps 
record that an account is being created
* Mediawiki would try to send an email, which I could see from a single 
log line with PEAR in it (the last log line for that request).
* The email would never get sent and the request to send the email never 
timed out (go figure).
* The transaction started way back when was never committed, and was 
left open forever.
* From that point on any other requests to modify user table timed out.

Why would one send an email in the middle of an SQL transaction? That's 
a disaster waiting to happen.

Is there a place where I should report this bug? I would like to help 
get this fixed, not just complain on my blog :) 
http://littlesvr.ca/grumble/2016/09/17/what-does-a-posix-signal-handler-and-an-sql-transaction-have-in-common/

It really sucks that I wasted so much time and patience dealing with 
this, but I'm glad I got it sorted out in the end. Thanks for the help 
Brian!

Cheers,

Andrew



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