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

Andrew Smith asmith20 at littlesvr.ca
Thu Sep 15 14:14:10 UTC 2016


On 15/09/16 07:08, Brian Wolff wrote:
> I don't know much about DB locking, so the following might be stupid and wrong:
>
> I was under the impression that mysql would add a line like "-------
> TRX HAS BEEN WAITING 4 SEC FOR THIS LOCK TO BE GRANTED:" if the
> transaction is actually waiting for a lock. So the output of show
> innodb engine status you pasted above makes me almost think that its
> not so much mediawiki is waiting for a lock as MW is holding a bunch
> of locks, and for some reason never sending a commit (This might be
> the totally wrong conclusion, I don't really know anything about mysql
> 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.

That's exactly what I was expecting! But the transaction will literally 
never die, it will stay there for hours (days if I let it).

I've had the following set fora while:

$wgShowExceptionDetails = true;
$wgShowSQLErrors = true;
$wgDebugDumpSql  = true;
$wgDBerrorLog = true;

But I don't see any extra logs in the server error logs. I do get the 
sql error in the web interface when it times out.

I will set $wgDebugLogFile and see if that shows anything.

What else could I do? Surely it's not a bug in mediawiki, I wouldn't be 
the first to notice :) It's got to be related with my setup or my data?

Thanks,

Andrew



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