andrew at epstone
May 8, 2008, 6:00 AM
Post #4 of 5
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Re: [MediaWiki-CVS] SVN: [34358] trunk/extensions/CentralAuth
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On Thu, May 8, 2008 at 4:19 AM, Brion Vibber <brion [at] wikimedia> wrote:
> Detail: the s3 master (carrying centralauth DB) was stuffed with these reqs:
>
> SELECT /* Database::safeQuery */ gu_id, lu_dbname, gu_salt,
> gu_password,gu_auth_token,
>
> [.sorry, cut off as I didn't do a SHOW FULL PROCESSLIST]
>
>
> We were getting reports of a lot of "too many connections" errors on
> various wikis, mostly from people who *were* logged in but *not* with a
> merged account. With a merged account, or anonymous, I didn't seem to be
> having any problems.
>
>
> It looks like something was triggering a lot of extra lookups, which
> perhaps aren't getting properly cached.
>
I investigated this problem. Full details at [1].
Executive summary: resetState() is called from saveToCache if we don't
have fresh data from the master (i.e. if $this->mFromMaster is not
true). Unfortunately, if no row is found, that variable is not set to
true, whereas it is if a row IS found. I've put a patch for this
problem at the below link, which fixes it on my wiki. It's always the
one-liners ;-)
[1] https://secure.wikimedia.org/wikipedia/mediawiki/wiki/User:Werdna/CentralAuth_investigation
--
Andrew Garrett
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