On Mon, Jun 16, 2014 at 9:08 AM, Daniel Barrett <danb(a)vistaprint.com> wrote:
In the past few weeks, we've been seeing the
"Loss of session data" error message in our wiki frequently when users try to
save their edited articles (and the save fails). Our best guess is that memcached, which
stores session info, is losing session information unexpectedly. This began shortly after
upgrading from MediaWiki 1.21 to 1.22 (I don't know if this is related, but the timing
is suspicious). When users log out and log back in, the error goes away... for a time.
What is the recommended way to debug this kind of problem? What would YOU do if this
issue cropped up on your wiki?
We've been inserting error_log() statements into MediaWiki core code, dumping the
values of $_SERVER, $_COOKIE, and $_SESSION, and haven't found anything helpful yet.
Our wiki (version 1.22.5) is served by four webservers behind a load balancer on a
private intranet. There's a master and one slave database. memcached has plenty of
RAM and therefore should not be dropping data.
Is memcached setup to use all of the memory? You can get pretty good
stats out of it (or used to, bad in my ops days). That prove it's not
dropping things out of cache.
Also, make sure it's not a mismatch of the edit token (which is
several places gives an error saying the session was lost, but could
be because the session token was actually updated, like if the user
logs out from another browser.
Thanks for any helpful debugging tips!
DanB
_______________________________________________
MediaWiki-l mailing list
MediaWiki-l(a)lists.wikimedia.org
https://lists.wikimedia.org/mailman/listinfo/mediawiki-l