[Mediawiki-l] Solution to caching problem (was: Re: New treeview skin ... caching problem ...)

[Netocrat]

A solution/workaround for the caching problem that I asked about as quoted
below.

It only seems to occur only after restoring a backed-up MediaWiki 1.5.8
database and then running maintenance/update.php from the 1.6.5 instance's
directory so that the later versions can also access this database.

The problem can be resolved when it occurs by running "php
rebuildMessages.php --rebuild" in the same maintenance directory.  There
doesn't seem to be a need to restart memcached.

On Wed, 10 May 2006 19:43:43 +1000, Netocrat wrote: [...]
> I'm encountering some MW + memcached problems on my development machine
> and before looking more closely wanted to run them by the list in case
> there's a quick answer like "that problem's expected with your set-up -
> do it differently".
> 
> I first noticed that intermittently the treeview's caching is failing -
> that the call to save its data structure to cache completes but on the
> next request the treeview is rebuilt again - a time-consuming operation
> - because the attempt to load it from cache comes up empty.  The problem
> seems to be related to a message that has recently started showing up in
> the debug log (many times per request when it appears, but sometimes not
> at all) as:
> memcached: Error parsing memcached response I later enabled memcached
> logging by setting $wgMemc->_debug true but a cursory look at the new
> output didn't give me any more insight.
> 
> Some information that might be relevant:
> 
> * I run several versions of MediaWiki on the one machine sharing a
> database (including table prefix) and memcached server.  No version in
> use is earlier than 1.5.8; the latest is a fairly up-to-date svn
> checkout. I haven't researched whether such a setup "should" work.  I
> have noticed (tangentially related) that some cache keys don't seem to
> include $wgDBprefix as a component.
> * The problem persists after restarting memcached and limiting browsing
> to one of the MediaWiki instances.
> * I encounter (and have been encountering for a long time prior to this
> problem) other occasional problems with messages showing up in html
> output as ###NONEXISTENT### that it's not simple to remedy - the
> interactions between messages in language files, in the database and in
> the message cache is something I've not yet looked closely at, and it's
> complicated by my addition and modification of messages in(to) php files
> whilst developing.  I'll have a closer look if there's no simple or
> quick explanation.
> * I recently installed eAccelerator on my development machine.  Prior to
> its installation I hadn't noticed this problem. * Cache settings in
> LocalSettings.php for each instance are:
>   $wgUseMemCached = true;
>   $wgMainCacheType = CACHE_MEMCACHED;
>   $wgMemCachedServers = array ( [identical server for each] );
>   $wgEnableParserCache = true;
[...]

-- 
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