[MediaWiki-l] Fwd: Load balancing web servers and multimedia content

Jeremy Baron jeremy at tuxmachine.com
Tue Oct 28 13:19:43 UTC 2014

On Tue, Oct 28, 2014 at 8:33 AM, Justin Lloyd <jclbugz at gmail.com> wrote:
> Also, unless I'm missing something or being dense (it is late here), rsync
> simply wouldn't work since the upload directories are constantly being
> accessed and files written through one web server could easily be
> immediately accessed afterwards through another web server, and since there
> are four web servers (and possibly more or even less if I were to add AWS
> Auto Scaling into the mix), so keeping them all identical when writes could
> go through any of them would be pretty much impossible.

Well you don't have to limit yourself to having the file uploads
visible in only one part of the filesystem. (so this could work even
if you don't have dedicated storage hosts. mediawiki uses NFS mount
and unrelated vhost serves static files out of rsync target)

But you could also do like WMF (and it sounds like you already have
dedicated storage boxes?):
files are fetched from one hostname/varnish cluster/storage cluster
and HTML/etc. comes from a completely separate hostname/varnish
cluster/php cluster.

4 webservers mount rsync master by NFS. same as now. writes and file
description page rendering runs over NFS.

new webservers (or vhosts on existing webservers or webservers on the
storage hosts directly) serve images read-only from the local copy of
the files propagated by the rsync cron. (or whatever other way)

you could autoscale for the 4 webservers that don't have local images
at all (just NFS) and then either build an initial rsync into the
scale up process for storage hosts or do that scaling manually.

anyway, this is all just to address the immediate spof quickly. longer
term maybe figure out a way to use s3 or something. (which you could
do already actually. your rsync cron could instead be a copy to s3
cron. but then still spof on the same things where the config
described above would also have spof. e.g. file description pages,
uploading, deleting, etc.)


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