I wrote up a description of our multisite configuration https://meta.discourse.org/t/multiple-discourses-multiple-containers-one-server - a shared data container (data - one DB for each Discourse instance), and two app containers (web1 and web2), one for each Discourse instance.
I’ve had problems with aggregated CSS all along, but had both systems running reliably as 1.5.0beta6 (I ensured that each app instance had its own “shared” dir, so “shared1” for web1, and “shared2” for web2 - the data container stayed with the default “shared”).
After rebuilding all three containers to complete an upgrade to 1.5.0beta7, however, I saw a return of a problem I’ve had previous to beta6: every time I restart one app container (e.g. ./launcher restart web1), the other containers CSS (main and admin) starts to return a 404 (i.e. the site functions, but without CSS being applied). I also note that the __ws=[sitename] variable seems to be incorrect for both sites (the CSS for the site https://forums.oeru.org has __ws=community.oeru.org and https://community.oeru.org has __ws=forums.oeru.org).
Any thoughts on why this might be happening?
(Update: 2016-01-11 Ahh! Fixed it - see my comment below! tl;dr: you need one Redis instance per Discourse instance)