This is a known bug - users with multiple boxes would have to rsync the config files over, and purge tmp/*

The config file is necessary to store Super user settings and allow override of other settings from global.ini.php

can you think of a solution that we could implement in Piwik to make it a non issue, or is it a won't fix?

Use bootstrap.php to define PIWIK_USER_PATH -- and point it at a shared network directory to host the config and tmp folders.

Future idea:

• post an event when config file or cache files are removed/updated.
• add a plugin that:
  • keeps track of the machines in the cluster
  • listens for the event and notifies other machines in the cluster via a REST API method
  • has a REST API method to invalidate its cache (eg software update) or specific cache files (eg cache/tracker)

Well, as I'm having the same issue I wouldn't recommend to build some complex thing like tracking machines in a cluster and pushing changes to it.
Just do some simple things:

• to avoid session issues on login use some other session backend like memcache (can be done on the user side, not your part to change that)
• store settings which change during runtime like enabled/disabled plugins in the database (I currently just reload the site over and over until all nodes picked up the change). Usually only installation critical settings like database settings are stored in the files.

Pushing an update requires less resources.

If we move the config (except db connection info and maybe superuser), we'd have to maintain lastModified timestamps for the config and site tables, so machines could determine if they need to refresh cache files or not. Adding this query to the tracker would impair tracker performance.

The session issue is covered by another ticket.

I think a wont fix for now. It makes sense to tie config file to enabled plugins and database infos.