@david has been investigating, we do confirm that as it stands 2gb is enough for docker rebuilds, but not enough for the web upgrader to work.
One idea I have tossed around is just shutting down all ruby processes during the web upgrader to save an extra 300-500mb which would leave enough for asset precompilation.
A long term approach we are likely going to need to go down for self hosters is shipping bootstrapped containers which is a pandoras box cause how would a web upgrader be able to pull that one off. We don’t want to mount docker sockets …
it sure is a pickle.