* Increase DB/CPU perf of `_is_server_still_joined` check.
For rooms with large amount of state a single user leaving could cause
us to go and load a lot of membership events and then pull out
membership state in a large number of batches.
* Newsfile
* Update synapse/storage/persist_events.py
Co-Authored-By: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
* Fix adding if too soon
* Update docstring
* Review comments
* Woops typo
Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
When a server leaves a room it may stop sharing a room with remote
users, and thus not get any updates to their device lists. So we need to
check for this case and delete those device lists from the cache.
We don't need to do this if we stop sharing a room because the remote
user leaves the room, because we track that case via looking at
membership changes.
Currently we rely on `current_state_events` to figure out what rooms a
user was in and their last membership event in there. However, if the
server leaves the room then the table may be cleaned up and that
information is lost. So lets add a table that separately holds that
information.
