This expands the current shadow-banning feature to be usable via
the admin API and adds documentation for it.
A shadow-banned users receives successful responses to their
client-server API requests, but the events are not propagated into rooms.
Shadow-banning a user should be used as a tool of last resort and may lead
to confusing or broken behaviour for the client.
We have seen a failure mode here where if there are many in flight
unfinished IDs then marking an ID as finished takes a lot of CPU (as
calling deque.remove iterates over the list)
Introduced in #9104
This wasn't picked up by the tests as this is all fine the first time you run Synapse (after upgrading), but then when you restart the wrong value is pulled from `stream_positions`.
We do this by allowing a single iteration to process multiple rooms at a
time, as there are often a lot of really tiny rooms, which can massively
slow things down.
You can't continue using a transaction once an exception has been
raised, so catching and dropping the error here is pointless and just
causes more errors.
It's important that we make sure our background updates happen in a defined
order, to avoid disasters like #6923.
Add an ordering to all of the background updates that have landed since #7190.
This is another PR that grew out of #6739.
The existing code for checking whether a user is currently invited to a room when they want to leave the room looks like the following:
f737368a26/synapse/handlers/room_member.py (L518-L540)
It calls `get_invite_for_local_user_in_room`, which will actually query *all* rooms the user has been invited to, before iterating over them and matching via the room ID. It will then return a tuple of a lot of information which we pull the event ID out of.
I need to do a similar check for knocking, but this code wasn't very efficient. I then tried to write a different implementation using `StateHandler.get_current_state` but this actually didn't work as we haven't *joined* the room yet - we've only been invited to it. That means that only certain tables in Synapse have our desired `invite` membership state. One of those tables is `local_current_membership`.
So I wrote a store method that just queries that table instead
* Make this line debug (it's noisy)
* Don't include from_key for presence if we are at 0
* Limit read receipts for all rooms to 100
* changelog.d/8744.bugfix
* Allow from_key to be None
* Update 8744.bugfix
* The from_key is superflous
* Update comment
