Instead of using the cache invalidation replication stream to invalidate
the _get_presence_cache, we can instead rely on the presence replication
stream. This reduces the amount of replication traffic considerably.
background_updates was using `call_later` in a way that leaked the logcontext
into the reactor.
We could have rewritten it to do it properly, but given that we weren't using
the fancier facilities provided by `call_later`, we might as well just use
`async.sleep`, which does the logcontext stuff properly.
A few non-functional changes:
* A bunch of docstrings to document types
* Split `EventsStore._persist_events_txn` up a bit. Hopefully it's a bit more
readable.
* Rephrase `EventFederationStore._update_min_depth_for_room_txn` to avoid
mind-bending conditional.
* Rephrase rejected/outlier conditional in `_update_outliers_txn` to avoid
mind-bending conditional.
... and update some docstrings to correctly reflect the types being used.
get_new_device_msgs_for_remote can return a long under some circumstances,
which was being stored in last_device_list_stream_id_by_dest, and was then
upsetting things on the next loop.
Currently we fetch the list of current state events whenever we send
something in a room. This is overkill for the common case of persisting
a simple chain of non-state events, so lets handle that case specially.
* `get_forward_extremeties_for_room` takes a numeric `stream_ordering`. We were
passing a `RoomStreamToken`, which meant that it returned the *current*
extremities, rather than those corresponding to the `from_token`. However:
* `get_state_ids_for_events` required a second ('types') parameter; this meant
that a `TypeError` was thrown and we ended up acting as though there was *no*
prev state.
* `get_state_ids_for_events` actually returns a map from event_id to state
dictionary - just looking up the state keys in it again meant that we acted
as though there was no prev state. We now check if each member's state has
changed since *any* of the extremities.
Also add/fix some comments.
