* Fix deprecation warnings due to invalid escape sequences.

* Add changelog

Signed-off-by: Karthikeyan Singaravelan <tir.karthi@gmail.com>

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

As mentioned in #7397, switching to a debian base should help with multi-arch work to save time on compiling. This is unashamedly based on #6373, but without the extra functionality. Switch python version back to generic 3.7 to always pull the latest. Essentially, keeping this as small as possible. The image is bigger though unfortunately.

It serves no purpose and updating everytime we write to the device inbox
stream means all such transactions will conflict, causing lots of
transaction failures and retries.

Fixes #7774

It's somewhat expected for us to have unknown room versions in the
database due to room version experiments.

I'm pretty sure there's no technical reason these have to be distinct server blocks, so collapse into one and go with the more terse location block.

Signed-off-by: Luke W Faraone <luke@faraone.cc>

When we get behind on replication, we tend to stack up background processes
behind a linearizer. Bg processes are heavy (particularly with respect to
prometheus metrics) and linearizers aren't terribly efficient once the queue
gets long either.

A better approach is to maintain a queue of requests to be processed, and
nominate a single process to work its way through the queue.

Fixes: #7444

We shouldn't allow others to make_join through us if we've left the room;
reject such attempts with a 404.

Fixes #7835. Fixes #6958.

This reuses the same scheme as federation sender sharding

Fix guest user registration with lots of client readers

I found these made pycharm have more of a clue as to what was going on in other places.

partly just to show it works, but alwo to remove a bit of code duplication.

It was correct at the time of our friend Jorik writing it (checking
git blame), but the world has moved now and it is no longer a
generator.

Signed-off-by: Olivier Wilkinson (reivilibre) <olivier@librepush.net>

When considering rooms to clean up in `delete_old_current_state_events`, skip
rooms which we are creating, which otherwise look a bit like rooms we have
left.

Fixes #7834.

* Fix client reader sharding tests

* Newsfile

* Fix typing

* Update changelog.d/7853.misc

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

* Move mocking of http_client to tests

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

As far as I can tell from the sentry logs, the only time this has actually done
anything in the last two years is when we had two master workers running at
once, and even then, it made a bit of a mess of it (see
https://github.com/matrix-org/synapse/issues/7845#issuecomment-658238739).

Generally I feel like this code is doing more harm than good.