This is essentially an implementation of the proposal made at https://hackmd.io/@richvdh/BJYXQMQHO, though the details have ended up looking slightly different.

This implements similar behavior to sytest where a matching branch is used,
if one exists. This is useful when needing to modify both application code
and tests at the same time. The following rules are used to find a matching
complement branch:

1. Search for the branch name of the pull request. (E.g. feature/foo.)
2. Search for the base branch of the pull request. (E.g. develop or release-vX.Y.)
3. Search for the reference branch of the commit. (E.g. master or release-vX.Y.)
4. Fallback to 'master', the default complement branch name.

When using a federation sender we'd send out all local presence updates over
federation even when they shouldn't be.

Fixes #10153.

Hopefully fixes #10027.

Spawned from missing messages we were seeing on `matrix.org` from a
federated Gtiter bridged room, https://gitlab.com/gitterHQ/webapp/-/issues/2770.
The underlying issue in Synapse is tracked by https://github.com/matrix-org/synapse/issues/10066
where the message and join event race and the message is `soft_failed` before the
`join` event reaches the remote federated server.

Less soft_failed events = better and usually this should only trigger for events
where people are doing bad things and trying to fuzz and fake everything.

Signed-off-by: Aaron Raimist <aaron@raim.ist>

This PR updates the build tags that we perform Complement runs with to match our [buildkite pipeline](https://github.com/matrix-org/pipelines/blob/618b3e90bcae8efd1a71502ae95b7913e6e24665/synapse/pipeline.yml#L570), as well as adding `msc2403` (as it will be required once #9359 is merged). Build tags are what we use to determine which tests to run in Complement (really it determines which test files are compiled into the final binary).

I haven't put in a comment about updating the buildkite side here, as we've decided to migrate fully to GitHub Actions anyhow.

This PR implements the ["Changes regarding the Public Rooms Directory"](https://github.com/Sorunome/matrix-doc/blob/soru/knock/proposals/2403-knock.md#changes-regarding-the-public-rooms-directory) section of knocking MSC2403.

Specifically, it:

* Allows rooms with `join_rule` "knock" to be returned by the query behind the public rooms directory
* Adds the field `join_rule` to each room entry returned by a public rooms directory query, so clients can know whether to attempt a join or knock on a room

Based on https://github.com/matrix-org/synapse/issues/6739. Complement tests for this change: https://github.com/matrix-org/complement/pull/72

This PR aims to implement the knock feature as proposed in https://github.com/matrix-org/matrix-doc/pull/2403



Signed-off-by: Sorunome <mail@sorunome.de>
Signed-off-by: Andrew Morgan <andrewm@element.io>

* Remove unused helper functions

* Clean up the interface for injecting opentracing over HTTP

* changelog

Fixes #10140

With the prior format, 1.33.0 / 1.33.1 / 1.33.2 got separate branches:

    release-v1.33.0
    release-v1.33.1
    release-v1.33.2

Under the new model, all three would share a common branch:

    release-v1.33

As before, RCs and actual releases exist as tags on these branches.

This better reflects our support model, e.g., that the "1.33" series had
a formal release followed by two patches / updates.

Signed-off-by: Dan Callahan <danc@element.io>

When joining a remote room limit the number of events we concurrently check signatures/hashes for (#10117)

If we do hundreds of thousands at once the memory overhead can easily reach 500+ MB.

Fixes #10123

Add a couple of extra logs/spans, to give a bit of a better idea.

... otherwise we tend to get a namespace clash between the bg process and the
functions that it calls.

Fixes #10121

Signed-off-by: Rohan Sharma <rhnsharma5113@gmail.com>

Signed-off-by: Chris Castle <chris@crc.io>

Fixes #1834.

`get_new_events_for_appservice` internally calls `get_events_as_list`, which will filter out any rejected events. If all returned events are filtered out, `_notify_interested_services` will return without updating the last handled stream position. If there are 100 consecutive such events, processing will halt altogether.

Breaking the loop is now done by checking whether we're up-to-date with `current_max` in the loop condition, instead of relying on an empty `events` list.


Signed-off-by: Willem Mulder <14mRh4X0r@gmail.com>

I hope this will improve
https://github.com/matrix-org/synapse/issues/9564.

If backfilling is slow then the client may time out and retry, causing
Synapse to start a new `/backfill` before the existing backfill has
finished, duplicating work.

Fixes #9956.

This adds quite a lot of OpenTracing decoration for database activity. Specifically it adds tracing at four different levels:

 * emit a span for each "interaction" - ie, the top level database function that we tend to call "transaction", but isn't really, because it can end up as multiple transactions.
 * emit a span while we hold a database connection open
 * emit a span for each database transaction - actual actual transaction.
 * emit a span for each database query.

I'm aware this might be quite a lot of overhead, but even just running it on a local Synapse it looks really interesting, and I hope the overhead can be offset just by turning down the sampling frequency and finding other ways of tracing requests of interest (eg, the `force_tracing_for_users` setting).

The existing tracing reports an error each time there is a timeout, which isn't
really representative.

Additionally, we log things about the way `wait_for_events` works
(eg, the result of the callback) to the *parent* span, which is confusing.

So that they render nicely in mdbook (see #10086), and so that we no longer have a mix of structured text languages in our documentation (excluding files outside of `docs/`).

[MSC2432](https://github.com/matrix-org/matrix-doc/pull/2432) added this endpoint originally but it has since been included in the spec for nearly a year. 

This is progress towards https://github.com/matrix-org/synapse/issues/8334