* Trace event persistence

When we persist a batch of events, set the parent opentracing span to the that
from the request, so that we can trace all the way in.

* changelog

* When we force tracing, set a baggage item

... so that we can check again later.

* Link in both directions between persist_events spans

The stable prefixes have been supported since v1.34.0. The unstable
prefixes are not supported by any known clients.

* Room version 7 for knocking.
* Stable prefixes and endpoints (both client and federation) for knocking.
* Removes the experimental configuration flag.

Add 'federation_ip_range_whitelist'. This allows backwards-compatibility, If 'federation_ip_range_blacklist' is set. Otherwise 'ip_range_whitelist' will be used for federation servers.

Signed-off-by: Michael Kutzner <1mikure@gmail.com>

some cleanup, pulled out of #10134.

This is the first of two PRs which seek to address #8518. This first PR lays the groundwork by extending ResponseCache; a second PR (#10158) will update the SyncHandler to actually use it, and fix the bug.

The idea here is that we allow the callback given to ResponseCache.wrap to decide whether its result should be cached or not. We do that by (optionally) passing a ResponseCacheContext into it, which it can modify.

Synapse 1.36.0rc2 (2021-06-11)
==============================

Bugfixes
--------

- Fix a bug which caused  presence updates to stop working some time after a restart, when using a presence writer worker. Broke in v1.33.0. ([\#10149](https://github.com/matrix-org/synapse/issues/10149))
- Fix a bug when using federation sender worker where it would send out more presence updates than necessary, leading to high resource usage. Broke in v1.33.0. ([\#10163](https://github.com/matrix-org/synapse/issues/10163))
- Fix a bug where Synapse could send the same presence update to a remote twice. ([\#10165](https://github.com/matrix-org/synapse/issues/10165))

It turns out that we were sending the same presence state to a remote
potentially multiple times.

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.

It turns out that we were sending the same presence state to a remote
potentially multiple times.

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.