* Refactor Keyring._start_key_lookups

There's an awful lot of deferreds and dictionaries flying around here. The
whole thing can be made much simpler and achieve the same effect.

* Add a delay to key lookup lock release to fix stack overflow

A tactical call_later here should fix #5723

* changelog

v1.2.0rc1

Features
--------

- Add support for opentracing. ([\#5544](https://github.com/matrix-org/synapse/issues/5544), [\#5712](https://github.com/matrix-org/synapse/issues/5712))
- Add ability to pull all locally stored events out of synapse that a particular user can see. ([\#5589](https://github.com/matrix-org/synapse/issues/5589))
- Add a basic admin command app to allow server operators to run Synapse admin commands separately from the main production instance. ([\#5597](https://github.com/matrix-org/synapse/issues/5597))
- Add `sender` and `origin_server_ts` fields to `m.replace`. ([\#5613](https://github.com/matrix-org/synapse/issues/5613))
- Add default push rule to ignore reactions. ([\#5623](https://github.com/matrix-org/synapse/issues/5623))
- Include the original event when asking for its relations. ([\#5626](https://github.com/matrix-org/synapse/issues/5626))
- Implement `session_lifetime` configuration option, after which access tokens will expire. ([\#5660](https://github.com/matrix-org/synapse/issues/5660))
- Return "This account has been deactivated" when a deactivated user tries to login. ([\#5674](https://github.com/matrix-org/synapse/issues/5674))
- Enable aggregations support by default ([\#5714](https://github.com/matrix-org/synapse/issues/5714))

Bugfixes
--------

- Fix 'utime went backwards' errors on daemonization. ([\#5609](https://github.com/matrix-org/synapse/issues/5609))
- Various minor fixes to the federation request rate limiter. ([\#5621](https://github.com/matrix-org/synapse/issues/5621))
- Forbid viewing relations on an event once it has been redacted. ([\#5629](https://github.com/matrix-org/synapse/issues/5629))
- Fix requests to the `/store_invite` endpoint of identity servers being sent in the wrong format. ([\#5638](https://github.com/matrix-org/synapse/issues/5638))
- Fix newly-registered users not being able to lookup their own profile without joining a room. ([\#5644](https://github.com/matrix-org/synapse/issues/5644))
- Fix bug in #5626 that prevented the original_event field from actually having the contents of the original event in a call to `/relations`. ([\#5654](https://github.com/matrix-org/synapse/issues/5654))
- Fix 3PID bind requests being sent to identity servers as `application/x-form-www-urlencoded` data, which is deprecated. ([\#5658](https://github.com/matrix-org/synapse/issues/5658))
- Fix some problems with authenticating redactions in recent room versions. ([\#5699](https://github.com/matrix-org/synapse/issues/5699), [\#5700](https://github.com/matrix-org/synapse/issues/5700), [\#5707](https://github.com/matrix-org/synapse/issues/5707))
- Ignore redactions of m.room.create events. ([\#5701](https://github.com/matrix-org/synapse/issues/5701))

Updates to the Docker image
---------------------------

- Base Docker image on a newer Alpine Linux version (3.8 -> 3.10). ([\#5619](https://github.com/matrix-org/synapse/issues/5619))
- Add missing space in default logging file format generated by the Docker image. ([\#5620](https://github.com/matrix-org/synapse/issues/5620))

Improved Documentation
----------------------

- Add information about nginx normalisation to reverse_proxy.rst. Contributed by @skalarproduktraum - thanks! ([\#5397](https://github.com/matrix-org/synapse/issues/5397))
- --no-pep517 should be --no-use-pep517 in the documentation to setup the development environment. ([\#5651](https://github.com/matrix-org/synapse/issues/5651))
- Improvements to Postgres setup instructions. Contributed by @Lrizika - thanks! ([\#5661](https://github.com/matrix-org/synapse/issues/5661))
- Minor tweaks to postgres documentation. ([\#5675](https://github.com/matrix-org/synapse/issues/5675))

Deprecations and Removals
-------------------------

- Remove support for the `invite_3pid_guest` configuration setting. ([\#5625](https://github.com/matrix-org/synapse/issues/5625))

Internal Changes
----------------

- Move logging code out of `synapse.util` and into `synapse.logging`. ([\#5606](https://github.com/matrix-org/synapse/issues/5606), [\#5617](https://github.com/matrix-org/synapse/issues/5617))
- Add a blacklist file to the repo to blacklist certain sytests from failing CI. ([\#5611](https://github.com/matrix-org/synapse/issues/5611))
- Make runtime errors surrounding password reset emails much clearer. ([\#5616](https://github.com/matrix-org/synapse/issues/5616))
- Remove dead code for persiting outgoing federation transactions. ([\#5622](https://github.com/matrix-org/synapse/issues/5622))
- Add `lint.sh` to the scripts-dev folder which will run all linting steps required by CI. ([\#5627](https://github.com/matrix-org/synapse/issues/5627))
- Move RegistrationHandler.get_or_create_user to test code. ([\#5628](https://github.com/matrix-org/synapse/issues/5628))
- Add some more common python virtual-environment paths to the black exclusion list. ([\#5630](https://github.com/matrix-org/synapse/issues/5630))
- Some counter metrics exposed over Prometheus have been renamed, with the old names preserved for backwards compatibility and deprecated. See `docs/metrics-howto.rst` for details. ([\#5636](https://github.com/matrix-org/synapse/issues/5636))
- Unblacklist some user_directory sytests. ([\#5637](https://github.com/matrix-org/synapse/issues/5637))
- Factor out some redundant code in the login implementation. ([\#5639](https://github.com/matrix-org/synapse/issues/5639))
- Update ModuleApi to avoid register(generate_token=True). ([\#5640](https://github.com/matrix-org/synapse/issues/5640))
- Remove access-token support from `RegistrationHandler.register`, and rename it. ([\#5641](https://github.com/matrix-org/synapse/issues/5641))
- Remove access-token support from `RegistrationStore.register`, and rename it. ([\#5642](https://github.com/matrix-org/synapse/issues/5642))
- Improve logging for auto-join when a new user is created. ([\#5643](https://github.com/matrix-org/synapse/issues/5643))
- Remove unused and unnecessary check for FederationDeniedError in _exception_to_failure. ([\#5645](https://github.com/matrix-org/synapse/issues/5645))
- Fix a small typo in a code comment. ([\#5655](https://github.com/matrix-org/synapse/issues/5655))
- Clean up exception handling around client access tokens. ([\#5656](https://github.com/matrix-org/synapse/issues/5656))
- Add a mechanism for per-test homeserver configuration in the unit tests. ([\#5657](https://github.com/matrix-org/synapse/issues/5657))
- Inline issue_access_token. ([\#5659](https://github.com/matrix-org/synapse/issues/5659))
- Update the sytest BuildKite configuration to checkout Synapse in `/src`. ([\#5664](https://github.com/matrix-org/synapse/issues/5664))
- Add a `docker` type to the towncrier configuration. ([\#5673](https://github.com/matrix-org/synapse/issues/5673))
- Convert `synapse.federation.transport.server` to `async`. Might improve some stack traces. ([\#5689](https://github.com/matrix-org/synapse/issues/5689))
- Documentation for opentracing. ([\#5703](https://github.com/matrix-org/synapse/issues/5703))

* Remove deprecated 'verbose' cli arg

* Create 5725.bugfix

* Opentracing survival guide

* Update decorator names in doc

* Doc cleanup

These are all alterations as a result of comments in #5703, it
includes mostly typos and clarifications. The most interesting
changes are:

- Split developer and user docs into two sections
- Add a high level description of OpenTracing

* newsfile

* Move contributer specific info to docstring.

* Sample config.

* Trailing whitespace.

* Update 5703.misc

* Apply suggestions from code review

Mostly just rewording parts of the docs for clarity.

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

This reverts commit dc7cf812.

A tactical call_later here should fix #5723

There's an awful lot of deferreds and dictionaries flying around here. The
whole thing can be made much simpler and achieve the same effect.

Use upsert when updating destination retry interval

Delegate to cached version when using get_filtered_current_state_ids

Add membership column to current_state_events table

* Don't accept opentracing data from clients.

* newsfile

Its a bit disingenuousto give LoggingTransaction lists to append
callbacks to if we're not going to run the callbacks.

add rel attribute as a precaution against reverse tabnabbing in future

A few fixes and removal of duplicated stuff, but mostly a bunch of the words on the config file.

In the case where it gets called with `StateFilter.all()`

Clean up config settings and dead code.

This is mostly about cleaning up the config format, to bring it into line with our conventions. In particular:
 * There should be a blank line after `## Section ##' headings
 * There should be a blank line between each config setting
 * There should be a `#`-only line between a comment and the setting it describes
 * We don't really do the `#  #` style commenting-out of whole sections if we can help it
 * rename `tracer_enabled` to `enabled`

While we're here, do more config parsing upfront, which makes it easier to use
later on.

Also removes redundant code from LogContextScopeManager.

Also changes the changelog fragment to a `feature` - it's exciting!

Fixes #5594

Forbid viewing relations on an event once it has been redacted.

It turns out that doing a join is surprisingly expensive for the DB to
do when room_membership table is larger than the disk cache.

* Convert BaseFederationServlet._wrap to async

Empirically, this fixes some lost stacktraces. It should be safe because the
wrapped function is called from JsonResource._async_render, which is already
async.

* Convert the rest of synapse.federation.transport.server to async

We may as well do the whole file while we're here.

* changelog

* flake8

This is basically a contrived way of adding a `Recommends` on `libpq5`, to fix #5653.

The way this is supposed to happen in debhelper is to run
`dh_shlibdeps`, which in turn runs `dpkg-shlibdeps`, which spits things out
into `debian/<package>.substvars` whence they can later be included by
`control`.

Previously, we had disabled `dh_shlibdeps`, mostly because `dpkg-shlibdeps`
gets confused about PIL's interdependent objects, but that's not really the
right thing to do and there is another way to work around that.

Since we don't always use postgres, we don't necessarily want a hard Depends on
libpq5, so I've actually ended up adding an explicit invocation of
`dpkg-shlibdeps` for `psycopg2`.

I've also updated the build-depends list for the package, which was missing a
couple of entries.

We can now use `_get_events_from_cache_or_db` rather than going right back to
the database, which means that (a) we can benefit from caching, and (b) it
opens the way forward to more extensive checks on the original event.

We now always require the original event to exist before we will serve up a
redaction.