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Eric Eastwood 684d19a11c
Add support for MSC2716 marker events (#10498)
* Make historical messages available to federated servers

Part of MSC2716: https://github.com/matrix-org/matrix-doc/pull/2716

Follow-up to https://github.com/matrix-org/synapse/pull/9247

* Debug message not available on federation

* Add base starting insertion point when no chunk ID is provided

* Fix messages from multiple senders in historical chunk

Follow-up to https://github.com/matrix-org/synapse/pull/9247

Part of MSC2716: https://github.com/matrix-org/matrix-doc/pull/2716

---

Previously, Synapse would throw a 403,
`Cannot force another user to join.`,
because we were trying to use `?user_id` from a single virtual user
which did not match with messages from other users in the chunk.

* Remove debug lines

* Messing with selecting insertion event extremeties

* Move db schema change to new version

* Add more better comments

* Make a fake requester with just what we need

See https://github.com/matrix-org/synapse/pull/10276#discussion_r660999080

* Store insertion events in table

* Make base insertion event float off on its own

See https://github.com/matrix-org/synapse/pull/10250#issuecomment-875711889

Conflicts:
	synapse/rest/client/v1/room.py

* Validate that the app service can actually control the given user

See https://github.com/matrix-org/synapse/pull/10276#issuecomment-876316455

Conflicts:
	synapse/rest/client/v1/room.py

* Add some better comments on what we're trying to check for

* Continue debugging

* Share validation logic

* Add inserted historical messages to /backfill response

* Remove debug sql queries

* Some marker event implemntation trials

* Clean up PR

* Rename insertion_event_id to just event_id

* Add some better sql comments

* More accurate description

* Add changelog

* Make it clear what MSC the change is part of

* Add more detail on which insertion event came through

* Address review and improve sql queries

* Only use event_id as unique constraint

* Fix test case where insertion event is already in the normal DAG

* Remove debug changes

* Add support for MSC2716 marker events

* Process markers when we receive it over federation

* WIP: make hs2 backfill historical messages after marker event

* hs2 to better ask for insertion event extremity

But running into the `sqlite3.IntegrityError: NOT NULL constraint failed: event_to_state_groups.state_group`
error

* Add insertion_event_extremities table

* Switch to chunk events so we can auth via power_levels

Previously, we were using `content.chunk_id` to connect one
chunk to another. But these events can be from any `sender`
and we can't tell who should be able to send historical events.
We know we only want the application service to do it but these
events have the sender of a real historical message, not the
application service user ID as the sender. Other federated homeservers
also have no indicator which senders are an application service on
the originating homeserver.

So we want to auth all of the MSC2716 events via power_levels
and have them be sent by the application service with proper
PL levels in the room.

* Switch to chunk events for federation

* Add unstable room version to support new historical PL

* Messy: Fix undefined state_group for federated historical events

```
2021-07-13 02:27:57,810 - synapse.handlers.federation - 1248 - ERROR - GET-4 - Failed to backfill from hs1 because NOT NULL constraint failed: event_to_state_groups.state_group
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/synapse/handlers/federation.py", line 1216, in try_backfill
    await self.backfill(
  File "/usr/local/lib/python3.8/site-packages/synapse/handlers/federation.py", line 1035, in backfill
    await self._auth_and_persist_event(dest, event, context, backfilled=True)
  File "/usr/local/lib/python3.8/site-packages/synapse/handlers/federation.py", line 2222, in _auth_and_persist_event
    await self._run_push_actions_and_persist_event(event, context, backfilled)
  File "/usr/local/lib/python3.8/site-packages/synapse/handlers/federation.py", line 2244, in _run_push_actions_and_persist_event
    await self.persist_events_and_notify(
  File "/usr/local/lib/python3.8/site-packages/synapse/handlers/federation.py", line 3290, in persist_events_and_notify
    events, max_stream_token = await self.storage.persistence.persist_events(
  File "/usr/local/lib/python3.8/site-packages/synapse/logging/opentracing.py", line 774, in _trace_inner
    return await func(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/persist_events.py", line 320, in persist_events
    ret_vals = await yieldable_gather_results(enqueue, partitioned.items())
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/persist_events.py", line 237, in handle_queue_loop
    ret = await self._per_item_callback(
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/persist_events.py", line 577, in _persist_event_batch
    await self.persist_events_store._persist_events_and_state_updates(
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/databases/main/events.py", line 176, in _persist_events_and_state_updates
    await self.db_pool.runInteraction(
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/database.py", line 681, in runInteraction
    result = await self.runWithConnection(
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/database.py", line 770, in runWithConnection
    return await make_deferred_yieldable(
  File "/usr/local/lib/python3.8/site-packages/twisted/python/threadpool.py", line 238, in inContext
    result = inContext.theWork()  # type: ignore[attr-defined]
  File "/usr/local/lib/python3.8/site-packages/twisted/python/threadpool.py", line 254, in <lambda>
    inContext.theWork = lambda: context.call(  # type: ignore[attr-defined]
  File "/usr/local/lib/python3.8/site-packages/twisted/python/context.py", line 118, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/usr/local/lib/python3.8/site-packages/twisted/python/context.py", line 83, in callWithContext
    return func(*args, **kw)
  File "/usr/local/lib/python3.8/site-packages/twisted/enterprise/adbapi.py", line 293, in _runWithConnection
    compat.reraise(excValue, excTraceback)
  File "/usr/local/lib/python3.8/site-packages/twisted/python/deprecate.py", line 298, in deprecatedFunction
    return function(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/twisted/python/compat.py", line 403, in reraise
    raise exception.with_traceback(traceback)
  File "/usr/local/lib/python3.8/site-packages/twisted/enterprise/adbapi.py", line 284, in _runWithConnection
    result = func(conn, *args, **kw)
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/database.py", line 765, in inner_func
    return func(db_conn, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/database.py", line 549, in new_transaction
    r = func(cursor, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/synapse/logging/utils.py", line 69, in wrapped
    return f(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/databases/main/events.py", line 385, in _persist_events_txn
    self._store_event_state_mappings_txn(txn, events_and_contexts)
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/databases/main/events.py", line 2065, in _store_event_state_mappings_txn
    self.db_pool.simple_insert_many_txn(
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/database.py", line 923, in simple_insert_many_txn
    txn.execute_batch(sql, vals)
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/database.py", line 280, in execute_batch
    self.executemany(sql, args)
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/database.py", line 300, in executemany
    self._do_execute(self.txn.executemany, sql, *args)
  File "/usr/local/lib/python3.8/site-packages/synapse/storage/database.py", line 330, in _do_execute
    return func(sql, *args)
sqlite3.IntegrityError: NOT NULL constraint failed: event_to_state_groups.state_group
```

* Revert "Messy: Fix undefined state_group for federated historical events"

This reverts commit 187ab28611546321e02770944c86f30ee2bc742a.

* Fix federated events being rejected for no state_groups

Add fix from https://github.com/matrix-org/synapse/pull/10439
until it merges.

* Adapting to experimental room version

* Some log cleanup

* Add better comments around extremity fetching code and why

* Rename to be more accurate to what the function returns

* Add changelog

* Ignore rejected events

* Use simplified upsert

* Add Erik's explanation of extra event checks

See https://github.com/matrix-org/synapse/pull/10498#discussion_r680880332

* Clarify that the depth is not directly correlated to the backwards extremity that we return

See https://github.com/matrix-org/synapse/pull/10498#discussion_r681725404

* lock only matters for sqlite

See https://github.com/matrix-org/synapse/pull/10498#discussion_r681728061

* Move new SQL changes to its own delta file

* Clean up upsert docstring

* Bump database schema version (62)
2021-08-04 12:07:57 -05:00
.buildkite Fix off-by-one-error in synapse_port_db (#9991) 2021-05-24 14:03:00 +01:00
.github Fix the tests-done github actions step, again (#10512) 2021-08-02 21:06:34 +01:00
changelog.d Add support for MSC2716 marker events (#10498) 2021-08-04 12:07:57 -05:00
contrib Fix some links in docs and contrib (#10370) 2021-07-13 11:55:48 +01:00
debian Fix debian package triggers (#10481) 2021-08-03 14:45:21 +01:00
demo Handle all new rate limits in demo scripts (#9858) 2021-04-22 17:49:42 +01:00
docker Fix deb build script to set prerelease flag correctly (#10500) 2021-08-01 10:47:36 +01:00
docs Add warnings to ip_range_blacklist usage with proxies (#10129) 2021-08-03 18:13:34 +00:00
scripts Add script for getting info about recently registered users (#10290) 2021-07-06 13:03:16 +01:00
scripts-dev Add support for MSC2716 marker events (#10498) 2021-08-04 12:07:57 -05:00
snap Added explicit Python build tools to snap requirements (#7213) 2020-04-17 17:28:00 +01:00
stubs Remove redundant "coding: utf-8" lines (#9786) 2021-04-14 15:34:27 +01:00
synapse Add support for MSC2716 marker events (#10498) 2021-08-04 12:07:57 -05:00
synmark Remove redundant "coding: utf-8" lines (#9786) 2021-04-14 15:34:27 +01:00
tests Improve event caching code (#10119) 2021-08-04 13:54:51 +01:00
.codecov.yml Disable codecov reports to GH comments. 2019-07-31 10:56:02 +01:00
.coveragerc Fix coverage in sytest and use plugins for buildkite (#5922) 2019-08-29 22:19:57 +10:00
.dockerignore Reduce the amount of stuff we send in the docker context (#5564) 2019-06-27 11:18:51 +01:00
.editorconfig Add a basic .editorconfig 2018-12-03 22:38:47 -06:00
.git-blame-ignore-revs Add a list of hashes to ignore during git blame. (#9560) 2021-03-09 07:34:55 -05:00
.gitignore Compile and render Synapse's docs into a browsable, mobile-friendly and searchable website (#10086) 2021-06-03 17:20:40 +01:00
AUTHORS.rst Automatically delete empty groups/communities (#6453) 2019-12-16 12:12:40 +00:00
book.toml Compile and render Synapse's docs into a browsable, mobile-friendly and searchable website (#10086) 2021-06-03 17:20:40 +01:00
CHANGES.md Fixup changelog 2021-08-03 12:12:50 +01:00
CONTRIBUTING.md Document Complement dev usage (#10483) 2021-07-27 19:28:23 +00:00
INSTALL.md Fix broken links in INSTALL.md (#10331) 2021-07-08 15:46:13 +01:00
LICENSE Reference Matrix Home Server 2014-08-12 15:10:52 +01:00
MANIFEST.in Compile and render Synapse's docs into a browsable, mobile-friendly and searchable website (#10086) 2021-06-03 17:20:40 +01:00
mypy.ini Add type hints and comments to event auth code. (#10393) 2021-07-14 14:13:40 +01:00
pylint.cfg Added pylint config file: ignore missing-docstring messages. 2014-10-24 10:22:09 +01:00
pyproject.toml Bump black configuration to target py36 (#9781) 2021-04-13 10:41:34 +01:00
README.rst Fix README rst 2021-07-09 11:21:41 +01:00
setup.cfg Fix (final) Bugbear violations (#9838) 2021-04-20 11:50:49 +01:00
setup.py Extend the release script to tag and create the releases. (#10496) 2021-08-03 10:23:45 +00:00
synctl Improve the error message printed by synctl when synapse fails to start. (#10059) 2021-05-27 10:35:06 +01:00
sytest-blacklist Unblacklist fixed tests (#10357) 2021-07-09 17:51:15 +01:00
test_postgresql.sh Use interpreter from $PATH instead of absolute paths in various scripts using /usr/bin/env (#9689) 2021-03-25 16:53:54 +00:00
tox.ini Run black on the scripts (#9981) 2021-05-14 11:46:35 +01:00
UPGRADE.rst Fix broken links in INSTALL.md (#10331) 2021-07-08 15:46:13 +01:00

=========================================================
Synapse |support| |development| |license| |pypi| |python|
=========================================================

.. contents::

Introduction
============

Matrix is an ambitious new ecosystem for open federated Instant Messaging and
VoIP.  The basics you need to know to get up and running are:

- Everything in Matrix happens in a room.  Rooms are distributed and do not
  exist on any single server.  Rooms can be located using convenience aliases
  like ``#matrix:matrix.org`` or ``#test:localhost:8448``.

- Matrix user IDs look like ``@matthew:matrix.org`` (although in the future
  you will normally refer to yourself and others using a third party identifier
  (3PID): email address, phone number, etc rather than manipulating Matrix user IDs)

The overall architecture is::

      client <----> homeserver <=====================> homeserver <----> client
             https://somewhere.org/_matrix      https://elsewhere.net/_matrix

``#matrix:matrix.org`` is the official support room for Matrix, and can be
accessed by any client from https://matrix.org/docs/projects/try-matrix-now.html or
via IRC bridge at irc://irc.libera.chat/matrix.

Synapse is currently in rapid development, but as of version 0.5 we believe it
is sufficiently stable to be run as an internet-facing service for real usage!

About Matrix
============

Matrix specifies a set of pragmatic RESTful HTTP JSON APIs as an open standard,
which handle:

- Creating and managing fully distributed chat rooms with no
  single points of control or failure
- Eventually-consistent cryptographically secure synchronisation of room
  state across a global open network of federated servers and services
- Sending and receiving extensible messages in a room with (optional)
  end-to-end encryption
- Inviting, joining, leaving, kicking, banning room members
- Managing user accounts (registration, login, logout)
- Using 3rd Party IDs (3PIDs) such as email addresses, phone numbers,
  Facebook accounts to authenticate, identify and discover users on Matrix.
- Placing 1:1 VoIP and Video calls

These APIs are intended to be implemented on a wide range of servers, services
and clients, letting developers build messaging and VoIP functionality on top
of the entirely open Matrix ecosystem rather than using closed or proprietary
solutions. The hope is for Matrix to act as the building blocks for a new
generation of fully open and interoperable messaging and VoIP apps for the
internet.

Synapse is a reference "homeserver" implementation of Matrix from the core
development team at matrix.org, written in Python/Twisted.  It is intended to
showcase the concept of Matrix and let folks see the spec in the context of a
codebase and let you run your own homeserver and generally help bootstrap the
ecosystem.

In Matrix, every user runs one or more Matrix clients, which connect through to
a Matrix homeserver. The homeserver stores all their personal chat history and
user account information - much as a mail client connects through to an
IMAP/SMTP server. Just like email, you can either run your own Matrix
homeserver and control and own your own communications and history or use one
hosted by someone else (e.g. matrix.org) - there is no single point of control
or mandatory service provider in Matrix, unlike WhatsApp, Facebook, Hangouts,
etc.

We'd like to invite you to join #matrix:matrix.org (via
https://matrix.org/docs/projects/try-matrix-now.html), run a homeserver, take a look
at the `Matrix spec <https://matrix.org/docs/spec>`_, and experiment with the
`APIs <https://matrix.org/docs/api>`_ and `Client SDKs
<https://matrix.org/docs/projects/try-matrix-now.html#client-sdks>`_.

Thanks for using Matrix!

Support
=======

For support installing or managing Synapse, please join |room|_ (from a matrix.org
account if necessary) and ask questions there. We do not use GitHub issues for
support requests, only for bug reports and feature requests.

.. |room| replace:: ``#synapse:matrix.org``
.. _room: https://matrix.to/#/#synapse:matrix.org


Synapse Installation
====================

.. _federation:

* For details on how to install synapse, see
  `Installation Instructions <https://matrix-org.github.io/synapse/latest/setup/installation.html>`_.
* For specific details on how to configure Synapse for federation see `docs/federate.md <docs/federate.md>`_


Connecting to Synapse from a client
===================================

The easiest way to try out your new Synapse installation is by connecting to it
from a web client.

Unless you are running a test instance of Synapse on your local machine, in
general, you will need to enable TLS support before you can successfully
connect from a client: see
`TLS certificates <https://matrix-org.github.io/synapse/latest/setup/installation.html#tls-certificates>`_.

An easy way to get started is to login or register via Element at
https://app.element.io/#/login or https://app.element.io/#/register respectively.
You will need to change the server you are logging into from ``matrix.org``
and instead specify a Homeserver URL of ``https://<server_name>:8448``
(or just ``https://<server_name>`` if you are using a reverse proxy).
If you prefer to use another client, refer to our
`client breakdown <https://matrix.org/docs/projects/clients-matrix>`_.

If all goes well you should at least be able to log in, create a room, and
start sending messages.

.. _`client-user-reg`:

Registering a new user from a client
------------------------------------

By default, registration of new users via Matrix clients is disabled. To enable
it, specify ``enable_registration: true`` in ``homeserver.yaml``. (It is then
recommended to also set up CAPTCHA - see `<docs/CAPTCHA_SETUP.md>`_.)

Once ``enable_registration`` is set to ``true``, it is possible to register a
user via a Matrix client.

Your new user name will be formed partly from the ``server_name``, and partly
from a localpart you specify when you create the account. Your name will take
the form of::

    @localpart:my.domain.name

(pronounced "at localpart on my dot domain dot name").

As when logging in, you will need to specify a "Custom server".  Specify your
desired ``localpart`` in the 'User name' box.

Security note
=============

Matrix serves raw, user-supplied data in some APIs -- specifically the `content
repository endpoints`_.

.. _content repository endpoints: https://matrix.org/docs/spec/client_server/latest.html#get-matrix-media-r0-download-servername-mediaid

Whilst we make a reasonable effort to mitigate against XSS attacks (for
instance, by using `CSP`_), a Matrix homeserver should not be hosted on a
domain hosting other web applications. This especially applies to sharing
the domain with Matrix web clients and other sensitive applications like
webmail. See
https://developer.github.com/changes/2014-04-25-user-content-security for more
information.

.. _CSP: https://github.com/matrix-org/synapse/pull/1021

Ideally, the homeserver should not simply be on a different subdomain, but on
a completely different `registered domain`_ (also known as top-level site or
eTLD+1). This is because `some attacks`_ are still possible as long as the two
applications share the same registered domain.

.. _registered domain: https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-03#section-2.3

.. _some attacks: https://en.wikipedia.org/wiki/Session_fixation#Attacks_using_cross-subdomain_cookie

To illustrate this with an example, if your Element Web or other sensitive web
application is hosted on ``A.example1.com``, you should ideally host Synapse on
``example2.com``. Some amount of protection is offered by hosting on
``B.example1.com`` instead, so this is also acceptable in some scenarios.
However, you should *not* host your Synapse on ``A.example1.com``.

Note that all of the above refers exclusively to the domain used in Synapse's
``public_baseurl`` setting. In particular, it has no bearing on the domain
mentioned in MXIDs hosted on that server.

Following this advice ensures that even if an XSS is found in Synapse, the
impact to other applications will be minimal.


Upgrading an existing Synapse
=============================

The instructions for upgrading synapse are in `the upgrade notes`_.
Please check these instructions as upgrading may require extra steps for some
versions of synapse.

.. _the upgrade notes: https://matrix-org.github.io/synapse/develop/upgrade.html

.. _reverse-proxy:

Using a reverse proxy with Synapse
==================================

It is recommended to put a reverse proxy such as
`nginx <https://nginx.org/en/docs/http/ngx_http_proxy_module.html>`_,
`Apache <https://httpd.apache.org/docs/current/mod/mod_proxy_http.html>`_,
`Caddy <https://caddyserver.com/docs/quick-starts/reverse-proxy>`_,
`HAProxy <https://www.haproxy.org/>`_ or
`relayd <https://man.openbsd.org/relayd.8>`_ in front of Synapse. One advantage of
doing so is that it means that you can expose the default https port (443) to
Matrix clients without needing to run Synapse with root privileges.

For information on configuring one, see `<docs/reverse_proxy.md>`_.

Identity Servers
================

Identity servers have the job of mapping email addresses and other 3rd Party
IDs (3PIDs) to Matrix user IDs, as well as verifying the ownership of 3PIDs
before creating that mapping.

**They are not where accounts or credentials are stored - these live on home
servers. Identity Servers are just for mapping 3rd party IDs to matrix IDs.**

This process is very security-sensitive, as there is obvious risk of spam if it
is too easy to sign up for Matrix accounts or harvest 3PID data. In the longer
term, we hope to create a decentralised system to manage it (`matrix-doc #712
<https://github.com/matrix-org/matrix-doc/issues/712>`_), but in the meantime,
the role of managing trusted identity in the Matrix ecosystem is farmed out to
a cluster of known trusted ecosystem partners, who run 'Matrix Identity
Servers' such as `Sydent <https://github.com/matrix-org/sydent>`_, whose role
is purely to authenticate and track 3PID logins and publish end-user public
keys.

You can host your own copy of Sydent, but this will prevent you reaching other
users in the Matrix ecosystem via their email address, and prevent them finding
you. We therefore recommend that you use one of the centralised identity servers
at ``https://matrix.org`` or ``https://vector.im`` for now.

To reiterate: the Identity server will only be used if you choose to associate
an email address with your account, or send an invite to another user via their
email address.


Password reset
==============

Users can reset their password through their client. Alternatively, a server admin
can reset a users password using the `admin API <docs/admin_api/user_admin_api.rst#reset-password>`_
or by directly editing the database as shown below.

First calculate the hash of the new password::

    $ ~/synapse/env/bin/hash_password
    Password:
    Confirm password:
    $2a$12$xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Then update the ``users`` table in the database::

    UPDATE users SET password_hash='$2a$12$xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'
        WHERE name='@test:test.com';


Synapse Development
===================

Join our developer community on Matrix: `#synapse-dev:matrix.org <https://matrix.to/#/#synapse-dev:matrix.org>`_

Before setting up a development environment for synapse, make sure you have the
system dependencies (such as the python header files) installed - see
`Installing from source <https://matrix-org.github.io/synapse/latest/setup/installation.html#installing-from-source>`_.

To check out a synapse for development, clone the git repo into a working
directory of your choice::

    git clone https://github.com/matrix-org/synapse.git
    cd synapse

Synapse has a number of external dependencies, that are easiest
to install using pip and a virtualenv::

    python3 -m venv ./env
    source ./env/bin/activate
    pip install -e ".[all,test]"

This will run a process of downloading and installing all the needed
dependencies into a virtual env. If any dependencies fail to install,
try installing the failing modules individually::

    pip install -e "module-name"

We recommend using the demo which starts 3 federated instances running on ports `8080` - `8082`

    ./demo/start.sh

(to stop, you can use `./demo/stop.sh`)

If you just want to start a single instance of the app and run it directly::

    # Create the homeserver.yaml config once
    python -m synapse.app.homeserver \
      --server-name my.domain.name \
      --config-path homeserver.yaml \
      --generate-config \
      --report-stats=[yes|no]

    # Start the app
    python -m synapse.app.homeserver --config-path homeserver.yaml


Running the unit tests
======================

After getting up and running, you may wish to run Synapse's unit tests to
check that everything is installed correctly::

    trial tests

This should end with a 'PASSED' result (note that exact numbers will
differ)::

    Ran 1337 tests in 716.064s

    PASSED (skips=15, successes=1322)

For more tips on running the unit tests, like running a specific test or
to see the logging output, see the `CONTRIBUTING doc <CONTRIBUTING.md#run-the-unit-tests>`_.


Running the Integration Tests
=============================

Synapse is accompanied by `SyTest <https://github.com/matrix-org/sytest>`_,
a Matrix homeserver integration testing suite, which uses HTTP requests to
access the API as a Matrix client would. It is able to run Synapse directly from
the source tree, so installation of the server is not required.

Testing with SyTest is recommended for verifying that changes related to the
Client-Server API are functioning correctly. See the `SyTest installation
instructions <https://github.com/matrix-org/sytest#installing>`_ for details.


Platform dependencies
=====================

Synapse uses a number of platform dependencies such as Python and PostgreSQL,
and aims to follow supported upstream versions. See the
`<docs/deprecation_policy.md>`_ document for more details.


Troubleshooting
===============

Need help? Join our community support room on Matrix:
`#synapse:matrix.org <https://matrix.to/#/#synapse:matrix.org>`_

Running out of File Handles
---------------------------

If synapse runs out of file handles, it typically fails badly - live-locking
at 100% CPU, and/or failing to accept new TCP connections (blocking the
connecting client).  Matrix currently can legitimately use a lot of file handles,
thanks to busy rooms like #matrix:matrix.org containing hundreds of participating
servers.  The first time a server talks in a room it will try to connect
simultaneously to all participating servers, which could exhaust the available
file descriptors between DNS queries & HTTPS sockets, especially if DNS is slow
to respond. (We need to improve the routing algorithm used to be better than
full mesh, but as of March 2019 this hasn't happened yet).

If you hit this failure mode, we recommend increasing the maximum number of
open file handles to be at least 4096 (assuming a default of 1024 or 256).
This is typically done by editing ``/etc/security/limits.conf``

Separately, Synapse may leak file handles if inbound HTTP requests get stuck
during processing - e.g. blocked behind a lock or talking to a remote server etc.
This is best diagnosed by matching up the 'Received request' and 'Processed request'
log lines and looking for any 'Processed request' lines which take more than
a few seconds to execute. Please let us know at #synapse:matrix.org if
you see this failure mode so we can help debug it, however.

Help!! Synapse is slow and eats all my RAM/CPU!
-----------------------------------------------

First, ensure you are running the latest version of Synapse, using Python 3
with a PostgreSQL database.

Synapse's architecture is quite RAM hungry currently - we deliberately
cache a lot of recent room data and metadata in RAM in order to speed up
common requests. We'll improve this in the future, but for now the easiest
way to either reduce the RAM usage (at the risk of slowing things down)
is to set the almost-undocumented ``SYNAPSE_CACHE_FACTOR`` environment
variable. The default is 0.5, which can be decreased to reduce RAM usage
in memory constrained enviroments, or increased if performance starts to
degrade.

However, degraded performance due to a low cache factor, common on
machines with slow disks, often leads to explosions in memory use due
backlogged requests. In this case, reducing the cache factor will make
things worse. Instead, try increasing it drastically. 2.0 is a good
starting value.

Using `libjemalloc <http://jemalloc.net/>`_ can also yield a significant
improvement in overall memory use, and especially in terms of giving back
RAM to the OS. To use it, the library must simply be put in the
LD_PRELOAD environment variable when launching Synapse. On Debian, this
can be done by installing the ``libjemalloc1`` package and adding this
line to ``/etc/default/matrix-synapse``::

    LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.1

This can make a significant difference on Python 2.7 - it's unclear how
much of an improvement it provides on Python 3.x.

If you're encountering high CPU use by the Synapse process itself, you
may be affected by a bug with presence tracking that leads to a
massive excess of outgoing federation requests (see `discussion
<https://github.com/matrix-org/synapse/issues/3971>`_). If metrics
indicate that your server is also issuing far more outgoing federation
requests than can be accounted for by your users' activity, this is a
likely cause. The misbehavior can be worked around by setting
the following in the Synapse config file:

.. code-block:: yaml

   presence:
       enabled: false

People can't accept room invitations from me
--------------------------------------------

The typical failure mode here is that you send an invitation to someone
to join a room or direct chat, but when they go to accept it, they get an
error (typically along the lines of "Invalid signature"). They might see
something like the following in their logs::

    2019-09-11 19:32:04,271 - synapse.federation.transport.server - 288 - WARNING - GET-11752 - authenticate_request failed: 401: Invalid signature for server <server> with key ed25519:a_EqML: Unable to verify signature for <server>

This is normally caused by a misconfiguration in your reverse-proxy. See
`<docs/reverse_proxy.md>`_ and double-check that your settings are correct.

.. |support| image:: https://img.shields.io/matrix/synapse:matrix.org?label=support&logo=matrix
  :alt: (get support on #synapse:matrix.org)
  :target: https://matrix.to/#/#synapse:matrix.org

.. |development| image:: https://img.shields.io/matrix/synapse-dev:matrix.org?label=development&logo=matrix
  :alt: (discuss development on #synapse-dev:matrix.org)
  :target: https://matrix.to/#/#synapse-dev:matrix.org

.. |license| image:: https://img.shields.io/github/license/matrix-org/synapse
  :alt: (check license in LICENSE file)
  :target: LICENSE

.. |pypi| image:: https://img.shields.io/pypi/v/matrix-synapse
  :alt: (latest version released on PyPi)
  :target: https://pypi.org/project/matrix-synapse

.. |python| image:: https://img.shields.io/pypi/pyversions/matrix-synapse
  :alt: (supported python versions)
  :target: https://pypi.org/project/matrix-synapse