Synapse: Matrix homeserver written in Python/Twisted + Rust https://element-hq.github.io/synapse
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Filename Latest commit message Latest commit date
Olivier 'reivilibre 7773f05596
Use sharded tokens in MSC4354: Sticky Events sync and sliding sync, preventing events appearing in multiple sync responses. (#20186)
Fixes: #19661
Part of: MSC4354

First introduced some helpers for querying a sharded stream, which were moved to
https://github.com/element-hq/synapse/pull/20108.

- SQL builder for 'give me rows between two sharded tokens'
- a function to return the 'new' from_token after a limited read


Then make the sticky events portions of both oldschool and sliding sync use
sharded tokens.

This prevents a 'torn sync' problem where, because the events and sticky
events streams are both sharded with the same writers:

1. persisting a sticky event leads to an event row and a `sticky_events`
row being created for event `e` (on writer `W`).
2. Suppose another writer is still persisting, so the position of the
stream for writer W advances, but the global
['linear'](https://element-hq.github.io/synapse/latest/development/synapse_architecture/streams.html?highlight=%E2%80%9Clinear%E2%80%9D#current-stream-id)
(I have been calling this 'baseline') position does not advance yet.
3. sync is sharding-aware for the regular events stream, so `e` appears
as a real-time timeline event, thus coming down sync
4. since sticky events were not sharding-aware, `e` is not detected as a
sticky event in this sync response. The sticky event position doesn't
advance in the sync token, either.
5. (assume the position advances because other writers have finished
writing and so the 'linear' position advances for the sticky events
stream)
6. the client then syncs again, using the new sync token. This time, `e`
appears in the sticky event section.

If we make sticky events sharding-aware in sync, then `e` would appear
for consideration in both the timeline section **and** the sticky event
section in the first sync.
It then gets deduplicated out of the sticky section since it is
appearing in the timeline section in the same sync.

---------

Signed-off-by: Olivier 'reivilibre <oliverw@matrix.org>
Co-authored-by: Eric Eastwood <erice@element.io>
2026-10-05 12:40:55 +01:00
.ci Schema diff CI: Fix hanging when Rust module changes (#20129) 2026-08-20 16:43:24 +01:00
.github Use beautifulsoup4 instead of lxml for URL previews (#19301) 2026-10-02 15:46:34 +01:00
changelog.d Use sharded tokens in MSC4354: Sticky Events sync and sliding sync, preventing events appearing in multiple sync responses. (#20186) 2026-10-05 12:40:55 +01:00
complement Bump the all-go-dependencies group in /complement with 2 updates (#20271) 2026-09-25 11:40:11 +00:00
contrib Document how to capture a JSON snapshot of a Grafana dashboard (#20048) 2026-08-05 11:11:30 -05:00
debian 1.162.0 2026-09-29 11:15:31 -05:00
demo Profile endpoint rate limit (#20218) 2026-09-18 12:00:45 +01:00
docker Docker: support workers for MSC4140 single lookup (#20262) 2026-09-24 16:41:59 +01:00
docs Use beautifulsoup4 instead of lxml for URL previews (#19301) 2026-10-02 15:46:34 +01:00
rust Advertise support for Matrix v1.15 (#20286) 2026-09-30 16:17:12 +01:00
schema Reject limit_profile_requests_to_users_who_share_rooms without require_auth_for_profile_requests (#20231) 2026-09-23 16:33:17 +00:00
scripts-dev Update release script to check more often for actions being completed (every 1m) (#20093) 2026-08-12 11:54:53 -05:00
stubs Bump Twisted in poetry.lock from 25.5.0 to 26.4.0 (#20259) 2026-09-29 17:50:55 +00:00
synapse Use sharded tokens in MSC4354: Sticky Events sync and sliding sync, preventing events appearing in multiple sync responses. (#20186) 2026-10-05 12:40:55 +01:00
synmark Port Clock functions to use Duration class (#19229) 2025-12-01 13:55:06 +00:00
tests Use sharded tokens in MSC4354: Sticky Events sync and sliding sync, preventing events appearing in multiple sync responses. (#20186) 2026-10-05 12:40:55 +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 Align comments in .dockerignore with synapse-private pro branch (#20224) 2026-09-17 10:09:17 -05:00
.editorconfig Apply correct editorconfig to .pyi files (#14526) 2022-11-22 18:33:28 +00:00
.git-blame-ignore-revs Ignore Python language refactors (.git-blame-ignore-revs) (#19150) 2025-11-10 22:34:30 +00:00
.gitignore add before and after filter to redact user method (/_synapse/admin/v1/user/$user_id/redact) (#19802) 2026-07-01 17:28:22 +01:00
.rustfmt.toml Prevent dirty Cargo.lock changes from install (#18693) 2025-07-18 10:28:10 -05:00
AUTHORS.rst Automatically delete empty groups/communities (#6453) 2019-12-16 12:12:40 +00:00
book.toml Bump mdbook from 0.4.17 -> 0.5.2 and remove custom table-of-contents plugin (#19356) 2026-01-07 18:46:03 +00:00
build_rust.py Drop Python 3.9, bump tests/builds to Python 3.10 (#19099) 2025-10-29 12:15:00 -05:00
Cargo.lock Bump the all-rust-dependencies group across 1 directory with 6 updates (#20268) 2026-09-29 15:47:19 +01:00
Cargo.toml Fix building rust with nightly (#15906) 2023-07-10 16:24:04 +01:00
CHANGES.md 1.162.0 2026-09-29 11:15:31 -05:00
CONTRIBUTING.md Update the contributing guide after reliecensing (#16772) 2024-01-03 11:31:03 +00:00
flake.lock Fix nix flake 2024-11-20 15:01:56 +00:00
flake.nix Use beautifulsoup4 instead of lxml for URL previews (#19301) 2026-10-02 15:46:34 +01:00
INSTALL.md Update book location 2023-12-13 16:15:22 +00:00
LICENSE-AGPL-3.0 make dual licensing explicit (#18134) 2025-02-05 13:40:10 +00:00
LICENSE-COMMERCIAL make dual licensing explicit (#18134) 2025-02-05 13:40:10 +00:00
mypy.ini Migrate dev dependencies to PEP 735 dependency groups (#19490) 2026-03-17 14:45:28 +00:00
poetry.lock Use beautifulsoup4 instead of lxml for URL previews (#19301) 2026-10-02 15:46:34 +01:00
pyproject.toml Use beautifulsoup4 instead of lxml for URL previews (#19301) 2026-10-02 15:46:34 +01:00
README.rst Fix a few readme links regarding ESS (#19070) 2026-09-24 09:58:57 +00:00
sytest-blacklist Use full GitHub links instead of bare issue numbers. (#16637) 2023-11-15 08:02:11 -05:00
tox.ini Drop Python 3.9, bump tests/builds to Python 3.10 (#19099) 2025-10-29 12:15:00 -05:00
UPGRADE.rst Update book location 2023-12-13 16:15:22 +00:00

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.. image:: https://github.com/element-hq/synapse/raw/develop/docs/element_logo_white_bg.svg
   :height: 60px

**Element Synapse - Matrix homeserver implementation**

|support| |development| |documentation| |license| |pypi| |python|

Synapse is an open source `Matrix <https://matrix.org>`__ homeserver
implementation, written and maintained by `Element <https://element.io>`_.
`Matrix <https://github.com/matrix-org>`__ is the open standard for secure and
interoperable real-time communications. You can directly run and manage the
source code in this repository, available under an AGPL license (or
alternatively under a commercial license from Element).

There is no support provided by Element unless you have a subscription from
Element.

🚀 Getting started
==================

This component is developed and maintained by `Element <https://element.io>`_.
It gets shipped as part of the **Element Server Suite (ESS)** which provides the
official means of deployment.

ESS is a Matrix distribution from Element with focus on quality and ease of use.
It ships a full Matrix stack tailored to the respective use case.

There are three editions of ESS:

- `ESS Community <https://github.com/element-hq/ess-helm>`_ - the free Matrix
  distribution from Element tailored to small-/mid-scale, non-commercial
  community use cases
- `ESS Pro <https://element.io/server-suite>`_ - the commercial Matrix
  distribution from Element for professional use
- `ESS TI-M <https://element.io/server-suite/ti-messenger>`_ - a special version
  of ESS Pro focused on the requirements of TI-Messenger Pro and ePA as
  specified by the German National Digital Health Agency Gematik


🛠️ Standalone installation and configuration
============================================

The Synapse documentation describes `options for installing Synapse standalone
<https://element-hq.github.io/synapse/latest/setup/installation.html>`_. See
below for more useful documentation links.

- `Synapse configuration options <https://element-hq.github.io/synapse/latest/usage/configuration/config_documentation.html>`_
- `Synapse configuration for federation <https://element-hq.github.io/synapse/latest/federate.html>`_
- `Using a reverse proxy with Synapse <https://element-hq.github.io/synapse/latest/reverse_proxy.html>`_
- `Upgrading Synapse <https://element-hq.github.io/synapse/develop/upgrade.html>`_


🎯 Troubleshooting and support
==============================

🚀 Professional support
-----------------------

Enterprise quality support for Synapse including SLAs is available as part of an
`Element Server Suite (ESS) <https://element.io/pricing>`_ subscription.

If you are an existing ESS subscriber then you can raise a `support request <https://customer.element.io/support>`_
and access the `Element product documentation <https://docs.element.io>`_.

🤝 Community support
--------------------

The `Admin FAQ <https://element-hq.github.io/synapse/latest/usage/administration/admin_faq.html>`_
includes tips on dealing with some common problems. For more details, see
`Synapse's wider documentation <https://element-hq.github.io/synapse/latest/>`_.

For additional support installing or managing Synapse, please ask in the community
support room |room|_ (from a matrix.org account if necessary). 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

.. |docs| replace:: ``docs``
.. _docs: docs


🛠️ Development
==============

We welcome contributions to Synapse from the community!
The best place to get started is our
`guide for contributors <https://element-hq.github.io/synapse/latest/development/contributing_guide.html>`_.
This is part of our broader `documentation <https://element-hq.github.io/synapse/latest>`_, which includes
information for Synapse developers as well as Synapse administrators.

Developers might be particularly interested in:

* `Synapse's database schema <https://element-hq.github.io/synapse/latest/development/database_schema.html>`_,
* `notes on Synapse's implementation details <https://element-hq.github.io/synapse/latest/development/internal_documentation/index.html>`_, and
* `how we use git <https://element-hq.github.io/synapse/latest/development/git.html>`_.

Alongside all that, join our developer community on Matrix:
`#synapse-dev:matrix.org <https://matrix.to/#/#synapse-dev:matrix.org>`_, featuring real humans!

Copyright and Licensing
=======================

  | Copyright 2014–2017 OpenMarket Ltd
  | Copyright 2017 Vector Creations Ltd
  | Copyright 2017–2025 New Vector Ltd
  | Copyright 2025 Element Creations Ltd

This software is dual-licensed by Element Creations Ltd (Element). It can be
used either:

(1) for free under the terms of the GNU Affero General Public License (as
    published by the Free Software Foundation, either version 3 of the License,
    or (at your option) any later version); OR

(2) under the terms of a paid-for Element Commercial License agreement between
    you and Element (the terms of which may vary depending on what you and
    Element have agreed to).

Unless required by applicable law or agreed to in writing, software distributed
under the Licenses is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
CONDITIONS OF ANY KIND, either express or implied. See the Licenses for the
specific language governing permissions and limitations under the Licenses.

Please contact `licensing@element.io <mailto:licensing@element.io>`_ to purchase
an Element commercial license for this software.


.. |support| image:: https://img.shields.io/badge/matrix-community%20support-success
  :alt: (get community support in #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

.. |documentation| image:: https://img.shields.io/badge/documentation-%E2%9C%93-success
  :alt: (Rendered documentation on GitHub Pages)
  :target: https://element-hq.github.io/synapse/latest/

.. |license| image:: https://img.shields.io/github/license/element-hq/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