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Olivier 'reivilibre
110f548f64
Got paged today for this. The sliding sync worker in question had loads of deadlocks in the logs. I restarted it and it got unwedged, but we should have a more robust defence, which this PR proposes. ``` psycopg2.errors.DeadlockDetected: deadlock detected DETAIL: Process 257324 waits for ShareLock on transaction 688227036; blocked by process 254908. Process 254908 waits for ShareLock on transaction 688222971; blocked by process 256179. Process 256179 waits for ExclusiveLock on tuple (302352,92) of relation 2962200779 of database 16403; blocked by process 257213. Process 257213 waits for ShareLock on transaction 688225005; blocked by process 254905. Process 254905 waits for ShareLock on transaction 688228814; blocked by process 257324. HINT: See server log for query details. CONTEXT: while inserting index tuple (183070,103) in relation "sliding_sync_connection_lazy_members" ``` I wonder if an unfortunate side effect is that these repeated attempts leave a lot of dead tuples on the table, which would then harm the performance of the next attempt to insert the tuples, I suspect making it more likely that they will deadlock again (?). --- By acquring a `FOR NO KEY UPDATE` lock upfront before beginning work, we can ensure that one of the transactions gets queued behind the other one, meaning the first one can succeed unimpeded. `FOR NO KEY UPDATE` blocks other `FOR NO KEY UPDATE` locks and is the weakest lock level that blocks itself. --------- Signed-off-by: Olivier 'reivilibre <oliverw@matrix.org>
.. 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://ems.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! 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