210 lines
8.0 KiB
ReStructuredText
210 lines
8.0 KiB
ReStructuredText
Scaling synapse via workers
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===========================
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Synapse has experimental support for splitting out functionality into
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multiple separate python processes, helping greatly with scalability. These
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processes are called 'workers', and are (eventually) intended to scale
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horizontally independently.
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All of the below is highly experimental and subject to change as Synapse evolves,
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but documenting it here to help folks needing highly scalable Synapses similar
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to the one running matrix.org!
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All processes continue to share the same database instance, and as such, workers
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only work with postgres based synapse deployments (sharing a single sqlite
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across multiple processes is a recipe for disaster, plus you should be using
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postgres anyway if you care about scalability).
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The workers communicate with the master synapse process via a synapse-specific
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TCP protocol called 'replication' - analogous to MySQL or Postgres style
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database replication; feeding a stream of relevant data to the workers so they
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can be kept in sync with the main synapse process and database state.
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Configuration
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-------------
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To make effective use of the workers, you will need to configure an HTTP
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reverse-proxy such as nginx or haproxy, which will direct incoming requests to
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the correct worker, or to the main synapse instance. Note that this includes
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requests made to the federation port. The caveats regarding running a
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reverse-proxy on the federation port still apply (see
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https://github.com/matrix-org/synapse/blob/master/README.rst#reverse-proxying-the-federation-port).
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To enable workers, you need to add a replication listener to the master synapse, e.g.::
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listeners:
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- port: 9092
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bind_address: '127.0.0.1'
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type: replication
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Under **no circumstances** should this replication API listener be exposed to the
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public internet; it currently implements no authentication whatsoever and is
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unencrypted.
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You then create a set of configs for the various worker processes. These
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should be worker configuration files, and should be stored in a dedicated
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subdirectory, to allow synctl to manipulate them.
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Each worker configuration file inherits the configuration of the main homeserver
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configuration file. You can then override configuration specific to that worker,
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e.g. the HTTP listener that it provides (if any); logging configuration; etc.
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You should minimise the number of overrides though to maintain a usable config.
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You must specify the type of worker application (``worker_app``). The currently
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available worker applications are listed below. You must also specify the
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replication endpoint that it's talking to on the main synapse process
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(``worker_replication_host`` and ``worker_replication_port``).
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For instance::
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worker_app: synapse.app.synchrotron
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# The replication listener on the synapse to talk to.
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worker_replication_host: 127.0.0.1
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worker_replication_port: 9092
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worker_listeners:
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- type: http
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port: 8083
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resources:
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- names:
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- client
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worker_daemonize: True
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worker_pid_file: /home/matrix/synapse/synchrotron.pid
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worker_log_config: /home/matrix/synapse/config/synchrotron_log_config.yaml
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...is a full configuration for a synchrotron worker instance, which will expose a
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plain HTTP ``/sync`` endpoint on port 8083 separately from the ``/sync`` endpoint provided
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by the main synapse.
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Obviously you should configure your reverse-proxy to route the relevant
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endpoints to the worker (``localhost:8083`` in the above example).
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Finally, to actually run your worker-based synapse, you must pass synctl the -a
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commandline option to tell it to operate on all the worker configurations found
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in the given directory, e.g.::
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synctl -a $CONFIG/workers start
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Currently one should always restart all workers when restarting or upgrading
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synapse, unless you explicitly know it's safe not to. For instance, restarting
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synapse without restarting all the synchrotrons may result in broken typing
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notifications.
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To manipulate a specific worker, you pass the -w option to synctl::
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synctl -w $CONFIG/workers/synchrotron.yaml restart
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Available worker applications
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-----------------------------
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``synapse.app.pusher``
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~~~~~~~~~~~~~~~~~~~~~~
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Handles sending push notifications to sygnal and email. Doesn't handle any
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REST endpoints itself, but you should set ``start_pushers: False`` in the
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shared configuration file to stop the main synapse sending these notifications.
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Note this worker cannot be load-balanced: only one instance should be active.
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``synapse.app.synchrotron``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The synchrotron handles ``sync`` requests from clients. In particular, it can
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handle REST endpoints matching the following regular expressions::
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^/_matrix/client/(v2_alpha|r0)/sync$
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^/_matrix/client/(api/v1|v2_alpha|r0)/events$
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^/_matrix/client/(api/v1|r0)/initialSync$
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^/_matrix/client/(api/v1|r0)/rooms/[^/]+/initialSync$
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The above endpoints should all be routed to the synchrotron worker by the
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reverse-proxy configuration.
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It is possible to run multiple instances of the synchrotron to scale
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horizontally. In this case the reverse-proxy should be configured to
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load-balance across the instances, though it will be more efficient if all
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requests from a particular user are routed to a single instance. Extracting
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a userid from the access token is currently left as an exercise for the reader.
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``synapse.app.appservice``
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Handles sending output traffic to Application Services. Doesn't handle any
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REST endpoints itself, but you should set ``notify_appservices: False`` in the
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shared configuration file to stop the main synapse sending these notifications.
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Note this worker cannot be load-balanced: only one instance should be active.
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``synapse.app.federation_reader``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Handles a subset of federation endpoints. In particular, it can handle REST
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endpoints matching the following regular expressions::
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^/_matrix/federation/v1/event/
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^/_matrix/federation/v1/state/
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^/_matrix/federation/v1/state_ids/
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^/_matrix/federation/v1/backfill/
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^/_matrix/federation/v1/get_missing_events/
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^/_matrix/federation/v1/publicRooms
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The above endpoints should all be routed to the federation_reader worker by the
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reverse-proxy configuration.
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``synapse.app.federation_sender``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Handles sending federation traffic to other servers. Doesn't handle any
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REST endpoints itself, but you should set ``send_federation: False`` in the
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shared configuration file to stop the main synapse sending this traffic.
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Note this worker cannot be load-balanced: only one instance should be active.
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``synapse.app.media_repository``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Handles the media repository. It can handle all endpoints starting with::
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/_matrix/media/
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You should also set ``enable_media_repo: False`` in the shared configuration
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file to stop the main synapse running background jobs related to managing the
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media repository.
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Note this worker cannot be load-balanced: only one instance should be active.
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``synapse.app.client_reader``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Handles client API endpoints. It can handle REST endpoints matching the
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following regular expressions::
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^/_matrix/client/(api/v1|r0|unstable)/publicRooms$
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``synapse.app.user_dir``
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~~~~~~~~~~~~~~~~~~~~~~~~
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Handles searches in the user directory. It can handle REST endpoints matching
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the following regular expressions::
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^/_matrix/client/(api/v1|r0|unstable)/user_directory/search$
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``synapse.app.frontend_proxy``
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Proxies some frequently-requested client endpoints to add caching and remove
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load from the main synapse. It can handle REST endpoints matching the following
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regular expressions::
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^/_matrix/client/(api/v1|r0|unstable)/keys/upload
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It will proxy any requests it cannot handle to the main synapse instance. It
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must therefore be configured with the location of the main instance, via
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the ``worker_main_http_uri`` setting in the frontend_proxy worker configuration
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file. For example::
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worker_main_http_uri: http://127.0.0.1:8008
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