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diff --git a/docs/workers.rst b/docs/workers.rst new file mode 100644 index 0000000000..4eb05b0e59 --- /dev/null +++ b/docs/workers.rst @@ -0,0 +1,97 @@ +Scaling synapse via workers +--------------------------- + +Synapse has experimental support for splitting out functionality into +multiple separate python processes, helping greatly with scalability. These +processes are called 'workers', and are (eventually) intended to scale +horizontally independently. + +All processes continue to share the same database instance, and as such, workers +only work with postgres based synapse deployments (sharing a single sqlite +across multiple processes is a recipe for disaster, plus you should be using +postgres anyway if you care about scalability). + +The workers communicate with the master synapse process via a synapse-specific +HTTP protocol called 'replication' - analogous to MySQL or Postgres style +database replication; feeding a stream of relevant data to the workers so they +can be kept in sync with the main synapse process and database state. + +To enable workers, you need to add a replication listener to the master synapse, e.g.:: + + listeners: + - port: 9092 + bind_address: '127.0.0.1' + type: http + tls: false + x_forwarded: false + resources: + - names: [replication] + compress: false + +Under **no circumstances** should this replication API listener be exposed to the +public internet; it currently implements no authentication whatsoever and is +unencrypted HTTP. + +You then create a set of configs for the various worker processes. These should be +worker configuration files should be stored in a dedicated subdirectory, to allow +synctl to manipulate them. + +The current available worker applications are: + * synapse.app.pusher - handles sending push notifications to sygnal and email + * synapse.app.synchrotron - handles /sync endpoints. can scales horizontally through multiple instances. + * synapse.app.appservice - handles output traffic to Application Services + * synapse.app.federation_reader - handles receiving federation traffic (including public_rooms API) + * synapse.app.media_repository - handles the media repository. + +Each worker configuration file inherits the configuration of the main homeserver +configuration file. You can then override configuration specific to that worker, +e.g. the HTTP listener that it provides (if any); logging configuration; etc. +You should minimise the number of overrides though to maintain a usable config. + +You must specify the type of worker application (worker_app) and the replication +endpoint that it's talking to on the main synapse process (worker_replication_url). + +For instance:: + + worker_app: synapse.app.synchrotron + + # The replication listener on the synapse to talk to. + worker_replication_url: http://127.0.0.1:9092/_synapse/replication + + worker_listeners: + - type: http + port: 8083 + resources: + - names: + - client + + worker_daemonize: True + worker_pid_file: /home/matrix/synapse/synchrotron.pid + worker_log_config: /home/matrix/synapse/config/synchrotron_log_config.yaml + +...is a full configuration for a synchrotron worker instance, which will expose a +plain HTTP /sync endpoint on port 8083 separately from the /sync endpoint provided +by the main synapse. + +Obviously you should configure your loadbalancer to route the /sync endpoint to +the synchrotron instance(s) in this instance. + +Finally, to actually run your worker-based synapse, you must pass synctl the -a +commandline option to tell it to operate on all the worker configurations found +in the given directory, e.g.:: + + synctl -a $CONFIG/workers start + +Currently one should always restart all workers when restarting or upgrading +synapse, unless you explicitly know it's safe not to. For instance, restarting +synapse without restarting all the synchrotrons may result in broken typing +notifications. + +To manipulate a specific worker, you pass the -w option to synctl:: + + synctl -w $CONFIG/workers/synchrotron.yaml restart + +All of the above is highly experimental and subject to change as Synapse evolves, +but documenting it here to help folks needing highly scalable Synapses similar +to the one running matrix.org! + |