398 lines
15 KiB
Markdown
398 lines
15 KiB
Markdown
# Scaling synapse via workers
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For small instances it recommended to run Synapse in monolith mode (the
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default). For larger instances where performance is a concern it can be helpful
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to split out functionality into multiple separate python processes. 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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Synapse's worker support is under active development and subject to change as
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we attempt to rapidly scale ever larger Synapse instances. However we are
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documenting it here to help admins needing a highly scalable Synapse instance
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similar to the one running `matrix.org`.
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All processes continue to share the same database instance, and as such,
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workers only work with PostgreSQL-based Synapse deployments. SQLite should only
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be used for demo purposes and any admin considering workers should already be
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running PostgreSQL.
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## Master/worker communication
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The workers communicate with the master process via a Synapse-specific protocol
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called 'replication' (analogous to MySQL- or Postgres-style database
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replication) which feeds a stream of relevant data from the master to the
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workers so they can be kept in sync with the master process and database state.
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Additionally, workers may make HTTP requests to the master, to send information
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in the other direction. Typically this is used for operations which need to
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wait for a reply - such as sending an event.
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## Configuration
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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. See [reverse_proxy.md](reverse_proxy.md)
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for information on setting up a reverse proxy.
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To enable workers, you need to add *two* replication listeners to the
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main Synapse configuration file (`homeserver.yaml`). For example:
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```yaml
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listeners:
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# The TCP replication port
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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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# The HTTP replication port
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- port: 9093
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bind_address: '127.0.0.1'
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type: http
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resources:
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- names: [replication]
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```
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Under **no circumstances** should these replication API listeners be exposed to
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the public internet; they have no authentication and are unencrypted.
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You should then create a set of configs for the various worker processes. Each
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worker configuration file inherits the configuration of the main homeserver
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configuration file. You can then override configuration specific to that
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worker, e.g. the HTTP listener that it provides (if any); logging
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configuration; etc. You should minimise the number of overrides though to
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maintain a usable config.
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In the config file for each worker, you must specify the type of worker
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application (`worker_app`). The currently available worker applications are
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listed below. You must also specify the replication endpoints that it should
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talk to on the main synapse process. `worker_replication_host` should specify
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the host of the main synapse, `worker_replication_port` should point to the TCP
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replication listener port and `worker_replication_http_port` should point to
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the HTTP replication port.
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For example:
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```yaml
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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_replication_http_port: 9093
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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_log_config: /home/matrix/synapse/config/synchrotron_log_config.yaml
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```
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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, you need to start your worker processes. This can be done with either
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`synctl` or your distribution's preferred service manager such as `systemd`. We
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recommend the use of `systemd` where available: for information on setting up
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`systemd` to start synapse workers, see
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[systemd-with-workers](systemd-with-workers). To use `synctl`, see below.
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### **Experimental** support for replication over redis
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As of Synapse v1.13.0, it is possible to configure Synapse to send replication
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via a [Redis pub/sub channel](https://redis.io/topics/pubsub). This is an
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alternative to direct TCP connections to the master: rather than all the
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workers connecting to the master, all the workers and the master connect to
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Redis, which relays replication commands between processes. This can give a
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significant cpu saving on the master and will be a prerequisite for upcoming
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performance improvements.
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Note that this support is currently experimental; you may experience lost
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messages and similar problems! It is strongly recommended that admins setting
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up workers for the first time use direct TCP replication as above.
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To configure Synapse to use Redis:
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1. Install Redis following the normal procedure for your distribution - for
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example, on Debian, `apt install redis-server`. (It is safe to use an
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existing Redis deployment if you have one: we use a pub/sub stream named
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according to the `server_name` of your synapse server.)
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2. Check Redis is running and accessible: you should be able to `echo PING | nc -q1
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localhost 6379` and get a response of `+PONG`.
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3. Install the python prerequisites. If you installed synapse into a
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virtualenv, this can be done with:
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```sh
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pip install matrix-synapse[redis]
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```
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The debian packages from matrix.org already include the required
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dependencies.
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4. Add config to the shared configuration (`homeserver.yaml`):
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```yaml
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redis:
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enabled: true
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```
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Optional parameters which can go alongside `enabled` are `host`, `port`,
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`password`. Normally none of these are required.
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5. Restart master and all workers.
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Once redis replication is in use, `worker_replication_port` is redundant and
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can be removed from the worker configuration files. Similarly, the
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configuration for the `listener` for the TCP replication port can be removed
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from the main configuration file. Note that the HTTP replication port is
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still required.
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### Using synctl
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If you want to use `synctl` to manage your synapse processes, you will need to
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create an an additional configuration file for the master synapse process. That
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configuration should look like this:
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```yaml
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worker_app: synapse.app.homeserver
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```
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Additionally, each worker app must be configured with the name of a "pid file",
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to which it will write its process ID when it starts. For example, for a
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synchrotron, you might write:
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```yaml
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worker_pid_file: /home/matrix/synapse/synchrotron.pid
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```
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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 $CONFIG/workers/synchrotron.yaml restart
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## Available worker applications
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### `synapse.app.pusher`
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Handles sending push notifications to sygnal and email. Doesn't handle any
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REST endpoints itself, but you should set `start_pushers: False` in the
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shared configuration file to stop the main synapse sending these notifications.
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Note this worker cannot be load-balanced: only one instance should be active.
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### `synapse.app.synchrotron`
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The synchrotron handles `sync` requests from clients. In particular, it can
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handle REST endpoints matching the following regular expressions:
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^/_matrix/client/(v2_alpha|r0)/sync$
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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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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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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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^/_matrix/federation/v1/query/
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^/_matrix/federation/v1/make_join/
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^/_matrix/federation/v1/make_leave/
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^/_matrix/federation/v1/send_join/
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^/_matrix/federation/v2/send_join/
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^/_matrix/federation/v1/send_leave/
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^/_matrix/federation/v2/send_leave/
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^/_matrix/federation/v1/invite/
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^/_matrix/federation/v2/invite/
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^/_matrix/federation/v1/query_auth/
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^/_matrix/federation/v1/event_auth/
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^/_matrix/federation/v1/exchange_third_party_invite/
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^/_matrix/federation/v1/user/devices/
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^/_matrix/federation/v1/send/
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^/_matrix/federation/v1/get_groups_publicised$
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^/_matrix/key/v2/query
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Additionally, the following REST endpoints can be handled for GET requests:
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^/_matrix/federation/v1/groups/
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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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The `^/_matrix/federation/v1/send/` endpoint must only be handled by a single
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instance.
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Note that `federation` must be added to the listener resources in the worker config:
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```yaml
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worker_app: synapse.app.federation_reader
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...
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worker_listeners:
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- type: http
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port: <port>
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resources:
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- names:
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- federation
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```
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### `synapse.app.federation_sender`
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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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Handles the media repository. It can handle all endpoints starting with:
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/_matrix/media/
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... and the following regular expressions matching media-specific administration APIs:
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^/_synapse/admin/v1/purge_media_cache$
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^/_synapse/admin/v1/room/.*/media.*$
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^/_synapse/admin/v1/user/.*/media.*$
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^/_synapse/admin/v1/media/.*$
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^/_synapse/admin/v1/quarantine_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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In the `media_repository` worker configuration file, configure the http listener to
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expose the `media` resource. For example:
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```yaml
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worker_listeners:
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- type: http
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port: 8085
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resources:
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- names:
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- media
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```
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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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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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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/joined_members$
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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/context/.*$
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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/members$
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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/state$
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^/_matrix/client/(api/v1|r0|unstable)/login$
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^/_matrix/client/(api/v1|r0|unstable)/account/3pid$
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^/_matrix/client/(api/v1|r0|unstable)/keys/query$
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^/_matrix/client/(api/v1|r0|unstable)/keys/changes$
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^/_matrix/client/versions$
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^/_matrix/client/(api/v1|r0|unstable)/voip/turnServer$
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^/_matrix/client/(api/v1|r0|unstable)/joined_groups$
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^/_matrix/client/(api/v1|r0|unstable)/publicised_groups$
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^/_matrix/client/(api/v1|r0|unstable)/publicised_groups/
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Additionally, the following REST endpoints can be handled for GET requests:
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^/_matrix/client/(api/v1|r0|unstable)/pushrules/.*$
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^/_matrix/client/(api/v1|r0|unstable)/groups/.*$
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^/_matrix/client/(api/v1|r0|unstable)/user/[^/]*/account_data/
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^/_matrix/client/(api/v1|r0|unstable)/user/[^/]*/rooms/[^/]*/account_data/
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Additionally, the following REST endpoints can be handled, but all requests must
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be routed to the same instance:
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^/_matrix/client/(r0|unstable)/register$
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^/_matrix/client/(r0|unstable)/auth/.*/fallback/web$
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Pagination requests can also be handled, but all requests with the same path
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room must be routed to the same instance. Additionally, care must be taken to
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ensure that the purge history admin API is not used while pagination requests
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for the room are in flight:
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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/messages$
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### `synapse.app.user_dir`
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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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When using this worker you must also set `update_user_directory: False` in the
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shared configuration file to stop the main synapse running background
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jobs related to updating the user directory.
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### `synapse.app.frontend_proxy`
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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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If `use_presence` is False in the homeserver config, it can also handle REST
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endpoints matching the following regular expressions:
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^/_matrix/client/(api/v1|r0|unstable)/presence/[^/]+/status
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This "stub" presence handler will pass through `GET` request but make the
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`PUT` effectively a no-op.
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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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### `synapse.app.event_creator`
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Handles some event creation. It can handle REST endpoints matching:
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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/send
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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/state/
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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/(join|invite|leave|ban|unban|kick)$
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^/_matrix/client/(api/v1|r0|unstable)/join/
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^/_matrix/client/(api/v1|r0|unstable)/profile/
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It will create events locally and then send them on to the main synapse
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instance to be persisted and handled.
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