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549 lines
21 KiB
Markdown
549 lines
21 KiB
Markdown
# Scaling synapse via workers
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For small instances it recommended to run Synapse in the default monolith mode.
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For larger instances where performance is a concern it can be helpful to split
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out functionality into multiple separate python processes. These processes are
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called 'workers', and are (eventually) intended to scale horizontally
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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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See also [Matrix.org blog post](https://matrix.org/blog/2020/11/03/how-we-fixed-synapses-scalability)
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for a higher level overview.
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## Main process/worker communication
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The processes communicate with each other via a Synapse-specific protocol called
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'replication' (analogous to MySQL- or Postgres-style database replication) which
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feeds streams of newly written data between processes so they can be kept in
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sync with the database state.
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When configured to do so, Synapse uses a
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[Redis pub/sub channel](https://redis.io/topics/pubsub) to send the replication
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stream between all configured Synapse processes. Additionally, processes may
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make HTTP requests to each other, primarily for operations which need to wait
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for a reply ─ such as sending an event.
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Redis support was added in v1.13.0 with it becoming the recommended method in
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v1.18.0. It replaced the old direct TCP connections (which is deprecated as of
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v1.18.0) to the main process. With Redis, rather than all the workers connecting
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to the main process, all the workers and the main process connect to Redis,
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which relays replication commands between processes. This can give a significant
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cpu saving on the main process and will be a prerequisite for upcoming
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performance improvements.
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If Redis support is enabled Synapse will use it as a shared cache, as well as a
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pub/sub mechanism.
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See the [Architectural diagram](#architectural-diagram) section at the end for
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a visualisation of what this looks like.
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## Setting up workers
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A Redis server is required to manage the communication between the processes.
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The Redis server should be installed following the normal procedure for your
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distribution (e.g. `apt install redis-server` on Debian). It is safe to use an
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existing Redis deployment if you have one.
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Once installed, check that Redis is running and accessible from the host running
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Synapse, for example by executing `echo PING | nc -q1 localhost 6379` and seeing
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a response of `+PONG`.
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The appropriate dependencies must also be installed for Synapse. If using a
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virtualenv, these can be installed with:
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```sh
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pip install "matrix-synapse[redis]"
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```
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Note that these dependencies are included when synapse is installed with `pip
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install matrix-synapse[all]`. They are also included in the debian packages from
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`matrix.org` and in the docker images at
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https://hub.docker.com/r/matrixdotorg/synapse/.
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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. See
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[reverse_proxy.md](reverse_proxy.md) for information on setting up a reverse
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proxy.
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When using workers, each worker process has its own configuration file which
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contains settings specific to that worker, such as the HTTP listener that it
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provides (if any), logging configuration, etc.
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Normally, the worker processes are configured to read from a shared
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configuration file as well as the worker-specific configuration files. This
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makes it easier to keep common configuration settings synchronised across all
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the processes.
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The main process is somewhat special in this respect: it does not normally
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need its own configuration file and can take all of its configuration from the
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shared configuration file.
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### Shared configuration
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Normally, only a couple of changes are needed to make an existing configuration
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file suitable for use with workers. First, you need to enable an "HTTP replication
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listener" for the main process; and secondly, you need to enable redis-based
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replication. Optionally, a shared secret can be used to authenticate HTTP
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traffic between workers. For example:
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```yaml
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# extend the existing `listeners` section. This defines the ports that the
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# main process will listen on.
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listeners:
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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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# Add a random shared secret to authenticate traffic.
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worker_replication_secret: ""
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redis:
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enabled: true
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```
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See the sample config for the full documentation of each option.
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Under **no circumstances** should the replication listener be exposed to the
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public internet; it has no authentication and is unencrypted.
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### Worker configuration
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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`), and you should specify a unique name for the worker
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(`worker_name`). The currently available worker applications are listed below.
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You must also specify the HTTP replication endpoint that it should talk to on
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the main synapse process. `worker_replication_host` should specify the host of
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the main synapse and `worker_replication_http_port` should point to the HTTP
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replication port. If the worker will handle HTTP requests then the
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`worker_listeners` option should be set with a `http` listener, in the same way
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as the `listeners` option in the shared config.
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For example:
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```yaml
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worker_app: synapse.app.generic_worker
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worker_name: worker1
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# The replication listener on the main synapse process.
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worker_replication_host: 127.0.0.1
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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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- federation
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worker_log_config: /home/matrix/synapse/config/worker1_log_config.yaml
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```
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...is a full configuration for a generic worker instance, which will expose a
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plain HTTP endpoint on port 8083 separately serving various endpoints, e.g.
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`/sync`, which are listed below.
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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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### Running Synapse with workers
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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
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[synctl_workers.md](synctl_workers.md).
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## Available worker applications
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### `synapse.app.generic_worker`
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This worker can handle API requests matching the following regular
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expressions:
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# Sync requests
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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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# Federation requests
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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/get_groups_publicised$
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^/_matrix/key/v2/query
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# Inbound federation transaction request
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^/_matrix/federation/v1/send/
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# Client API requests
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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)/account/3pid$
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^/_matrix/client/(api/v1|r0|unstable)/devices$
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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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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/event/
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^/_matrix/client/(api/v1|r0|unstable)/joined_rooms$
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^/_matrix/client/(api/v1|r0|unstable)/search$
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# Registration/login requests
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^/_matrix/client/(api/v1|r0|unstable)/login$
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^/_matrix/client/(r0|unstable)/register$
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# Event sending requests
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^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/redact
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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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Additionally, the following REST endpoints can be handled for GET requests:
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^/_matrix/federation/v1/groups/
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Pagination requests can also be handled, but all requests for a given
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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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Additionally, the following endpoints should be included if Synapse is configured
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to use SSO (you only need to include the ones for whichever SSO provider you're
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using):
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# for all SSO providers
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^/_matrix/client/(api/v1|r0|unstable)/login/sso/redirect
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^/_synapse/client/pick_idp$
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^/_synapse/client/pick_username
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^/_synapse/client/new_user_consent$
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^/_synapse/client/sso_register$
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# OpenID Connect requests.
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^/_synapse/client/oidc/callback$
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# SAML requests.
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^/_synapse/client/saml2/authn_response$
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# CAS requests.
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^/_matrix/client/(api/v1|r0|unstable)/login/cas/ticket$
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Ensure that all SSO logins go to a single process.
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For multiple workers not handling the SSO endpoints properly, see
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[#7530](https://github.com/matrix-org/synapse/issues/7530) and
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[#9427](https://github.com/matrix-org/synapse/issues/9427).
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Note that a HTTP listener with `client` and `federation` resources must be
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configured in the `worker_listeners` option in the worker config.
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#### Load balancing
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It is possible to run multiple instances of this worker app, with incoming requests
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being load-balanced between them by the reverse-proxy. However, different endpoints
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have different characteristics and so admins
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may wish to run multiple groups of workers handling different endpoints so that
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load balancing can be done in different ways.
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For `/sync` and `/initialSync` requests it will be more efficient if all
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requests from a particular user are routed to a single instance. Extracting a
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user ID from the access token or `Authorization` header is currently left as an
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exercise for the reader. Admins may additionally wish to separate out `/sync`
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requests that have a `since` query parameter from those that don't (and
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`/initialSync`), as requests that don't are known as "initial sync" that happens
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when a user logs in on a new device and can be *very* resource intensive, so
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isolating these requests will stop them from interfering with other users ongoing
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syncs.
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Federation and client requests can be balanced via simple round robin.
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The inbound federation transaction request `^/_matrix/federation/v1/send/`
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should be balanced by source IP so that transactions from the same remote server
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go to the same process.
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Registration/login requests can be handled separately purely to help ensure that
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unexpected load doesn't affect new logins and sign ups.
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Finally, event sending requests can be balanced by the room ID in the URI (or
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the full URI, or even just round robin), the room ID is the path component after
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`/rooms/`. If there is a large bridge connected that is sending or may send lots
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of events, then a dedicated set of workers can be provisioned to limit the
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effects of bursts of events from that bridge on events sent by normal users.
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#### Stream writers
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Additionally, there is *experimental* support for moving writing of specific
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streams (such as events) off of the main process to a particular worker. (This
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is only supported with Redis-based replication.)
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Currently supported streams are `events` and `typing`.
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To enable this, the worker must have a HTTP replication listener configured,
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have a `worker_name` and be listed in the `instance_map` config. For example to
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move event persistence off to a dedicated worker, the shared configuration would
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include:
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```yaml
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instance_map:
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event_persister1:
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host: localhost
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port: 8034
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stream_writers:
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events: event_persister1
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```
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The `events` stream also experimentally supports having multiple writers, where
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work is sharded between them by room ID. Note that you *must* restart all worker
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instances when adding or removing event persisters. An example `stream_writers`
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configuration with multiple writers:
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```yaml
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stream_writers:
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events:
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- event_persister1
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- event_persister2
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```
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#### Background tasks
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There is also *experimental* support for moving background tasks to a separate
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worker. Background tasks are run periodically or started via replication. Exactly
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which tasks are configured to run depends on your Synapse configuration (e.g. if
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stats is enabled).
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To enable this, the worker must have a `worker_name` and can be configured to run
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background tasks. For example, to move background tasks to a dedicated worker,
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the shared configuration would include:
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```yaml
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run_background_tasks_on: background_worker
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```
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You might also wish to investigate the `update_user_directory` and
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`media_instance_running_background_jobs` settings.
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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 push notifications.
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To run multiple instances at once the `pusher_instances` option should list all
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pusher instances by their worker name, e.g.:
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```yaml
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pusher_instances:
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- pusher_worker1
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- pusher_worker2
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```
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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 appservice 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_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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If running multiple federation senders then you must list each
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instance in the `federation_sender_instances` option by their `worker_name`.
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All instances must be stopped and started when adding or removing instances.
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For example:
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```yaml
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federation_sender_instances:
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- federation_sender1
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- federation_sender2
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```
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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 that if running multiple media repositories they must be on the same server
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and you must configure a single instance to run the background tasks, e.g.:
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```yaml
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media_instance_running_background_jobs: "media-repository-1"
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```
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Note that if a reverse proxy is used , then `/_matrix/media/` must be routed for both inbound client and federation requests (if they are handled separately).
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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
|
|
|
|
### Historical apps
|
|
|
|
*Note:* Historically there used to be more apps, however they have been
|
|
amalgamated into a single `synapse.app.generic_worker` app. The remaining apps
|
|
are ones that do specific processing unrelated to requests, e.g. the `pusher`
|
|
that handles sending out push notifications for new events. The intention is for
|
|
all these to be folded into the `generic_worker` app and to use config to define
|
|
which processes handle the various proccessing such as push notifications.
|
|
|
|
|
|
## Migration from old config
|
|
|
|
There are two main independent changes that have been made: introducing Redis
|
|
support and merging apps into `synapse.app.generic_worker`. Both these changes
|
|
are backwards compatible and so no changes to the config are required, however
|
|
server admins are encouraged to plan to migrate to Redis as the old style direct
|
|
TCP replication config is deprecated.
|
|
|
|
To migrate to Redis add the `redis` config as above, and optionally remove the
|
|
TCP `replication` listener from master and `worker_replication_port` from worker
|
|
config.
|
|
|
|
To migrate apps to use `synapse.app.generic_worker` simply update the
|
|
`worker_app` option in the worker configs, and where worker are started (e.g.
|
|
in systemd service files, but not required for synctl).
|
|
|
|
|
|
## Architectural diagram
|
|
|
|
The following shows an example setup using Redis and a reverse proxy:
|
|
|
|
```
|
|
Clients & Federation
|
|
|
|
|
v
|
|
+-----------+
|
|
| |
|
|
| Reverse |
|
|
| Proxy |
|
|
| |
|
|
+-----------+
|
|
| | |
|
|
| | | HTTP requests
|
|
+-------------------+ | +-----------+
|
|
| +---+ |
|
|
| | |
|
|
v v v
|
|
+--------------+ +--------------+ +--------------+ +--------------+
|
|
| Main | | Generic | | Generic | | Event |
|
|
| Process | | Worker 1 | | Worker 2 | | Persister |
|
|
+--------------+ +--------------+ +--------------+ +--------------+
|
|
^ ^ | ^ | | ^ | ^ ^
|
|
| | | | | | | | | |
|
|
| | | | | HTTP | | | | |
|
|
| +----------+<--|---|---------+ | | | |
|
|
| | +-------------|-->+----------+ |
|
|
| | | |
|
|
| | | |
|
|
v v v v
|
|
====================================================================
|
|
Redis pub/sub channel
|
|
```
|