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+                <ol class="chapter"><li class="chapter-item expanded affix "><li class="part-title">Introduction</li><li class="chapter-item expanded "><a href="welcome_and_overview.html">Welcome and Overview</a></li><li class="chapter-item expanded affix "><li class="part-title">Setup</li><li class="chapter-item expanded "><a href="setup/installation.html">Installation</a></li><li class="chapter-item expanded "><a href="postgres.html">Using Postgres</a></li><li class="chapter-item expanded "><a href="reverse_proxy.html">Configuring a Reverse Proxy</a></li><li class="chapter-item expanded "><a href="setup/forward_proxy.html">Configuring a Forward/Outbound Proxy</a></li><li class="chapter-item expanded "><a href="turn-howto.html">Configuring a Turn Server</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="setup/turn/coturn.html">coturn TURN server</a></li><li class="chapter-item expanded "><a href="setup/turn/eturnal.html">eturnal TURN 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+
+                        <h1 id="scaling-synapse-via-workers"><a class="header" href="#scaling-synapse-via-workers">Scaling synapse via workers</a></h1>
+<p>For small instances it is recommended to run Synapse in the default monolith mode.
+For larger instances where performance is a concern it can be helpful to split
+out functionality into multiple separate python processes. These processes are
+called 'workers', and are (eventually) intended to scale horizontally
+independently.</p>
+<p>Synapse's worker support is under active development and subject to change as
+we attempt to rapidly scale ever larger Synapse instances. However we are
+documenting it here to help admins needing a highly scalable Synapse instance
+similar to the one running <code>matrix.org</code>.</p>
+<p>All processes continue to share the same database instance, and as such,
+workers only work with PostgreSQL-based Synapse deployments. SQLite should only
+be used for demo purposes and any admin considering workers should already be
+running PostgreSQL.</p>
+<p>See also <a href="https://matrix.org/blog/2020/11/03/how-we-fixed-synapses-scalability">Matrix.org blog post</a>
+for a higher level overview.</p>
+<h2 id="main-processworker-communication"><a class="header" href="#main-processworker-communication">Main process/worker communication</a></h2>
+<p>The processes communicate with each other via a Synapse-specific protocol called
+'replication' (analogous to MySQL- or Postgres-style database replication) which
+feeds streams of newly written data between processes so they can be kept in
+sync with the database state.</p>
+<p>When configured to do so, Synapse uses a
+<a href="https://redis.io/docs/manual/pubsub/">Redis pub/sub channel</a> to send the replication
+stream between all configured Synapse processes. Additionally, processes may
+make HTTP requests to each other, primarily for operations which need to wait
+for a reply ─ such as sending an event.</p>
+<p>All the workers and the main process connect to Redis, which relays replication
+commands between processes.</p>
+<p>If Redis support is enabled Synapse will use it as a shared cache, as well as a
+pub/sub mechanism.</p>
+<p>See the <a href="#architectural-diagram">Architectural diagram</a> section at the end for
+a visualisation of what this looks like.</p>
+<h2 id="setting-up-workers"><a class="header" href="#setting-up-workers">Setting up workers</a></h2>
+<p>A Redis server is required to manage the communication between the processes.
+The Redis server should be installed following the normal procedure for your
+distribution (e.g. <code>apt install redis-server</code> on Debian). It is safe to use an
+existing Redis deployment if you have one.</p>
+<p>Once installed, check that Redis is running and accessible from the host running
+Synapse, for example by executing <code>echo PING | nc -q1 localhost 6379</code> and seeing
+a response of <code>+PONG</code>.</p>
+<p>The appropriate dependencies must also be installed for Synapse. If using a
+virtualenv, these can be installed with:</p>
+<pre><code class="language-sh">pip install &quot;matrix-synapse[redis]&quot;
+</code></pre>
+<p>Note that these dependencies are included when synapse is installed with <code>pip install matrix-synapse[all]</code>. They are also included in the debian packages from
+<code>packages.matrix.org</code> and in the docker images at
+https://hub.docker.com/r/ectorim/synapse/.</p>
+<p>To make effective use of the workers, you will need to configure an HTTP
+reverse-proxy such as nginx or haproxy, which will direct incoming requests to
+the correct worker, or to the main synapse instance. See
+<a href="reverse_proxy.html">the reverse proxy documentation</a> for information on setting up a reverse
+proxy.</p>
+<p>When using workers, each worker process has its own configuration file which
+contains settings specific to that worker, such as the HTTP listener that it
+provides (if any), logging configuration, etc.</p>
+<p>Normally, the worker processes are configured to read from a shared
+configuration file as well as the worker-specific configuration files. This
+makes it easier to keep common configuration settings synchronised across all
+the processes.</p>
+<p>The main process is somewhat special in this respect: it does not normally
+need its own configuration file and can take all of its configuration from the
+shared configuration file.</p>
+<h3 id="shared-configuration"><a class="header" href="#shared-configuration">Shared configuration</a></h3>
+<p>Normally, only a few changes are needed to make an existing configuration
+file suitable for use with workers:</p>
+<ul>
+<li>First, you need to enable an
+<a href="usage/configuration/config_documentation.html#listeners">&quot;HTTP replication listener&quot;</a>
+for the main process</li>
+<li>Secondly, you need to enable
+<a href="usage/configuration/config_documentation.html#redis">redis-based replication</a></li>
+<li>You will need to add an <a href="usage/configuration/config_documentation.html#instance_map"><code>instance_map</code></a>
+with the <code>main</code> process defined, as well as the relevant connection information from
+it's HTTP <code>replication</code> listener (defined in step 1 above).
+<ul>
+<li>Note that the <code>host</code> defined is the address the worker needs to look for the <code>main</code>
+process at, not necessarily the same address that is bound to.</li>
+<li>If you are using Unix sockets for the <code>replication</code> resource, make sure to
+use a <code>path</code> to the socket file instead of a <code>port</code>.</li>
+</ul>
+</li>
+<li>Optionally, a <a href="usage/configuration/config_documentation.html#worker_replication_secret">shared secret</a>
+can be used to authenticate HTTP traffic between workers. For example:</li>
+</ul>
+<pre><code class="language-yaml"># extend the existing `listeners` section. This defines the ports that the
+# main process will listen on.
+listeners:
+  # The HTTP replication port
+  - port: 9093
+    bind_address: '127.0.0.1'
+    type: http
+    resources:
+     - names: [replication]
+
+# Add a random shared secret to authenticate traffic.
+worker_replication_secret: &quot;&quot;
+
+redis:
+    enabled: true
+
+instance_map:
+    main:
+        host: 'localhost'
+        port: 9093
+</code></pre>
+<p>See the <a href="usage/configuration/config_documentation.html">configuration manual</a>
+for the full documentation of each option.</p>
+<p>Under <strong>no circumstances</strong> should the replication listener be exposed to the
+public internet; replication traffic is:</p>
+<ul>
+<li>always unencrypted</li>
+<li>unauthenticated, unless <a href="usage/configuration/config_documentation.html#worker_replication_secret"><code>worker_replication_secret</code></a>
+is configured</li>
+</ul>
+<h3 id="worker-configuration"><a class="header" href="#worker-configuration">Worker configuration</a></h3>
+<p>In the config file for each worker, you must specify:</p>
+<ul>
+<li>The type of worker (<a href="usage/configuration/config_documentation.html#worker_app"><code>worker_app</code></a>).
+The currently available worker applications are listed <a href="#available-worker-applications">below</a>.</li>
+<li>A unique name for the worker (<a href="usage/configuration/config_documentation.html#worker_name"><code>worker_name</code></a>).</li>
+<li>If handling HTTP requests, a <a href="usage/configuration/config_documentation.html#worker_listeners"><code>worker_listeners</code></a> option
+with an <code>http</code> listener.</li>
+<li><strong>Synapse 1.72 and older:</strong> if handling the <code>^/_matrix/client/v3/keys/upload</code> endpoint, the HTTP URI for
+the main process (<code>worker_main_http_uri</code>). This config option is no longer required and is ignored when running Synapse 1.73 and newer.</li>
+</ul>
+<p>For example:</p>
+<pre><code class="language-yaml">worker_app: synapse.app.generic_worker
+worker_name: generic_worker1
+
+worker_listeners:
+  - type: http
+    port: 8083
+    x_forwarded: true
+    resources:
+      - names: [client, federation]
+
+worker_log_config: /etc/matrix-synapse/generic-worker-log.yaml
+</code></pre>
+<p>...is a full configuration for a generic worker instance, which will expose a
+plain HTTP endpoint on port 8083 separately serving various endpoints, e.g.
+<code>/sync</code>, which are listed below.</p>
+<p>Obviously you should configure your reverse-proxy to route the relevant
+endpoints to the worker (<code>localhost:8083</code> in the above example).</p>
+<h3 id="running-synapse-with-workers"><a class="header" href="#running-synapse-with-workers">Running Synapse with workers</a></h3>
+<p>Finally, you need to start your worker processes. This can be done with either
+<code>synctl</code> or your distribution's preferred service manager such as <code>systemd</code>. We
+recommend the use of <code>systemd</code> where available: for information on setting up
+<code>systemd</code> to start synapse workers, see
+<a href="systemd-with-workers/">Systemd with Workers</a>. To use <code>synctl</code>, see
+<a href="synctl_workers.html">Using synctl with Workers</a>.</p>
+<h2 id="start-synapse-with-poetry"><a class="header" href="#start-synapse-with-poetry">Start Synapse with Poetry</a></h2>
+<p>The following applies to Synapse installations that have been installed from source using <code>poetry</code>.</p>
+<p>You can start the main Synapse process with Poetry by running the following command:</p>
+<pre><code class="language-console">poetry run synapse_homeserver --config-file [your homeserver.yaml]
+</code></pre>
+<p>For worker setups, you can run the following command</p>
+<pre><code class="language-console">poetry run synapse_worker --config-file [your homeserver.yaml] --config-file [your worker.yaml]
+</code></pre>
+<h2 id="available-worker-applications"><a class="header" href="#available-worker-applications">Available worker applications</a></h2>
+<h3 id="synapseappgeneric_worker"><a class="header" href="#synapseappgeneric_worker"><code>synapse.app.generic_worker</code></a></h3>
+<p>This worker can handle API requests matching the following regular expressions.
+These endpoints can be routed to any worker. If a worker is set up to handle a
+stream then, for maximum efficiency, additional endpoints should be routed to that
+worker: refer to the <a href="#stream-writers">stream writers</a> section below for further
+information.</p>
+<pre><code># Sync requests
+^/_matrix/client/(r0|v3)/sync$
+^/_matrix/client/(api/v1|r0|v3)/events$
+^/_matrix/client/(api/v1|r0|v3)/initialSync$
+^/_matrix/client/(api/v1|r0|v3)/rooms/[^/]+/initialSync$
+
+# Federation requests
+^/_matrix/federation/v1/event/
+^/_matrix/federation/v1/state/
+^/_matrix/federation/v1/state_ids/
+^/_matrix/federation/v1/backfill/
+^/_matrix/federation/v1/get_missing_events/
+^/_matrix/federation/v1/publicRooms
+^/_matrix/federation/v1/query/
+^/_matrix/federation/v1/make_join/
+^/_matrix/federation/v1/make_leave/
+^/_matrix/federation/(v1|v2)/send_join/
+^/_matrix/federation/(v1|v2)/send_leave/
+^/_matrix/federation/(v1|v2)/invite/
+^/_matrix/federation/v1/event_auth/
+^/_matrix/federation/v1/timestamp_to_event/
+^/_matrix/federation/v1/exchange_third_party_invite/
+^/_matrix/federation/v1/user/devices/
+^/_matrix/key/v2/query
+^/_matrix/federation/v1/hierarchy/
+
+# Inbound federation transaction request
+^/_matrix/federation/v1/send/
+
+# Client API requests
+^/_matrix/client/(api/v1|r0|v3|unstable)/createRoom$
+^/_matrix/client/(api/v1|r0|v3|unstable)/publicRooms$
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/joined_members$
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/context/.*$
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/members$
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/state$
+^/_matrix/client/v1/rooms/.*/hierarchy$
+^/_matrix/client/(v1|unstable)/rooms/.*/relations/
+^/_matrix/client/v1/rooms/.*/threads$
+^/_matrix/client/unstable/im.nheko.summary/rooms/.*/summary$
+^/_matrix/client/(r0|v3|unstable)/account/3pid$
+^/_matrix/client/(r0|v3|unstable)/account/whoami$
+^/_matrix/client/(r0|v3|unstable)/devices$
+^/_matrix/client/versions$
+^/_matrix/client/(api/v1|r0|v3|unstable)/voip/turnServer$
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/event/
+^/_matrix/client/(api/v1|r0|v3|unstable)/joined_rooms$
+^/_matrix/client/v1/rooms/.*/timestamp_to_event$
+^/_matrix/client/(api/v1|r0|v3|unstable/.*)/rooms/.*/aliases
+^/_matrix/client/(api/v1|r0|v3|unstable)/search$
+^/_matrix/client/(r0|v3|unstable)/user/.*/filter(/|$)
+^/_matrix/client/(api/v1|r0|v3|unstable)/directory/room/.*$
+^/_matrix/client/(r0|v3|unstable)/capabilities$
+^/_matrix/client/(r0|v3|unstable)/notifications$
+
+# Encryption requests
+^/_matrix/client/(r0|v3|unstable)/keys/query$
+^/_matrix/client/(r0|v3|unstable)/keys/changes$
+^/_matrix/client/(r0|v3|unstable)/keys/claim$
+^/_matrix/client/(r0|v3|unstable)/room_keys/
+^/_matrix/client/(r0|v3|unstable)/keys/upload/
+
+# Registration/login requests
+^/_matrix/client/(api/v1|r0|v3|unstable)/login$
+^/_matrix/client/(r0|v3|unstable)/register$
+^/_matrix/client/(r0|v3|unstable)/register/available$
+^/_matrix/client/v1/register/m.login.registration_token/validity$
+^/_matrix/client/(r0|v3|unstable)/password_policy$
+
+# Event sending requests
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/redact
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/send
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/state/
+^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/(join|invite|leave|ban|unban|kick)$
+^/_matrix/client/(api/v1|r0|v3|unstable)/join/
+^/_matrix/client/(api/v1|r0|v3|unstable)/knock/
+^/_matrix/client/(api/v1|r0|v3|unstable)/profile/
+
+# Account data requests
+^/_matrix/client/(r0|v3|unstable)/.*/tags
+^/_matrix/client/(r0|v3|unstable)/.*/account_data
+
+# Receipts requests
+^/_matrix/client/(r0|v3|unstable)/rooms/.*/receipt
+^/_matrix/client/(r0|v3|unstable)/rooms/.*/read_markers
+
+# Presence requests
+^/_matrix/client/(api/v1|r0|v3|unstable)/presence/
+
+# User directory search requests
+^/_matrix/client/(r0|v3|unstable)/user_directory/search$
+</code></pre>
+<p>Additionally, the following REST endpoints can be handled for GET requests:</p>
+<pre><code>^/_matrix/client/(api/v1|r0|v3|unstable)/pushrules/
+</code></pre>
+<p>Pagination requests can also be handled, but all requests for a given
+room must be routed to the same instance. Additionally, care must be taken to
+ensure that the purge history admin API is not used while pagination requests
+for the room are in flight:</p>
+<pre><code>^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/messages$
+</code></pre>
+<p>Additionally, the following endpoints should be included if Synapse is configured
+to use SSO (you only need to include the ones for whichever SSO provider you're
+using):</p>
+<pre><code># for all SSO providers
+^/_matrix/client/(api/v1|r0|v3|unstable)/login/sso/redirect
+^/_synapse/client/pick_idp$
+^/_synapse/client/pick_username
+^/_synapse/client/new_user_consent$
+^/_synapse/client/sso_register$
+
+# OpenID Connect requests.
+^/_synapse/client/oidc/callback$
+
+# SAML requests.
+^/_synapse/client/saml2/authn_response$
+
+# CAS requests.
+^/_matrix/client/(api/v1|r0|v3|unstable)/login/cas/ticket$
+</code></pre>
+<p>Ensure that all SSO logins go to a single process.
+For multiple workers not handling the SSO endpoints properly, see
+<a href="https://github.com/matrix-org/synapse/issues/7530">#7530</a> and
+<a href="https://github.com/matrix-org/synapse/issues/9427">#9427</a>.</p>
+<p>Note that a <a href="usage/configuration/config_documentation.html#listeners">HTTP listener</a>
+with <code>client</code> and <code>federation</code> <code>resources</code> must be configured in the
+<a href="usage/configuration/config_documentation.html#worker_listeners"><code>worker_listeners</code></a>
+option in the worker config.</p>
+<h4 id="load-balancing"><a class="header" href="#load-balancing">Load balancing</a></h4>
+<p>It is possible to run multiple instances of this worker app, with incoming requests
+being load-balanced between them by the reverse-proxy. However, different endpoints
+have different characteristics and so admins
+may wish to run multiple groups of workers handling different endpoints so that
+load balancing can be done in different ways.</p>
+<p>For <code>/sync</code> and <code>/initialSync</code> requests it will be more efficient if all
+requests from a particular user are routed to a single instance. This can
+be done in reverse proxy by extracting username part from the users access token.</p>
+<p>Admins may additionally wish to separate out <code>/sync</code>
+requests that have a <code>since</code> query parameter from those that don't (and
+<code>/initialSync</code>), as requests that don't are known as &quot;initial sync&quot; that happens
+when a user logs in on a new device and can be <em>very</em> resource intensive, so
+isolating these requests will stop them from interfering with other users ongoing
+syncs.</p>
+<p>Example <code>nginx</code> configuration snippet that handles the cases above. This is just an
+example and probably requires some changes according to your particular setup:</p>
+<pre><code class="language-nginx"># Choose sync worker based on the existence of &quot;since&quot; query parameter
+map $arg_since $sync {
+    default synapse_sync;
+    '' synapse_initial_sync;
+}
+
+# Extract username from access token passed as URL parameter
+map $arg_access_token $accesstoken_from_urlparam {
+    # Defaults to just passing back the whole accesstoken
+    default   $arg_access_token;
+    # Try to extract username part from accesstoken URL parameter
+    &quot;~syt_(?&lt;username&gt;.*?)_.*&quot;           $username;
+}
+
+# Extract username from access token passed as authorization header
+map $http_authorization $mxid_localpart {
+    # Defaults to just passing back the whole accesstoken
+    default                              $http_authorization;
+    # Try to extract username part from accesstoken header
+    &quot;~Bearer syt_(?&lt;username&gt;.*?)_.*&quot;    $username;
+    # if no authorization-header exist, try mapper for URL parameter &quot;access_token&quot;
+    &quot;&quot;                                   $accesstoken_from_urlparam;
+}
+
+upstream synapse_initial_sync {
+    # Use the username mapper result for hash key
+    hash $mxid_localpart consistent;
+    server 127.0.0.1:8016;
+    server 127.0.0.1:8036;
+}
+
+upstream synapse_sync {
+    # Use the username mapper result for hash key
+    hash $mxid_localpart consistent;
+    server 127.0.0.1:8013;
+    server 127.0.0.1:8037;
+    server 127.0.0.1:8038;
+    server 127.0.0.1:8039;
+}
+
+# Sync initial/normal
+location ~ ^/_matrix/client/(r0|v3)/sync$ {
+	proxy_pass http://$sync;
+}
+
+# Normal sync
+location ~ ^/_matrix/client/(api/v1|r0|v3)/events$ {
+	proxy_pass http://synapse_sync;
+}
+
+# Initial_sync
+location ~ ^/_matrix/client/(api/v1|r0|v3)/initialSync$ {
+	proxy_pass http://synapse_initial_sync;
+}
+location ~ ^/_matrix/client/(api/v1|r0|v3)/rooms/[^/]+/initialSync$ {
+	proxy_pass http://synapse_initial_sync;
+}
+</code></pre>
+<p>Federation and client requests can be balanced via simple round robin.</p>
+<p>The inbound federation transaction request <code>^/_matrix/federation/v1/send/</code>
+should be balanced by source IP so that transactions from the same remote server
+go to the same process.</p>
+<p>Registration/login requests can be handled separately purely to help ensure that
+unexpected load doesn't affect new logins and sign ups.</p>
+<p>Finally, event sending requests can be balanced by the room ID in the URI (or
+the full URI, or even just round robin), the room ID is the path component after
+<code>/rooms/</code>. If there is a large bridge connected that is sending or may send lots
+of events, then a dedicated set of workers can be provisioned to limit the
+effects of bursts of events from that bridge on events sent by normal users.</p>
+<h4 id="stream-writers"><a class="header" href="#stream-writers">Stream writers</a></h4>
+<p>Additionally, the writing of specific streams (such as events) can be moved off
+of the main process to a particular worker.</p>
+<p>To enable this, the worker must have:</p>
+<ul>
+<li>An <a href="usage/configuration/config_documentation.html#listeners">HTTP <code>replication</code> listener</a> configured,</li>
+<li>Have a <a href="usage/configuration/config_documentation.html#worker_name"><code>worker_name</code></a>
+and be listed in the <a href="usage/configuration/config_documentation.html#instance_map"><code>instance_map</code></a>
+config.</li>
+<li>Have the main process declared on the <a href="usage/configuration/config_documentation.html#instance_map"><code>instance_map</code></a> as well.</li>
+</ul>
+<p>Note: The same worker can handle multiple streams, but unless otherwise documented,
+each stream can only have a single writer.</p>
+<p>For example, to move event persistence off to a dedicated worker, the shared
+configuration would include:</p>
+<pre><code class="language-yaml">instance_map:
+    main:
+        host: localhost
+        port: 8030
+    event_persister1:
+        host: localhost
+        port: 8034
+
+stream_writers:
+    events: event_persister1
+</code></pre>
+<p>An example for a stream writer instance:</p>
+<pre><code class="language-yaml">worker_app: synapse.app.generic_worker
+worker_name: event_persister1
+
+worker_listeners:
+  - type: http
+    port: 8034
+    resources:
+      - names: [replication]
+
+  # Enable listener if this stream writer handles endpoints for the `typing` or
+  # `to_device` streams. Uses a different port to the `replication` listener to
+  # avoid exposing the `replication` listener publicly.
+  #
+  #- type: http
+  #  port: 8035
+  #  x_forwarded: true
+  #  resources:
+  #    - names: [client]
+
+worker_log_config: /etc/matrix-synapse/event-persister-log.yaml
+</code></pre>
+<p>Some of the streams have associated endpoints which, for maximum efficiency, should
+be routed to the workers handling that stream. See below for the currently supported
+streams and the endpoints associated with them:</p>
+<h5 id="the-events-stream"><a class="header" href="#the-events-stream">The <code>events</code> stream</a></h5>
+<p>The <code>events</code> stream experimentally supports having multiple writer workers, where load
+is sharded between them by room ID. Each writer is called an <em>event persister</em>. They are
+responsible for</p>
+<ul>
+<li>receiving new events,</li>
+<li>linking them to those already in the room <a href="development/room-dag-concepts.html">DAG</a>,</li>
+<li>persisting them to the DB, and finally</li>
+<li>updating the events stream.</li>
+</ul>
+<p>Because load is sharded in this way, you <em>must</em> restart all worker instances when
+adding or removing event persisters.</p>
+<p>An <code>event_persister</code> should not be mistaken for an <code>event_creator</code>.
+An <code>event_creator</code> listens for requests from clients to create new events and does
+so. It will then pass those events over HTTP replication to any configured event
+persisters (or the main process if none are configured).</p>
+<p>Note that <code>event_creator</code>s and <code>event_persister</code>s are implemented using the same
+<a href="#synapseappgeneric_worker"><code>synapse.app.generic_worker</code></a>.</p>
+<p>An example <a href="usage/configuration/config_documentation.html#stream_writers"><code>stream_writers</code></a>
+configuration with multiple writers:</p>
+<pre><code class="language-yaml">stream_writers:
+    events:
+        - event_persister1
+        - event_persister2
+</code></pre>
+<h5 id="the-typing-stream"><a class="header" href="#the-typing-stream">The <code>typing</code> stream</a></h5>
+<p>The following endpoints should be routed directly to the worker configured as
+the stream writer for the <code>typing</code> stream:</p>
+<pre><code>^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/typing
+</code></pre>
+<h5 id="the-to_device-stream"><a class="header" href="#the-to_device-stream">The <code>to_device</code> stream</a></h5>
+<p>The following endpoints should be routed directly to the worker configured as
+the stream writer for the <code>to_device</code> stream:</p>
+<pre><code>^/_matrix/client/(r0|v3|unstable)/sendToDevice/
+</code></pre>
+<h5 id="the-account_data-stream"><a class="header" href="#the-account_data-stream">The <code>account_data</code> stream</a></h5>
+<p>The following endpoints should be routed directly to the worker configured as
+the stream writer for the <code>account_data</code> stream:</p>
+<pre><code>^/_matrix/client/(r0|v3|unstable)/.*/tags
+^/_matrix/client/(r0|v3|unstable)/.*/account_data
+</code></pre>
+<h5 id="the-receipts-stream"><a class="header" href="#the-receipts-stream">The <code>receipts</code> stream</a></h5>
+<p>The following endpoints should be routed directly to the worker configured as
+the stream writer for the <code>receipts</code> stream:</p>
+<pre><code>^/_matrix/client/(r0|v3|unstable)/rooms/.*/receipt
+^/_matrix/client/(r0|v3|unstable)/rooms/.*/read_markers
+</code></pre>
+<h5 id="the-presence-stream"><a class="header" href="#the-presence-stream">The <code>presence</code> stream</a></h5>
+<p>The following endpoints should be routed directly to the worker configured as
+the stream writer for the <code>presence</code> stream:</p>
+<pre><code>^/_matrix/client/(api/v1|r0|v3|unstable)/presence/
+</code></pre>
+<h5 id="the-push_rules-stream"><a class="header" href="#the-push_rules-stream">The <code>push_rules</code> stream</a></h5>
+<p>The following endpoints should be routed directly to the worker configured as
+the stream writer for the <code>push</code> stream:</p>
+<pre><code>^/_matrix/client/(api/v1|r0|v3|unstable)/pushrules/
+</code></pre>
+<h4 id="restrict-outbound-federation-traffic-to-a-specific-set-of-workers"><a class="header" href="#restrict-outbound-federation-traffic-to-a-specific-set-of-workers">Restrict outbound federation traffic to a specific set of workers</a></h4>
+<p>The
+<a href="usage/configuration/config_documentation.html#outbound_federation_restricted_to"><code>outbound_federation_restricted_to</code></a>
+configuration is useful to make sure outbound federation traffic only goes through a
+specified subset of workers. This allows you to set more strict access controls (like a
+firewall) for all workers and only allow the <code>federation_sender</code>'s to contact the
+outside world.</p>
+<pre><code class="language-yaml">instance_map:
+    main:
+        host: localhost
+        port: 8030
+    federation_sender1:
+        host: localhost
+        port: 8034
+
+outbound_federation_restricted_to:
+  - federation_sender1
+
+worker_replication_secret: &quot;secret_secret&quot;
+</code></pre>
+<h4 id="background-tasks"><a class="header" href="#background-tasks">Background tasks</a></h4>
+<p>There is also support for moving background tasks to a separate
+worker. Background tasks are run periodically or started via replication. Exactly
+which tasks are configured to run depends on your Synapse configuration (e.g. if
+stats is enabled). This worker doesn't handle any REST endpoints itself.</p>
+<p>To enable this, the worker must have a unique
+<a href="usage/configuration/config_documentation.html#worker_name"><code>worker_name</code></a>
+and can be configured to run background tasks. For example, to move background tasks
+to a dedicated worker, the shared configuration would include:</p>
+<pre><code class="language-yaml">run_background_tasks_on: background_worker
+</code></pre>
+<p>You might also wish to investigate the
+<a href="#updating-the-user-directory"><code>update_user_directory_from_worker</code></a> and
+<a href="#synapseappmedia_repository"><code>media_instance_running_background_jobs</code></a> settings.</p>
+<p>An example for a dedicated background worker instance:</p>
+<pre><code class="language-yaml">worker_app: synapse.app.generic_worker
+worker_name: background_worker
+
+worker_log_config: /etc/matrix-synapse/background-worker-log.yaml
+</code></pre>
+<h4 id="updating-the-user-directory"><a class="header" href="#updating-the-user-directory">Updating the User Directory</a></h4>
+<p>You can designate one generic worker to update the user directory.</p>
+<p>Specify its name in the <a href="usage/configuration/config_documentation.html#update_user_directory_from_worker">shared configuration</a>
+as follows:</p>
+<pre><code class="language-yaml">update_user_directory_from_worker: worker_name
+</code></pre>
+<p>This work cannot be load-balanced; please ensure the main process is restarted
+after setting this option in the shared configuration!</p>
+<p>User directory updates allow REST endpoints matching the following regular
+expressions to work:</p>
+<pre><code>^/_matrix/client/(r0|v3|unstable)/user_directory/search$
+</code></pre>
+<p>The above endpoints can be routed to any worker, though you may choose to route
+it to the chosen user directory worker.</p>
+<p>This style of configuration supersedes the legacy <code>synapse.app.user_dir</code>
+worker application type.</p>
+<h4 id="notifying-application-services"><a class="header" href="#notifying-application-services">Notifying Application Services</a></h4>
+<p>You can designate one generic worker to send output traffic to Application Services.
+Doesn't handle any REST endpoints itself, but you should specify its name in the
+<a href="usage/configuration/config_documentation.html#notify_appservices_from_worker">shared configuration</a>
+as follows:</p>
+<pre><code class="language-yaml">notify_appservices_from_worker: worker_name
+</code></pre>
+<p>This work cannot be load-balanced; please ensure the main process is restarted
+after setting this option in the shared configuration!</p>
+<p>This style of configuration supersedes the legacy <code>synapse.app.appservice</code>
+worker application type.</p>
+<h4 id="push-notifications"><a class="header" href="#push-notifications">Push Notifications</a></h4>
+<p>You can designate generic worker to sending push notifications to
+a <a href="https://spec.matrix.org/v1.5/push-gateway-api/">push gateway</a> such as
+<a href="https://github.com/matrix-org/sygnal">sygnal</a> and email.</p>
+<p>This will stop the main process sending push notifications.</p>
+<p>The workers responsible for sending push notifications can be defined using the
+<a href="usage/configuration/config_documentation.html#pusher_instances"><code>pusher_instances</code></a>
+option. For example:</p>
+<pre><code class="language-yaml">pusher_instances:
+  - pusher_worker1
+  - pusher_worker2
+</code></pre>
+<p>Multiple workers can be added to this map, in which case the work is balanced
+across them. Ensure the main process and all pusher workers are restarted after changing
+this option.</p>
+<p>These workers don't need to accept incoming HTTP requests to send push notifications,
+so no additional reverse proxy configuration is required for pusher workers.</p>
+<p>This style of configuration supersedes the legacy <code>synapse.app.pusher</code>
+worker application type.</p>
+<h3 id="synapseapppusher"><a class="header" href="#synapseapppusher"><code>synapse.app.pusher</code></a></h3>
+<p>It is likely this option will be deprecated in the future and is not recommended for new
+installations. Instead, <a href="#push-notifications">use <code>synapse.app.generic_worker</code> with the <code>pusher_instances</code></a>.</p>
+<p>Handles sending push notifications to sygnal and email. Doesn't handle any
+REST endpoints itself, but you should set
+<a href="usage/configuration/config_documentation.html#start_pushers"><code>start_pushers: false</code></a> in the
+shared configuration file to stop the main synapse sending push notifications.</p>
+<p>To run multiple instances at once the
+<a href="usage/configuration/config_documentation.html#pusher_instances"><code>pusher_instances</code></a>
+option should list all pusher instances by their
+<a href="usage/configuration/config_documentation.html#worker_name"><code>worker_name</code></a>, e.g.:</p>
+<pre><code class="language-yaml">start_pushers: false
+pusher_instances:
+    - pusher_worker1
+    - pusher_worker2
+</code></pre>
+<p>An example for a pusher instance:</p>
+<pre><code class="language-yaml">worker_app: synapse.app.pusher
+worker_name: pusher_worker1
+
+worker_log_config: /etc/matrix-synapse/pusher-worker-log.yaml
+</code></pre>
+<h3 id="synapseappappservice"><a class="header" href="#synapseappappservice"><code>synapse.app.appservice</code></a></h3>
+<p><strong>Deprecated as of Synapse v1.59.</strong> <a href="#notifying-application-services">Use <code>synapse.app.generic_worker</code> with the
+<code>notify_appservices_from_worker</code> option instead.</a></p>
+<p>Handles sending output traffic to Application Services. Doesn't handle any
+REST endpoints itself, but you should set <code>notify_appservices: False</code> in the
+shared configuration file to stop the main synapse sending appservice notifications.</p>
+<p>Note this worker cannot be load-balanced: only one instance should be active.</p>
+<h3 id="synapseappfederation_sender"><a class="header" href="#synapseappfederation_sender"><code>synapse.app.federation_sender</code></a></h3>
+<p>It is likely this option will be deprecated in the future and not recommended for
+new installations. Instead, <a href="usage/configuration/config_documentation.html#federation_sender_instances">use <code>synapse.app.generic_worker</code> with the <code>federation_sender_instances</code></a>.</p>
+<p>Handles sending federation traffic to other servers. Doesn't handle any
+REST endpoints itself, but you should set
+<a href="usage/configuration/config_documentation.html#send_federation"><code>send_federation: false</code></a>
+in the shared configuration file to stop the main synapse sending this traffic.</p>
+<p>If running multiple federation senders then you must list each
+instance in the
+<a href="usage/configuration/config_documentation.html#federation_sender_instances"><code>federation_sender_instances</code></a>
+option by their
+<a href="usage/configuration/config_documentation.html#worker_name"><code>worker_name</code></a>.
+All instances must be stopped and started when adding or removing instances.
+For example:</p>
+<pre><code class="language-yaml">send_federation: false
+federation_sender_instances:
+    - federation_sender1
+    - federation_sender2
+</code></pre>
+<p>An example for a federation sender instance:</p>
+<pre><code class="language-yaml">worker_app: synapse.app.federation_sender
+worker_name: federation_sender1
+
+worker_log_config: /etc/matrix-synapse/federation-sender-log.yaml
+</code></pre>
+<h3 id="synapseappmedia_repository"><a class="header" href="#synapseappmedia_repository"><code>synapse.app.media_repository</code></a></h3>
+<p>Handles the media repository. It can handle all endpoints starting with:</p>
+<pre><code>/_matrix/media/
+</code></pre>
+<p>... and the following regular expressions matching media-specific administration APIs:</p>
+<pre><code>^/_synapse/admin/v1/purge_media_cache$
+^/_synapse/admin/v1/room/.*/media.*$
+^/_synapse/admin/v1/user/.*/media.*$
+^/_synapse/admin/v1/media/.*$
+^/_synapse/admin/v1/quarantine_media/.*$
+^/_synapse/admin/v1/users/.*/media$
+</code></pre>
+<p>You should also set
+<a href="usage/configuration/config_documentation.html#enable_media_repo"><code>enable_media_repo: False</code></a>
+in the shared configuration
+file to stop the main synapse running background jobs related to managing the
+media repository. Note that doing so will prevent the main process from being
+able to handle the above endpoints.</p>
+<p>In the <code>media_repository</code> worker configuration file, configure the
+<a href="usage/configuration/config_documentation.html#listeners">HTTP listener</a> to
+expose the <code>media</code> resource. For example:</p>
+<pre><code class="language-yaml">worker_app: synapse.app.media_repository
+worker_name: media_worker
+
+worker_listeners:
+  - type: http
+    port: 8085
+    x_forwarded: true
+    resources:
+      - names: [media]
+
+worker_log_config: /etc/matrix-synapse/media-worker-log.yaml
+</code></pre>
+<p>Note that if running multiple media repositories they must be on the same server
+and you must specify a single instance to run the background tasks in the
+<a href="usage/configuration/config_documentation.html#media_instance_running_background_jobs">shared configuration</a>,
+e.g.:</p>
+<pre><code class="language-yaml">media_instance_running_background_jobs: &quot;media-repository-1&quot;
+</code></pre>
+<p>Note that if a reverse proxy is used , then <code>/_matrix/media/</code> must be routed for both inbound client and federation requests (if they are handled separately).</p>
+<h3 id="synapseappuser_dir"><a class="header" href="#synapseappuser_dir"><code>synapse.app.user_dir</code></a></h3>
+<p><strong>Deprecated as of Synapse v1.59.</strong> <a href="#updating-the-user-directory">Use <code>synapse.app.generic_worker</code> with the
+<code>update_user_directory_from_worker</code> option instead.</a></p>
+<p>Handles searches in the user directory. It can handle REST endpoints matching
+the following regular expressions:</p>
+<pre><code>^/_matrix/client/(r0|v3|unstable)/user_directory/search$
+</code></pre>
+<p>When using this worker you must also set <code>update_user_directory: false</code> in the
+shared configuration file to stop the main synapse running background
+jobs related to updating the user directory.</p>
+<p>Above endpoint is not <em>required</em> to be routed to this worker. By default,
+<code>update_user_directory</code> is set to <code>true</code>, which means the main process
+will handle updates. All workers configured with <code>client</code> can handle the above
+endpoint as long as either this worker or the main process are configured to
+handle it, and are online.</p>
+<p>If <code>update_user_directory</code> is set to <code>false</code>, and this worker is not running,
+the above endpoint may give outdated results.</p>
+<h3 id="historical-apps"><a class="header" href="#historical-apps">Historical apps</a></h3>
+<p>The following used to be separate worker application types, but are now
+equivalent to <code>synapse.app.generic_worker</code>:</p>
+<ul>
+<li><code>synapse.app.client_reader</code></li>
+<li><code>synapse.app.event_creator</code></li>
+<li><code>synapse.app.federation_reader</code></li>
+<li><code>synapse.app.federation_sender</code></li>
+<li><code>synapse.app.frontend_proxy</code></li>
+<li><code>synapse.app.pusher</code></li>
+<li><code>synapse.app.synchrotron</code></li>
+</ul>
+<h2 id="migration-from-old-config"><a class="header" href="#migration-from-old-config">Migration from old config</a></h2>
+<p>A main change that has occurred is the merging of worker apps into
+<code>synapse.app.generic_worker</code>. This change is backwards compatible and so no
+changes to the config are required.</p>
+<p>To migrate apps to use <code>synapse.app.generic_worker</code> simply update the
+<code>worker_app</code> option in the worker configs, and where worker are started (e.g.
+in systemd service files, but not required for synctl).</p>
+<h2 id="architectural-diagram"><a class="header" href="#architectural-diagram">Architectural diagram</a></h2>
+<p>The following shows an example setup using Redis and a reverse proxy:</p>
+<pre><code>                     Clients &amp; Federation
+                              |
+                              v
+                        +-----------+
+                        |           |
+                        |  Reverse  |
+                        |  Proxy    |
+                        |           |
+                        +-----------+
+                            | | |
+                            | | | HTTP requests
+        +-------------------+ | +-----------+
+        |                 +---+             |
+        |                 |                 |
+        v                 v                 v
++--------------+  +--------------+  +--------------+  +--------------+
+|   Main       |  |   Generic    |  |   Generic    |  |  Event       |
+|   Process    |  |   Worker 1   |  |   Worker 2   |  |  Persister   |
++--------------+  +--------------+  +--------------+  +--------------+
+      ^    ^          |   ^   |         |   ^   |         |   ^   ^
+      |    |          |   |   |         |   |   |         |   |   |
+      |    |          |   |   |  HTTP   |   |   |         |   |   |
+      |    +----------+&lt;--|---|---------+&lt;--|---|---------+   |   |
+      |                   |   +-------------|--&gt;+-------------+   |
+      |                   |                 |                     |
+      |                   |                 |                     |
+      v                   v                 v                     v
+======================================================================
+                                                         Redis pub/sub channel
+</code></pre>
+
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