Constrain profile endpoint handling to profile_updates writer workers

And update relevant documentation/integration test config.

docker/complement/conf/start_for_complement.sh

@@ -60,12 +60,13 @@ if [[ -n "$SYNAPSE_COMPLEMENT_USE_WORKERS" ]]; then
       federation_inbound, \
       federation_reader, \
       federation_sender, \
+      profile_updates, \
       synchrotron, \
       client_reader, \
       appservice, \
       pusher, \
       device_lists:2, \
-      stream_writers=account_data+presence+receipts+to_device+typing"
+      stream_writers=account_data+presence+profile_updates+receipts+to_device+typing"
 
   fi
   log "Workers requested: $SYNAPSE_WORKER_TYPES"

docker/configure_workers_and_start.py

@@ -308,6 +308,15 @@ WORKERS_CONFIG: dict[str, dict[str, Any]] = {
         "shared_extra_conf": {},
         "worker_extra_conf": "",
     },
+    "profile_updates": {
+        "app": "synapse.app.generic_worker",
+        "listener_resources": ["client", "replication"],
+        "endpoint_patterns": [
+            "^/_matrix/client/(unstable/uk.tcpip.msc4133|api/v1|r0|v3|unstable)/profile/.*/"
+        ],
+        "shared_extra_conf": {},
+        "worker_extra_conf": "",
+    },
     "device_lists": {
         "app": "synapse.app.generic_worker",
         "listener_resources": ["client", "replication"],
@@ -517,6 +526,7 @@ def add_worker_roles_to_shared_config(
         "typing",
         "push_rules",
         "thread_subscriptions",
+        "profile_updates",
     }
 
     # Worker-type specific sharding config. Now a single worker can fulfill multiple

docs/upgrade.md

@@ -117,6 +117,34 @@ each upgrade are complete before moving on to the next upgrade, to avoid
 stacking them up. You can monitor the currently running background updates with
 [the Admin API](usage/administration/admin_api/background_updates.html#status).
 
+# Upgrading to v1.151.0
+
+## Profile Updates Stream Writer Workers
+
+This version of Synapse adds a new `profile_updates` writer stream. The
+following endpoints may now only be handled by either the main process, or a
+worker that is designed a "profile_updates" writer. If you are already routing
+the following endpoints to a worker:
+
+```
+/_matrix/client/(api/v1|r0|v3)/profile/<user_id>/(<field_name>?)
+/_matrix/client/unstable/uk.tcpip.msc4133/profile/<user_id>/(<field_name>?)
+```
+
+those worker(s) need to be marked as a stream writer for the `profile_updates`
+stream in the shared config, using the
+[`stream_writers`](https://element-hq.github.io/synapse/v1.151/usage/configuration/config_documentation.html#stream_writers)
+config option:
+
+```yaml
+stream_writers:
+    profile_updates: worker1
+```
+
+as well as included in the
+[`instance_map`](https://element-hq.github.io/synapse/v1.151/usage/configuration/config_documentation.html#instance_map)
+config option.
+
 # Upgrading to v1.150.0
 
 ## Removal of the `systemd` pip extra

docs/usage/configuration/config_documentation.md

@@ -4475,6 +4475,8 @@ This setting has the following sub-options:
 
 * `device_lists` (string): Name of a worker assigned to the `device_lists` stream.
 
+* `profile_updates` (string): Name of a worker assigned to the `profile_updates` stream.
+
 Example configuration:
 ```yaml
 stream_writers:

schema/synapse-config.schema.yaml

@@ -5522,6 +5522,9 @@ properties:
       device_lists:
         type: string
         description: Name of a worker assigned to the `device_lists` stream.
+      profile_updates:
+        type: string
+        description: Name of a worker assigned to the `profile_updates` stream.
     default: {}
     examples:
       - events: worker1

synapse/rest/client/profile.py

@@ -284,8 +284,17 @@ class UnstableProfileFieldRestServlet(ProfileFieldRestServlet):
 
 
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
-    # The specific field endpoint *must* appear before the generic profile endpoint.
-    ProfileFieldRestServlet(hs).register(http_server)
+    # Updating user profiles requires the ability to write to the
+    # `profile_updates` stream.
+    if hs.get_instance_name() in hs.config.worker.writers.profile_updates:
+        # The specific field endpoint *must* appear before the generic profile
+        # endpoint (below).
+
+        # TODO: Is it possible to still allow any generic_worker to handle the
+        # `GET` endpoint?
+        ProfileFieldRestServlet(hs).register(http_server)
+
+        if hs.config.experimental.msc4133_enabled:
+            UnstableProfileFieldRestServlet(hs).register(http_server)
+
     ProfileRestServlet(hs).register(http_server)
-    if hs.config.experimental.msc4133_enabled:
-        UnstableProfileFieldRestServlet(hs).register(http_server)