Notes on SSO logins and media_repository worker (#8701)

If SSO login is used (e.g. SAML) in a multi worker setup, it should be mentioned that currently all SAML logins must run on the same worker, see #7530

Also, if you are using different ports (for example 443 and 8448) in a reverse proxy for client and federation, the path `/_matrix/media` on the client and federation port must point to the listener of the `media_repository` worker, otherwise you'll get a 404 on the federation port for the path `/_matrix/media`, if a remote server is trying to get the media object on federation port, see #8695

changelog.d/8701.doc

@@ -0,0 +1 @@
+Notes on SSO logins and media_repository worker.

docs/workers.md

@@ -262,6 +262,9 @@ using):
 Note that a HTTP listener with `client` and `federation` resources must be
 configured in the `worker_listeners` option in the worker config.
 
+Ensure that all SSO logins go to a single process (usually the main process). 
+For multiple workers not handling the SSO endpoints properly, see
+[#7530](https://github.com/matrix-org/synapse/issues/7530).
 
 #### Load balancing
 
@@ -420,6 +423,8 @@ and you must configure a single instance to run the background tasks, e.g.:
     media_instance_running_background_jobs: "media-repository-1"
 ```
 
+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).
+
 ### `synapse.app.user_dir`
 
 Handles searches in the user directory. It can handle REST endpoints matching