Get rid of `worker_main_http_uri`

[richvdh]

worker_main_http_uri is used in exactly one place (the handler for keys/upload/) to proxy requests through to the main process. Given we already have the "http replication listener", this is needlessly confusing and annoying to configure.

[realtyem]

I think I tracked down all the information to give this a shot.

• Looks like the worker_main_http_uri object in the WorkerConfig class is populated from the worker.yaml file at line 158 in workers.py and then pulled into the KeyUploadServlet() class in generic_worker.py at line 148 as self.main_uri. I think from there it gets processed in the same file(I could find no other references to this variable) as part of post_json_get_json() where the rest of the (ascii)string for the uri is appended to the request being sent.
• The values needed would be
  • scheme to determine if 'http' or 'https' would be appropriate. I think this can gotten from config.server.listeners[1].tls. I think I would have to iterate over all listeners in this section to find the one with a client resource. I would need to use this same listener below for port.
  • netloc to identify if an IP address or hostname is declared. I think I can get this from config.workers.worker_replication_host as it should be the same value and be pointing at the homeserver's IP address or hostname(as appropriate).
  • port to make sure it's pointed at the actual client port and not something else. I think I can get this from the same listener I found for scheme and get it from hs.config.server.listeners[1].port.

I believe it's a simple string concatenation to put the pieces together and set it either at worker_main_http_uri in workers.py(referenced above) or factor the config value out altogether and set it in the KeyUploadServlet()(again, referenced above) directly. I know which one I would choose.

Does that sound about right? Did I miss anything obvious, easier or a better way?

[richvdh]

There are lots of other bits of worker<->worker communication that work via the "http replication API": see the servlets in https://github.com/matrix-org/synapse/blob/15bdb0da522ba902e6a1c55f7f6775faeb47176a/synapse/replication/http. We should use something similar for uploading keys.

[realtyem]

I'm sorry, for the moment that kind of thing is beyond me.