frontend_proxy worker claims it forwards requests to the main process, but it doesn't

[turt2live]

Having ensured I set up the worker_main_http_uri to point to the main process, making a request to something like /_matrix/client/versions results in a 400 unrecognized request. There's no evidence that it actually tries to contact the main process (no additional logging in the worker or main process)

[erikjohnston]

The frontend proxy only proxies certain paths: https://github.com/matrix-org/synapse/blob/master/docs/workers.rst#synapseappfrontend_proxy, which does not include /_matrix/client/versions

[erikjohnston]

Oh, the docs are wrong:

It will proxy any requests it cannot handle to the main synapse instance. It must therefore be configured with the location of the main instance, via the worker_main_http_uri setting in the frontend_proxy worker configuration file.