This setting defaults to false so the relay host will be used in an MX query so
multiple SMTP servers can be used. gen_smtp code states that all records returned from the
MX query are attempted in order and only a permanent SMTP error will stop the client from
attempting other servers in the list. Connection failures, TLS issues, etc will cause it to
try the next host.
If there is no MX record associated with the relay host, it automatically tries connecting to it
directly.
There is really no reason to expose this to end users. The default value is fine for everyone.
Caching can't work in async tests, so for them it is mocked to a
null cache that is always empty. Synchronous tests are stubbed
with the real Cachex, which is emptied after every test.
Current FedSocket implementation has a bunch of problems. It doesn't
have proper error handling (in case of an error the server just doesn't
respond until the connection is closed, while the client doesn't match
any error messages and just assumes there has been an error after 15s)
and the code is full of bad descisions (see: fetch registry which uses
uuids for no reason and waits for a response by recursively querying a
ets table until the value changes, or double JSON encoding).
Sometime ago I almost completed rewriting fedsockets from scrach to
adress these issues. However, while doing so, I realized that fedsockets
are just too overkill for what they were trying to accomplish, which is
reduce the overhead of federation by not signing every message.
This could be done without reimplementing failure states and endpoint
logic we already have with HTTP by, for example, using TLS cert auth,
or switching to a more performant signature algorithm. I opened
https://git.pleroma.social/pleroma/pleroma/-/issues/2262 for further
discussion on alternatives to fedsockets.
From discussions I had with other Pleroma developers it seems like they
would approve the descision to remove them as well,
therefore I am submitting this patch.
Mark Felder