`swarm-controller.service` carried `SetCredential=queue-client.secret:` — an
empty value, which systemd's parser refuses:
/etc/systemd/system/swarm-controller.service:38:
Invalid syntax, ignoring: queue-client.secret:
So the line was dropped on every daemon-reload, and `LoadCredential=` was
fatal again — precisely the failure that default was added to prevent. On a
hive where authelia has not yet minted the secret, the controller refuses to
start rather than coming up with the queue unconfigured.
It looked correct for days because the credential file happened to exist, so
the fail-soft was never exercised.
Measured with `systemd-analyze verify`: an empty value is rejected, any
non-empty one is accepted. The placeholder is a real word rather than filler —
it reaches the token request as the client secret, so authelia refuses it and
the journal names something an operator can act on.
Gate: state/eval-setcredential.sh, with the parent commit as its mutation.
fbb20a56e8