A message received via inter-node transfer, on systems hosted on AWS, could
end up with a wildly incorrect far-future timestamp. The underlying mac_address
crate would pick a NIC with the same MAC address as other AWS instances in the
cluster, and that triggered a code path where the collision resolving logic
misinterpreted the timestamp portion of the incoming spool id.
The thing that made this painful was the logic in spool_id.rs: it
misinterpreted the subsecond portion of the timestamp extracted from
the uuid, and due to the way that that field wraps, could produce wildly
inaccurate deltas with a huge multiplier.
As a belt and suspenders treatment, allow the user to influence which
MAC address is selected via the new KUMO_MAC_INTERFACE and
KUMO_MAC_ADDRESS environment variables.
Wez Furlong
Mike Hillyer