The timer thread promoted due work on a fixed one-second tick, so every
delayed item was 0-1000ms late whatever the load — measured on the house
at 705ms mean on a rollershutter stop, which is 2-4% of a 26-second
travel and accumulates in the position the motor node believes it is at.
It now sleeps to the soonest deadline and is woken when a nearer one is
scheduled, which measures 0.9ms end to end through Redis.
A promoted timer also went to the back of the queue. It goes into a due
lane of its own that `claim` reads first, so work that has waited out a
deadline is not held up by work that is merely queued.
Beside it, in the same code: seeding a message now bumps its version, so
a re-put flow's synchronous nodes no longer wait forever on a value that
is sitting in state; the consumer group drops the consumers of engines
that are gone (138 had accumulated on this installation); and the cast
that closes the long-standing `xclaim` mypy error.
stroblme
2c081fe3ed