Archived
jschoubben
0d975a051d
`status` hung. It composes a declaration for every node to answer *is this machine running what I would send it*, and composing one assigns each module a machine port — so the question wrote to the database, and wrote to the same rows as the machine it was asking about. `port_assignment` is unique on (node, machine). Two transactions inserting the same port do not race, they queue: the second waits on the index until the first commits. A status polled every two seconds while a node applies is two writers on those rows, and the poll stopped returning rather than returning something wrong — which is the better failure of the two, and still a failure. The latent version of this was there before anything polled: two compositions running at once could both allocate. So allocation belongs to the send path alone. The mesh chooses a port when it commits to sending one; every other caller reads what was chosen. A module with nothing assigned has never been sent, which is precisely what "waiting" means — the read needs no number to be right about that, and inventing one would make the answer worse. Named rather than passed as a bare bool: at three call sites, `true` and `false` say nothing about which of these two things is meant. Checked by the lab, which now polls status throughout an apply.