The same Holding as the SNMP poll, for the rest of Steward's own
collectors:
- Monitors: the list is read within 10 s or the last one read stands in;
a start the database doesn't take is kept in memory, so a monitor isn't
checked twice; each result is held and stored at the time it was
checked. A stall shows on the monitors as the checks it saw, not a gap.
- UniFi and Traefik: each poll's writes are held (hold_write) and run
oldest first in one transaction; every reading is stamped with its scrape.
- A held round the database refuses (as opposed to can't be reached) is
stored alone and let go, so it can't hold up every round after it.
The Prometheus scrape is left as it is: its one target, Fabled Archives,
keeps its own database on the same NFS.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The dispatcher ticked once per MONITORS_POLL_INTERVAL and stamped
last_checked_at when the whole batch finished. With a 60 s tick and a 60 s
monitor the next tick saw 59.x s elapsed and skipped, so the monitor ran
every 120 s; a 30 s monitor could never run faster than the tick.
- The dispatcher ticks every 5 s (DISPATCH_TICK_SECONDS) and reads the
monitors and intervals fresh each tick, so a changed interval applies at
the next one.
- Due is measured from the scheduled start, stamped before the check runs,
with half a tick of slack so tick jitter never costs a whole tick. A
long-overdue monitor runs once.
- Each check runs in its own task and records its own result, so a slow
probe holds up nobody; a monitor still being checked is not started
again, and it is freed in a finally.
- A check past CHECK_DEADLINE_SECONDS (120) is recorded down with "Check did
not finish within 120 s" rather than holding its monitor forever.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>