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perf: monitor caches run state, ~halving live-feed latency

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Each monitor poll was sending DOD? + Measure? (two commands), and the NL43
enforces >=1s between commands, so updates were ~2.5s apart. The run state
changes rarely, so cache it and refresh via Measure? only every
MONITOR_STATE_REFRESH_S (default 30s); most polls now send just DOD? (one
rate-limited command) -> ~1.3s/update. Also trim MONITOR_POLL_INTERVAL to
0.25s since the device rate-limit is the real pacer.

request_dod() gains an optional measurement_state arg: when supplied it
reuses that state and skips the Measure? round-trip; None preserves the old
query-every-time behavior.

~1Hz is the device floor for DOD (the >=1s command spacing); DRD's 10Hz
push isn't reachable via polling, but ~1s is a normal cadence for SLM levels.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
serversdown
2026-06-09 18:52:13 +00:00
parent 87c06f1519
commit 9d34779171
2 changed files with 35 additions and 12 deletions
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app/monitor.py
+22 -4
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@@ -27,9 +27,14 @@ from app.alerts import alert_evaluator
logger = logging.getLogger(__name__)
# Sleep between DOD polls. Note the 1s device rate-limit (and DOD?+Measure? per
# poll) already paces the effective rate to a few seconds; this is the extra idle.
MONITOR_POLL_INTERVAL = float(os.getenv("MONITOR_POLL_INTERVAL", "1.0"))
# Extra idle between DOD polls. The 1s device rate-limit already paces consecutive
# DOD? commands, so this just needs to be small — the rate-limit is the real floor.
MONITOR_POLL_INTERVAL = float(os.getenv("MONITOR_POLL_INTERVAL", "0.25"))
# How often to refresh the run state (Measure?). It changes rarely, so we cache it
# and skip that second rate-limited command on most polls — roughly halving the
# per-update latency (~2.5s -> ~1.3s).
MONITOR_STATE_REFRESH_S = float(os.getenv("MONITOR_STATE_REFRESH_S", "30"))
# If nothing has been broadcast in this many seconds (e.g. device offline and
# silent), send a keepalive frame so reverse proxies don't drop the idle WS.
@@ -70,6 +75,8 @@ class DeviceMonitor:
self._last_payload: Optional[dict] = None # replayed to new subscribers
self._consec_fail = 0
self._reachable = True # last broadcast reachability (for transition frames)
self._cached_state: Optional[str] = None # run state, refreshed periodically
self._last_state_refresh = 0.0
@property
def running(self) -> bool:
@@ -168,7 +175,18 @@ class DeviceMonitor:
ftp_username=cfg.ftp_username, ftp_password=cfg.ftp_password,
ftp_port=cfg.ftp_port or 21,
)
snap = await client.request_dod()
# Refresh the run state only every MONITOR_STATE_REFRESH_S; reuse the
# cached state otherwise so most polls send just DOD? (one rate-limited
# command) instead of DOD? + Measure?.
now = asyncio.get_running_loop().time()
refresh_state = (self._cached_state is None
or now - self._last_state_refresh >= MONITOR_STATE_REFRESH_S)
snap = await client.request_dod(
measurement_state=None if refresh_state else self._cached_state
)
if refresh_state:
self._cached_state = snap.measurement_state
self._last_state_refresh = now
snap.unit_id = self.unit_id
persist_snapshot(snap, db)
db.commit()