battery: van-battery daemon (low-charge Pushover alerts + safe shutdown)
While on battery (AC0/online=0), sends escalating Pushover alerts at 25/20/15% and at 10% sends a final alert then `systemctl poweroff` (after shutdown_grace so the alert flushes first). Edge-triggered per discharge episode; re-arms when mains returns; plug-out already-low collapses to a single alert (no burst). Pushover token+user live only in /etc/van-battery/pushover.json (0600), seeded from pushover.json.example on first deploy and never committed. Missing/ placeholder creds disable sending but NOT the shutdown — running flat must always power down safely. Publishes /run/van-battery/state.json. Stdlib only. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Andreas Wrede
co-authored by
Claude Opus 4.8
Claude Opus 4.8
parent
ef6c1ce182
commit
b75b5b16c7
@@ -0,0 +1,218 @@
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#!/usr/bin/env python3
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"""van-battery — battery / mains monitor for the campervan router (wayback).
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While running **off mains** (AC offline, i.e. on battery) it sends escalating
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Pushover alerts as the charge drops past each warn level, and at the shutdown
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level it sends a final alert and powers the machine off cleanly.
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Alerts are edge-triggered per discharge episode: each severity fires once, and
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the whole sequence re-arms when mains power returns. Plug-out already below a
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warn level fires a single alert for the current severity, not a burst.
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Pushover credentials live in a separate 0600 secrets file (see credentials_path),
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never in this repo. Missing/placeholder creds disable sending but NOT the
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shutdown — running flat must always power down safely. Stdlib only.
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"""
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import json
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import os
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import socket
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import subprocess
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import sys
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import time
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import urllib.parse
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import urllib.request
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from datetime import datetime, timezone
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from pathlib import Path
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CONFIG_PATH = os.environ.get("VAN_BATTERY_CONFIG", "/etc/van-battery/config.json")
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STATE_DIR = Path("/run/van-battery")
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STATE_PATH = STATE_DIR / "state.json"
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PSY = Path("/sys/class/power_supply")
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HOST = socket.gethostname()
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DEFAULTS = {
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"poll_interval": 30, # seconds between reads (battery moves slowly)
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"ac_path": "/sys/class/power_supply/AC0/online",
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"battery_path": "/sys/class/power_supply/BAT0",
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"warn_levels": [25, 20, 15], # Pushover alert only
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"shutdown_level": 10, # Pushover alert + poweroff
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"shutdown_grace": 8, # seconds to let the alert flush before poweroff
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"credentials_path": "/etc/van-battery/pushover.json",
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}
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PLACEHOLDERS = {"", "REPLACE_ME", "your-token-here", "your-user-key-here"}
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def log(msg, level="info"):
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pri = {"info": "<6>", "warn": "<4>", "crit": "<2>"}.get(level, "<6>")
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print(pri + msg, flush=True)
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def load_config():
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cfg = dict(DEFAULTS)
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try:
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with open(CONFIG_PATH) as f:
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cfg.update(json.load(f))
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except FileNotFoundError:
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log(f"config {CONFIG_PATH} not found, using built-in defaults")
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except Exception as e:
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log(f"config {CONFIG_PATH} unreadable ({e}), using defaults", "warn")
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return cfg
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def _by_type(kind):
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"""Find a power_supply dir by its `type` (Mains / Battery) — fallback when the
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configured AC0/BAT0 name isn't present on this machine."""
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for d in sorted(PSY.glob("*")):
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try:
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if (d / "type").read_text().strip() == kind:
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return d
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except OSError:
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continue
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return None
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def read_on_battery(cfg):
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"""True if running on battery (mains absent), False if on mains, None if unknown."""
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p = Path(cfg["ac_path"])
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if not p.exists():
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d = _by_type("Mains")
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p = (d / "online") if d else None
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if not p or not p.exists():
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return None
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try:
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return p.read_text().strip() == "0"
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except OSError:
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return None
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def read_capacity(cfg):
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"""Battery charge percentage (int), or None."""
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d = Path(cfg["battery_path"])
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if not (d / "capacity").exists():
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d = _by_type("Battery") or d
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try:
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return int((d / "capacity").read_text().strip())
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except (OSError, ValueError):
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return None
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def load_creds(cfg):
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try:
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c = json.loads(Path(cfg["credentials_path"]).read_text())
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token, user = str(c.get("token", "")).strip(), str(c.get("user", "")).strip()
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if token in PLACEHOLDERS or user in PLACEHOLDERS:
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return None
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return token, user
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except FileNotFoundError:
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return None
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except Exception as e:
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log(f"credentials {cfg['credentials_path']} unreadable ({e})", "warn")
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return None
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def pushover(cfg, title, message, priority=0):
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creds = load_creds(cfg)
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if not creds:
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log(f"pushover skipped (no credentials): {title} — {message}", "warn")
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return False
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token, user = creds
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data = urllib.parse.urlencode({
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"token": token, "user": user, "title": title,
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"message": message, "priority": priority,
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}).encode()
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req = urllib.request.Request("https://api.pushover.net/1/messages.json", data=data)
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try:
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with urllib.request.urlopen(req, timeout=10) as resp:
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ok = resp.status == 200
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if not ok:
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log(f"pushover HTTP {resp.status}", "warn")
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return ok
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except Exception as e:
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log(f"pushover send failed: {e}", "warn")
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return False
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def severity(cap, levels):
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"""Most-severe (lowest) threshold the capacity has reached, or None if above all.
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levels: thresholds sorted ascending. cap=12, levels=[10,15,20,25] -> 15."""
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reached = [t for t in levels if cap <= t]
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return min(reached) if reached else None
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def poweroff(cfg):
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log("shutdown level reached — powering off", "crit")
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time.sleep(cfg["shutdown_grace"]) # give the Pushover POST time to land first
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try:
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subprocess.run(["systemctl", "poweroff"], check=False)
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except Exception as e:
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log(f"poweroff failed: {e}", "crit")
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def write_state(on_batt, cap, armed):
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STATE_DIR.mkdir(parents=True, exist_ok=True)
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payload = {
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"updated": datetime.now(timezone.utc).isoformat(timespec="seconds"),
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"on_battery": on_batt,
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"capacity": cap,
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"alerted_below": armed, # lowest level alerted this discharge episode, or null
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}
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tmp = STATE_PATH.with_suffix(".tmp")
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tmp.write_text(json.dumps(payload))
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tmp.replace(STATE_PATH)
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def main():
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cfg = load_config()
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levels = sorted(cfg["warn_levels"] + [cfg["shutdown_level"]])
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shutdown_level = cfg["shutdown_level"]
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last_alerted = None # lowest threshold alerted in the current discharge episode
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shutdown_issued = False
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prev_on_batt = None
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log(f"van-battery up: poll {cfg['poll_interval']}s, warn {cfg['warn_levels']}, "
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f"shutdown {shutdown_level}%")
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while True:
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on_batt = read_on_battery(cfg)
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cap = read_capacity(cfg)
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if on_batt is False:
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# On mains: re-arm the whole sequence for the next discharge episode.
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if prev_on_batt:
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log("mains restored — alerts re-armed")
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last_alerted = None
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shutdown_issued = False
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elif on_batt is True and cap is not None:
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if prev_on_batt is False:
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log(f"mains lost — running on battery at {cap}%", "warn")
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sev = severity(cap, levels)
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if sev is not None and (last_alerted is None or sev < last_alerted):
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last_alerted = sev
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is_shutdown = sev <= shutdown_level
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if is_shutdown:
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pushover(cfg, f"⚠ {HOST}: battery {cap}% — shutting down",
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f"On battery at {cap}% (≤{shutdown_level}%). Powering off now to "
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f"protect the system.", priority=1)
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if not shutdown_issued:
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shutdown_issued = True
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poweroff(cfg)
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else:
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log(f"battery {cap}% on battery — alerting (level {sev})", "warn")
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pushover(cfg, f"{HOST}: battery {cap}%",
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f"Running on battery, charge down to {cap}% (alert at {sev}%). "
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f"Shutdown at {shutdown_level}%.")
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prev_on_batt = on_batt
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try:
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write_state(on_batt, cap, last_alerted)
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except OSError as e:
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log(f"state write failed: {e}", "warn")
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time.sleep(cfg["poll_interval"])
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if __name__ == "__main__":
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try:
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main()
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except KeyboardInterrupt:
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sys.exit(0)
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