tellmewhendown

Report from inside your app to TellMeWhenDown — cron heartbeats and self-checks in one line. Zero dependencies (stdlib only), never raises, never slows a request.

pip install tellmewhendown

Put your app's API key (from your app's Setup tab) in the environment:

TMWD_API_KEY=tmwd_...

Heartbeats — "alert me if this stops running"

Call at the end of any scheduled job. If the job dies, the beat stops coming, and that silence is what alerts you.

from tellmewhendown import tmwd

# after your cron job finishes:
tmwd.heartbeat("nightly-backup")

# or decorate the whole job — a raising job sends nothing (which is the point):
@tmwd.beat("nightly-backup")
def run_backup():
    ...

Self-checks — "report what only the app can see"

import time
from tellmewhendown import tmwd

started = time.monotonic()
try:
    db.execute("select 1")
    tmwd.check("db", status="ok", latency_ms=(time.monotonic() - started) * 1000)
except Exception as err:
    tmwd.check("db", status="fail", detail={"error": str(err)})

Two consecutive fail reports open an incident and email you; the next ok resolves it. Monitors register themselves on the first signal — nothing to configure on the dashboard first.

Declare — "alert me even if a job never runs once"

A job that never sends its first signal has no monitor, so its silence is invisible. Declaring registers everything up front, with the real schedule:

# once at startup (idempotent — safe to call every boot):
tmwd.declare([
    {"kind": "heartbeat", "type": "nightly-backup", "interval_seconds": 86400},
    {"kind": "check", "type": "db", "interval_seconds": 3600},
])

Framework notes

• Django: call from management commands, Celery tasks, or a periodic task.
• Flask / FastAPI: call from your scheduled jobs (APScheduler, Celery) or a small health task.
• Anywhere else: it's one POST — see the ingest API docs.

API

from tellmewhendown import TellMeWhenDown

client = TellMeWhenDown(
    api_key="tmwd_...",              # default: os.environ["TMWD_API_KEY"]
    base_url="https://...",          # default: https://ingest.tellmewhendown.com
    timeout=5.0,                     # seconds
    on_error=lambda msg: None,       # observe failures; reporting never raises
)

Every method returns True on success, False on any failure. A failure to report is never allowed to become your app's failure.