Why `exit code 0` is lying to you

Source: Dev.to

The problem with “did it run?”

Your cron job ran at 2 am. The exit code was 0. Everything’s fine, right?

Last month, my SIRENE data import script ran successfully every Sunday for 3 weeks straight. Exit code 0. No errors in the logs. Green across the board.

Except it was importing 0 rows instead of 16.8 million. Nobody noticed for 3 weeks.

Most cron‑monitoring tools answer one question: did the job execute?
They use a dead‑man’s switch — your script pings a URL when it finishes, and if the ping doesn’t arrive, you get an alert.

That’s useful, but it misses the most dangerous failure mode: the job runs successfully but produces garbage.

• Your backup script runs but the database connection silently fails → 0 bytes backed up
• Your ETL job processes 12 rows instead of 14 000 → exit code 0
• Your import takes 45 minutes instead of 2 → no error, just slow degradation

Exit code 0 doesn’t mean “everything is fine.” It means “I didn’t crash.”

What if your monitoring could understand the output?

I built Crontiq to answer a different question: did it run and was the output normal?

The idea is simple. Instead of just pinging a URL, you send your job’s output as JSON:

# At the end of your script:
curl -X POST https://ping.crontiq.io/p/$API_KEY/import-sirene \
  -H "Content-Type: application/json" \
  -d "{\"rows\": $ROW_COUNT, \"duration_ms\": $DURATION, \"errors\": $ERROR_COUNT}"

Crontiq does three things automatically:

1. Extracts every numeric value from your JSON (including nested objects, e.g. {"db": {"rows": 100}} → db.rows = 100).
2. Tracks each metric over time with sparkline graphs.
3. Detects anomalies using a moving‑average + 2 standard deviations.

No configuration, no thresholds to set, no schema to define. Just send JSON and it figures it out.

The math is embarrassingly simple

The anomaly detection isn’t machine learning or anything fancy. It’s a moving average over the last 10 values, plus 2 standard deviations:

average = avg(last_10_values)
stddev  = stddev(last_10_values)
is_anomaly = abs(current_value - average) > 2 * stddev

If your rows metric usually hovers around 16,800,000 and suddenly drops to 0, that’s a deviation of ~7,200 standard deviations → you get an alert.

If it gradually decreases from 16.8 M to 16.7 M over a few weeks, nothing happens — that’s within the normal range.

Healthchecks.io stores your POST body as raw text. Cronitor requires you to format metrics in a specific query‑parameter syntax (&metric=count:3329). With Crontiq, you just send whatever JSON your script already produces.

The badge that sells itself

When you make a monitor public, Crontiq generates a live SVG badge:

[![SIRENE Import](https://crontiq.io/badge/cq_chk_xxx.svg)](https://crontiq.io/public/cq_chk_xxx)

The badge shows actual data, not just “passing” or “failing”:

import-sirene | 16.8M rows | ✓ healthy

Put it in your GitHub README and every visitor sees proof that your data pipeline is running and healthy. Clicking the badge opens a public status page with sparklines and history.

Examples

• GEOREFER examples – monitors a 16.8 M‑row French business database
• GreenCalc examples – monitors a carbon‑footprint API

How it’s built

The stack is straightforward:

• Java 21 / Spring Boot 3.3 – handles the ping ingestion
• PostgreSQL with partitioned tables – stores pings and metrics by month
• Redis – caches monitor status for fast badge generation
• Hetzner – single server, Docker containers

The ping endpoint responds in under 50 ms. JSON parsing, metric extraction, and anomaly detection happen asynchronously, so your script never waits for Crontiq to finish.

JSON flattening is recursive – any nested structure becomes dot‑notation keys:

{
  "db": {
    "connections": 5,
    "pool_size": 20
  },
  "rows": 14209
}

becomes:

• db.connections = 5
• db.pool_size = 20
• rows = 14209

Each key gets its own sparkline on the dashboard.

Free. Actually free.

Crontiq is the free front door to the AZMORIS developer ecosystem: 20 monitors, unlimited pings, auto‑metrics, email alerts — no credit card, no trial period.

Why free? Because it was built to solve my own problem first (monitoring my own APIs), and a good loss leader brings more value than a paywall.

Try it: crontiq.io

Crontiq is part of the AZMORIS ecosystem, which includes GEOREFER (French business data API), Doxnex (document intelligence), GreenCalc (carbon‑footprint API), and IDonex (identity management).