Silent Cron Failures: Detect Jobs That Fail Without Logging

The Problem: Silent Failures

Cron jobs can fail silently in several ways:

• Script exits with code 0 but doesn't perform its intended work
• Script crashes but error output isn't captured or logged
• Cron daemon stops running, so jobs never execute
• Script runs but hangs indefinitely without producing output
• Permissions change, script fails but cron doesn't report it
• Environment variables missing, script fails silently
• Network timeouts cause silent failures in remote operations

Without explicit success confirmation, you have no way to know if the job actually completed its work.

Solution: Explicit Success Confirmation

Always send an explicit success ping at the end of your script. If the ping doesn't arrive, you know the job failed silently. The ping must be inside your script, not in the cron line, because only the script knows if it completed successfully.

Bash Example: Trap Errors and Always Ping

#!/bin/bash
set -e  # Exit on error
set -o pipefail  # Catch pipe failures

# Your actual work
./backup.sh
./sync.sh

# Single ping at end - if job fails, ping won't arrive and DeadManPing will alert
curl -X POST "https://deadmanping.com/api/ping/backup-daily"

Python Example: Try-Finally for Guaranteed Ping

import requests
import sys

# Your actual work
perform_backup()
sync_data()

# Single ping at end - if job fails, ping won't arrive and DeadManPing will alert
requests.post("https://deadmanping.com/api/ping/backup-daily")

Node.js Example: Process Exit Handlers

const https = require('https');

// Your actual work
async function run() {
  await performBackup();
  await syncData();
  
  // Single ping at end - if job fails, ping won't arrive and DeadManPing will alert
  https.request('https://deadmanping.com/api/ping/backup-daily', { method: 'POST' }).end();
}

run().catch((err) => {
  // If job fails, ping won't arrive - DeadManPing will detect missing ping
  process.exit(1);
});

Verify Cron Daemon is Running

#!/bin/bash
# Check if cron is running before relying on it
# Check if cron is running
CRON_RUNNING=0
if pgrep -x cron > /dev/null || pgrep -x crond > /dev/null; then
  CRON_RUNNING=1
fi

# Single ping with cron status in payload
# In DeadManPing panel: set validation rule "cron_running" == 1
# Panel will automatically detect if cron daemon is not running
curl -X POST "https://deadmanping.com/api/ping/cron-daemon-check?cron_running=$CRON_RUNNING"

Detecting Silent Failures with Dead Man Switch

A dead man switch detects silent failures by monitoring whether your explicit success ping arrives. If the ping doesn't arrive within the expected interval, you know the job failed silently—even if there are no error logs.

This works for all types of silent failures: script crashes, cron daemon stops, permission errors, missing environment variables, and more. As long as your script sends a ping on success, missing pings indicate failures.

Working Examples

See complete, working code examples in our GitHub repository:

Related Articles

Learn more about cron job monitoring and troubleshooting:

• Cron Job Silent Failure Detection

  How to detect silent cron job failures that don't produce error logs.

• Cron Job Failed? How to Detect & Fix in 5 Min

  Step-by-step guide to detect why your cron failed, fix it, and get alerts so it never happens again.

• Monitor Cron Jobs: One Curl Line, No Migration

  Monitor cron jobs with one curl line. No SDK, no migration—get alerts when jobs fail.

• Verify Cron Job Actually Ran

  How to verify that cron jobs actually executed.