How to Monitor Cron Jobs in Production
Cron jobs are the silent workhorses of your infrastructure. They handle backups, report generation, database cleanup, and email notifications. But when they fail, they often fail silently.
The Problem with Cron Job Monitoring
The problem is that cron itself doesn't have built-in alerting. It just tries to run the command, and if it fails (or doesn't run at all due to a server restart), no one is notified. Unless you're manually checking logs every day, you might not know a critical job has stopped running until it's too late.
Why Cron Jobs Fail Silently
Common Cron Job Failure Modes:
- Script executes but fails partway through
- Dependencies missing or changed
- Disk space exhausted before completion
- Permissions changed, job can't write output
- External service unavailable (API, database)
- Syntax errors in recently modified scripts
- Environment variables missing in cron context
- Path issues (works in terminal, fails in cron)
What to Monitor in Cron Jobs
1. Execution Timing
First, verify that jobs are actually running when scheduled. A misconfigured crontab or a stopped cron service means jobs never execute at all.
2. Execution Results
More importantly, verify that jobs complete successfully. A job can execute on schedule but fail during runtime. Monitor exit codes, error output, and completion status.
3. Execution Duration
Track how long jobs take to complete. Gradually increasing execution time can indicate problems like growing datasets, performance degradation, or resource contention.
Approaches to Cron Job Monitoring
Automated Monitoring Solutions
Modern infrastructure monitoring tools like InfraCaptain automatically detect cron job execution without requiring script modifications. The agent monitors cron daemon logs and job execution, alerting you when jobs fail or miss their schedule.