What happens when cron jobs overlap?

When cron jobs overlap, multiple instances run simultaneously. This can cause race conditions, database locks, file corruption, memory exhaustion, and inconsistent data.

How do I prevent cron job overlap?

Use lock files (flock), stagger execution times, implement job queues, or use tools like run-one. Monitor job duration to detect when jobs take longer than their interval.

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Cron Overlap Detector

Find cron jobs that run at the same time and could cause conflicts.

crontab -l

$ # Add your cron jobs

$ ANALYSIS_WINDOW

overlap_analysis.log

$ ./detect_overlaps.sh

Jobs

100

Runs/day

Overlaps

DETECTED_OVERLAPS:

⚠️

Potential Conflicts

Jobs running at the same time may compete for resources. Consider using flock or staggering times.

timeline.sh

00:0006:0012:0018:0024:00

Normal

Overlap

Overlaps happen. Know when they do.

CronMonitor tracks execution duration and alerts you when jobs start overlapping.

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Understanding Cron Overlaps

What happens when jobs overlap?

• Race conditions – jobs compete for same data
• Database locks – queries block each other
• Memory exhaustion – instances pile up
• File corruption – concurrent writes

How to prevent overlaps

✓ Use flock for lock files
✓ Stagger execution times
✓ Use job queues
✓ Monitor job duration

Use flock to prevent self-overlap

# Prevent overlap with flock:

*/5 * * * * flock -n /tmp/job.lock /scripts/job.sh

# -n = skip if already running

Cron Overlap Detector

Understanding Cron Overlaps

What happens when jobs overlap?

How to prevent overlaps

Use flock to prevent self-overlap

FAQ

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