A CPU spike occurs when processor usage suddenly rises, slowing or blocking the entire server. Here's how to identify the cause and resolve the problem.
Symptoms
- Response time that suddenly explodes
- Load average higher than CPU count
- Slow SSH connections or timeout
- 503 errors or timeouts on user side
Common Causes
- Poorly optimized script: An infinite loop or O(n²) algorithm on large data.
- Attack or bot: A bot crawling aggressively or a DDoS attack.
- Concurrent cron: Multiple instances of the same cron running in parallel.
Diagnostic Steps
- Identify the process with htop or top
- Check Apache/Nginx logs for abnormal traffic
- Examine running crons (ps aux | grep cron)
- Analyze MySQL queries (SHOW PROCESSLIST)
Automate with MoniTao
MoniTao detects CPU spike effects:
- Alerts on abnormal response times
- Detection of 503 errors and timeouts
- History to correlate with your deployments
Best Practices
- Limit cron resources (nice, cpulimit)
- Use a rate limiter against abuse
- Implement a lock to avoid concurrent crons
- Monitor load average, not just CPU%
FAQ
What's the difference between CPU% and load average?
CPU% measures instantaneous usage. Load average measures average load (including I/O).
How to limit script resources?
Use nice for priority and cpulimit for a strict cap.
Does horizontal scaling solve the problem?
It distributes load but doesn't fix a poorly optimized script.
Can MoniTao measure CPU?
Not directly, but response times and 503 errors reveal problems.
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