Digital Ocean droplets, specially Wordpress sites are low-memory VPS instances. As result, they frequently crash due to Out of Memory (OOM) errors. This guide explains how to diagnose OOM crashes, configure Apache for limited resources, and implement automated recovery.
Diagnosing OOM Issues
Check system logs for OOM killer activity:
sudo journalctl --since "7 days ago" | grep -i "out of memory\|oom\|killed"
# Look for entries like:
Sep 23 06:52:13 server systemd[1]: system.slice: A process of this unit has been killed by the OOM killer.
Check Apache service status:
systemctl status apache2`
If the output shows Result: oom-kill, Apache was terminated by the OOM killer.
Check current memory usage
free -h
df -h
How to Configure Apache for Low-Memory Servers
The default Apache configuration often allows too many concurrent processes for budget VPS instances.
Modify MPM Prefork Settings
sudo nano /etc/apache2/mods-available/mpm_prefork.conf
Replace the content with optimized settings for 1GB RAM:
<IfModule mpm_prefork_module>
StartServers 2
MinSpareServers 2
MaxSpareServers 5
MaxRequestWorkers 15
MaxConnectionsPerChild 1000
</IfModule>
Apply changes:
sudo systemctl reload apache2
How to Add Swap Space
Swap space acts as emergency memory when physical RAM is exhausted. Without swap, the OOM killer immediately terminates processes when memory runs out. With swap configured, the system can temporarily use disk space as memory, preventing sudden process termination and allowing time for automatic recovery.
Create and enable a 2GB swap file:
sudo fallocate -l 2G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
Make swap permanent:
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
Verify swap is active:
free -h
How to Implement Automated Recovery
The monitoring script provides:
- Service health monitoring
- Automatic service restart
- Memory usage alerts
- Email notifications via Resend API
- Website response testing
Installation Steps
Download and save the script:
sudo nano /usr/local/bin/service-monitor.sh
Configure email settings in the script:
RESEND_API_KEY="your_api_key_here"
FROM_EMAIL="[email protected]"
TO_EMAIL="[email protected]"
SERVER_NAME="production-server"
Make it executable:
sudo chmod +x /usr/local/bin/service-monitor.sh
Test the script:
sudo /usr/local/bin/service-monitor.sh
cat /var/log/service-monitor.log
Schedule with cron (runs every 5 minutes):
sudo crontab -e
Add this line:
*/5 * * * * /usr/local/bin/service-monitor.sh
Email Alert Configuration
The script uses Resend API for email notifications. Get an API key from resend.com and update the configuration variables.
The script sends alerts for:
- Apache service failures
- Website unresponsive
- High memory usage (>85%)
- Service recovery confirmations
Results
This configuration typically reduces memory usage from 90%+ to 35-60% and eliminates OOM crashes. The monitoring script provides automatic recovery within 30 seconds of detecting issues.
The approach prevents extended downtime by addressing both the root cause (excessive Apache processes) and implementing proactive monitoring with automated remediation.