liauw-media/skills/safety/resource-limiting

Resource Limiting Skill

Protect shared servers from resource exhaustion during development tasks.

When to Use

• Running tests on a server that hosts other sites
• Running migrations on a shared database server
• Running any CPU/RAM intensive task on production/staging
• When you notice server becoming unresponsive during tasks

The Problem

Development tasks like tests, builds, and migrations can consume 100% CPU/RAM, causing:

• Other websites on the server to stop responding
• SSH connections to hang
• Database connections to time out
• Server to become unreachable until task finishes

Solution: Resource Limiting

Quick Commands

For tests (recommended):

nice -n 19 ionice -c 3 vendor/bin/pest --processes=1
nice -n 19 ionice -c 3 npm test
nice -n 19 ionice -c 3 pytest

For any heavy command:

nice -n 19 ionice -c 3 <your-command>

Tools

| Tool | Built-in? | What it Does | |------|-----------|--------------| | nice -n 19 | Yes | Lowest CPU priority - other processes get CPU first | | ionice -c 3 | Yes | Lowest I/O priority - other processes get disk first | | cpulimit -l 50 | No | Hard limit to 50% CPU (install: apt install cpulimit) | | --processes=1 | N/A | Disable parallel testing |

By Task Type

Running Tests

# Best for shared servers
nice -n 19 ionice -c 3 vendor/bin/pest --processes=1

# If you have cpulimit installed
cpulimit -l 50 -- vendor/bin/pest

Running Migrations

nice -n 19 php artisan migrate
nice -n 19 python manage.py migrate

Running Builds

nice -n 19 npm run build
nice -n 19 composer install

Running Heavy Scripts

nice -n 19 ionice -c 3 php artisan queue:work --once

Advanced: systemd Resource Control

For Linux servers with systemd:

# Limit to 50% CPU and 1GB RAM
systemd-run --scope -p CPUQuota=50% -p MemoryMax=1G vendor/bin/pest

# Limit to 25% CPU and 512MB RAM
systemd-run --scope -p CPUQuota=25% -p MemoryMax=512M npm test

Detection: Is This a Shared Server?

# Check for web servers
pgrep nginx && echo "Nginx running - shared server likely"
pgrep apache2 && echo "Apache running - shared server likely"
pgrep mysql && echo "MySQL running - shared server likely"

# Check for other PHP processes
pgrep -c php-fpm && echo "PHP-FPM running - shared server"

Rule: If web servers are running, use resource limits.

Checklist

Before running heavy tasks on shared servers:

• [ ] Check if this is a shared/production server
• [ ] Use nice -n 19 for CPU priority
• [ ] Use ionice -c 3 for disk I/O priority
• [ ] Use --processes=1 to disable parallel execution
• [ ] Consider running in CI/CD instead of on server

Best Practice

Add to your project's CLAUDE.md:

## Server Environment

This is a shared server hosting multiple sites.
ALWAYS use resource limits when running tests or heavy tasks:

```bash
nice -n 19 ionice -c 3 vendor/bin/pest --processes=1

## Related Skills

- `database-backup` - Backup before heavy operations
- `defense-in-depth` - Multiple safety layers