health-check

name	health-check
description	System health diagnostics and status checks for infrastructure, services, and dependencies.

Health Check Skill

Overview

Run comprehensive health checks on system infrastructure, services, and dependencies to verify operational status.

Quick Check Commands

Application Health

# Check if application is running
curl -s http://localhost:3000/health | jq .

# Check API response time
time curl -s http://localhost:3000/api/status

Database Health

# PostgreSQL
psql -h localhost -U user -d database -c "SELECT 1;"

# MySQL
mysql -h localhost -u user -p database -e "SELECT 1;"

# Redis
redis-cli ping

Docker Services

# Check running containers
docker ps --format "table {{.Names}}\t{{.Status}}\t{{.Ports}}"

# Check container health
docker inspect --format='{{.State.Health.Status}}' container_name

Node.js Dependencies

# Check for outdated packages
npm outdated

# Audit for vulnerabilities
npm audit

Comprehensive Health Check Script

#!/bin/bash
# health-check.sh

echo "=== System Health Check ==="
echo "Time: $(date)"
echo ""

# 1. Application
echo "## Application"
if curl -sf http://localhost:3000/health > /dev/null; then
    echo "  [OK] Application is responding"
else
    echo "  [FAIL] Application is not responding"
fi

# 2. Database
echo "## Database"
if psql -h localhost -U user -d database -c "SELECT 1;" > /dev/null 2>&1; then
    echo "  [OK] Database is accessible"
else
    echo "  [FAIL] Database is not accessible"
fi

# 3. Redis
echo "## Redis"
if redis-cli ping > /dev/null 2>&1; then
    echo "  [OK] Redis is responding"
else
    echo "  [FAIL] Redis is not responding"
fi

# 4. Disk Space
echo "## Disk Space"
df -h / | tail -1 | awk '{
    if ($5+0 > 90) print "  [WARN] Disk usage: " $5;
    else print "  [OK] Disk usage: " $5
}'

# 5. Memory
echo "## Memory"
free -h | grep Mem | awk '{print "  [INFO] Memory: " $3 " / " $2}'

# 6. Docker (if applicable)
echo "## Docker Services"
if command -v docker &> /dev/null; then
    docker ps --format "  [INFO] {{.Names}}: {{.Status}}" 2>/dev/null || echo "  [WARN] Docker not running"
else
    echo "  [INFO] Docker not installed"
fi

echo ""
echo "=== Health Check Complete ==="

Service-Specific Checks

Web Server (Nginx)

# Check status
systemctl status nginx

# Test configuration
nginx -t

# Check error log
tail -20 /var/log/nginx/error.log

Process Manager (PM2)

# Check all processes
pm2 list

# Check logs
pm2 logs --lines 50

AWS Resources

# Check Lambda function
aws lambda get-function --function-name my-function --query 'Configuration.State'

# Check RDS status
aws rds describe-db-instances --db-instance-identifier my-db --query 'DBInstances[0].DBInstanceStatus'

# Check ECS service
aws ecs describe-services --cluster my-cluster --services my-service --query 'services[0].runningCount'

Monitoring Endpoints

Standard Health Endpoint Response

{
  "status": "healthy",
  "timestamp": "2024-01-15T10:30:00Z",
  "version": "1.2.3",
  "checks": {
    "database": { "status": "healthy", "latency_ms": 5 },
    "redis": { "status": "healthy", "latency_ms": 1 },
    "external_api": { "status": "healthy", "latency_ms": 120 }
  }
}

Implementing Health Endpoint (Node.js)

app.get('/health', async (req, res) => {
  const checks = {
    database: await checkDatabase(),
    redis: await checkRedis(),
  };

  const allHealthy = Object.values(checks).every(c => c.status === 'healthy');

  res.status(allHealthy ? 200 : 503).json({
    status: allHealthy ? 'healthy' : 'unhealthy',
    timestamp: new Date().toISOString(),
    version: process.env.APP_VERSION,
    checks
  });
});

Troubleshooting

Application Not Responding

1. Check if process is running: ps aux | grep node
2. Check port is in use: lsof -i :3000
3. Check logs: pm2 logs or docker logs container

Database Connection Failed

1. Check credentials in .env
2. Verify network connectivity: nc -zv localhost 5432
3. Check max connections: SELECT count(*) FROM pg_stat_activity;

High Memory Usage

1. Identify process: top -o %MEM
2. Check for memory leaks in Node.js: Use --inspect flag
3. Consider restarting service

Disk Space Low

1. Find large files: du -sh /* | sort -rh | head -10
2. Clean logs: journalctl --vacuum-size=100M
3. Remove unused Docker images: docker system prune -a

Alert Thresholds

Metric	Warning	Critical
CPU Usage	> 80%	> 95%
Memory Usage	> 80%	> 95%
Disk Usage	> 80%	> 90%
Response Time	> 500ms	> 2000ms
Error Rate	> 1%	> 5%

Automation

Cron Job for Regular Checks

# Add to crontab: crontab -e
# Run every 5 minutes
*/5 * * * * /path/to/health-check.sh >> /var/log/health-check.log 2>&1

GitHub Actions Health Check

- name: Health Check
  run: |
    curl -sf ${{ env.APP_URL }}/health || exit 1