mc-webui/docs/watchdog.md

Container Watchdog

The Container Watchdog is a systemd service that monitors Docker containers and automatically restarts unhealthy or stopped ones. This is useful for ensuring reliability, especially on resource-constrained systems.

Features

• Health monitoring - Checks container status every 30 seconds
• Automatic restart - Restarts containers that become unhealthy
• Auto-start stopped containers - Starts containers that have stopped (configurable)
• Diagnostic logging - Captures container logs before restart for troubleshooting
• HTTP status endpoint - Query container status via HTTP API
• Restart history - Tracks all automatic restarts with timestamps

Installation

cd ~/mc-webui
sudo ./scripts/watchdog/install.sh

The installer will:

• Create a systemd service mc-webui-watchdog
• Start monitoring containers immediately
• Enable automatic startup on boot
• Create log file at /var/log/mc-webui-watchdog.log

Usage

Check service status

systemctl status mc-webui-watchdog

View watchdog logs

# Real-time logs
tail -f /var/log/mc-webui-watchdog.log

# Or via journalctl
journalctl -u mc-webui-watchdog -f

HTTP Status Endpoints

The watchdog provides HTTP endpoints on port 5051:

# Service health
curl http://localhost:5051/health

# Container status
curl http://localhost:5051/status

# Restart history
curl http://localhost:5051/history

Diagnostic Files

When a container is restarted, diagnostic information is saved to:

/tmp/mc-webui-watchdog-{container}-{timestamp}.log

These files contain:

• Container status at the time of failure
• Recent container logs (last 200 lines)
• Timestamp and restart result

Configuration (Optional)

No configuration required - the installer automatically detects paths and sets sensible defaults.

If you need to customize the behavior, the service supports these environment variables:

Variable	Default	Description
MCWEBUI_DIR	(auto-detected)	Path to mc-webui directory
CHECK_INTERVAL	30	Seconds between health checks
LOG_FILE	/var/log/mc-webui-watchdog.log	Path to log file
HTTP_PORT	5051	HTTP status port (0 to disable)
AUTO_START	true	Start stopped containers (set to false to disable)

To modify defaults, create an override file:

sudo systemctl edit mc-webui-watchdog

Then add your overrides, for example:

[Service]
Environment=CHECK_INTERVAL=60
Environment=AUTO_START=false

Uninstall

sudo ~/mc-webui/scripts/watchdog/install.sh --uninstall

Note: The log file is preserved after uninstall. Remove manually if needed:

sudo rm /var/log/mc-webui-watchdog.log

Troubleshooting

Service won't start

Check the logs:

journalctl -u mc-webui-watchdog -n 50

Common issues:

• Docker not running
• Python 3 not installed
• Permission issues

Containers keep restarting

Check the diagnostic files in /tmp/mc-webui-watchdog-*.log to see what's causing the containers to become unhealthy.

HTTP endpoint not responding

Verify the service is running and check if port 5051 is available:

systemctl status mc-webui-watchdog
ss -tlnp | grep 5051