Features

• Monitors hosts from /etc/hosts file

• Checks reachability via ping (falls back to ARP)

• Exports Prometheus metrics for Node Exporter textfile collector

• Environment-based configuration

• Proper error handling and logging

• Cross-platform support (Linux, macOS, Windows)

• Python 3.9+ with type hints

Installation

From PyPI:

pip install hosts-monitoring

From source:

git clone https://github.com/blasebast/hosts_monitoring
cd hosts_monitoring
pip install -e .

Quick Start

Basic usage:

# Copy configuration template
cp .env.example .env

# Edit configuration
nano .env

# Run monitoring
hosts-monitoring

Monitor single host:

hosts-monitoring -hostname 192.168.1.1

Docker usage:

docker-compose up -d

Configuration

Configure via environment variables in .env file:

• HOSTS_FILE - Path to hosts file (default: /etc/hosts)

• OUTPUT_DIR - Output directory for metrics (default: /var/lib/node_exporter/textfile_collector)

• OUTPUT_FILE_BASE - Output filename (default: node_network_hosts_up.prom)

• PING_TIMEOUT - Ping timeout in seconds (default: 1)

• LOG_DIR - Log directory (default: /tmp)

• ARP_CMD - Path to arp command (default: /usr/sbin/arp)

• LOG_LEVEL - Logging level (default: INFO)

Docker

Using docker-compose (recommended):

docker-compose up -d

Using Docker image directly:

docker build -t hosts-monitoring .
docker run --rm \
  -v /etc/hosts:/etc/hosts:ro \
  -v /var/lib/node_exporter/textfile_collector:/metrics \
  -e HOSTS_FILE=/etc/hosts \
  -e OUTPUT_DIR=/metrics \
  hosts-monitoring

Integration with Prometheus

Add to prometheus.yml:

scrape_configs:
  - job_name: 'node'
    static_configs:
      - targets: ['localhost:9100']

The node_network_hosts_up metric will be collected via Node Exporter’s textfile collector.

Metrics

Metric name: node_network_hosts_up

Labels: - hostname: Hostname from /etc/hosts

Values: - 1: Host is reachable (ping or ARP success) - 0: Host is unreachable

Example output:

node_network_hosts_up{hostname="router"} 1
node_network_hosts_up{hostname="server"} 1
node_network_hosts_up{hostname="offline-host"} 0

Running as Cron Job

Add to crontab to run every minute:

* * * * * /usr/local/bin/hosts-monitoring

Or with custom configuration:

* * * * * source /etc/hosts-monitoring/.env && hosts-monitoring

Development

Setup development environment:

pip install -e ".[dev]"
pytest

Run tests:

pytest tests/
pytest --cov=hmon tests/

Troubleshooting

“Output directory doesn’t exist” - Ensure output directory exists and is writable - Usually /var/lib/node_exporter/textfile_collector for Node Exporter

“Hosts file not found” - Check HOSTS_FILE environment variable - Default is /etc/hosts on Linux/macOS - Windows: typically C:\Windows\System32\drivers\etc\hosts

“ARP command not found” - ARP checking is optional and will be skipped if unavailable - Ping will still be used for reachability checks

“Permission denied” writing metrics - Container/process needs write permissions to output directory - In docker-compose, metrics directory is volume-mounted - For manual setup: chmod 777 /var/lib/node_exporter/textfile_collector

Performance

• Default ping timeout: 1 second (configurable via PING_TIMEOUT)

• Falls back to ARP if ping fails

• Metrics written atomically (temp file + rename)

• Suitable for cron execution every 1-5 minutes

License

GNU General Public License v3.0 - See LICENSE file

Contributing

Contributions welcome! Please:

1. Fork the repository

2. Create a feature branch

3. Add tests for new functionality

4. Ensure tests pass: pytest

5. Submit a pull request

Author

Sebastian Blasiak - https://github.com/blasebast