Link Monitor

A Rust-based internet connectivity monitoring tool that periodically checks specified URLs and logs outages and recoveries.

Project Purpose

This tool monitors internet connectivity by sending HTTP GET requests to configured target URLs. It logs the status of each target and detects internet outages based on configurable failure thresholds.

Configuration

The project uses a config.toml file to configure its behavior. Key configuration options include:

• log_file: Path to the log file where monitoring logs are saved.
• log_to_console: A boolean (true or false) to enable or disable logging to the console.
• check_interval_seconds: Interval in seconds between each round of checks.
• max_retries: Number of retry attempts for each target after the first request before considering it failed. Each target is requested up to max_retries + 1 times; 0 means a single request with no retries.
• failure_threshold: Number of consecutive failed checks across all targets to declare an internet outage.
• request_timeout_seconds: Timeout in seconds for each HTTP request.
• retry_delay_seconds: Delay in seconds between retry attempts.
• ping_target: A list of URLs to be monitored.

Note

The configuration is validated on startup. The application exits with an error if check_interval_seconds, failure_threshold, request_timeout_seconds or retry_delay_seconds is 0, or if any ping_target URL does not use the http or https scheme.

Note

The config path is currently fixed to config.toml, resolved relative to the process's working directory -- there's no --config flag or env var to point it elsewhere. When running via Docker, the working directory is /app, so the file the binary actually reads is /app/config.toml.

Main Components and Workflow

• Loads configuration from config.toml.
• Initializes logging to file and console.
• Creates an asynchronous Tokio runtime for concurrent operations.
• Runs a monitoring loop that:
  • Checks the target URLs one by one (with retries) until the first success; if all of them fail, the round counts as a failure.
  • Logs success or failure for each attempt.
  • Tracks consecutive failures and logs internet outages when thresholds are met.
• Supports graceful shutdown on Ctrl+C (SIGINT).

Usage

Running Locally

1. Build the project:

   cargo build --release

2. Run the monitor:

   cargo run --release

   Or run the compiled binary directly:

   ./target/release/link_monitor

Running with Docker or Podman

Build the container image:

docker build -t link_monitor .
# or
podman build -t link_monitor .

Run the container, mounting your config and log directory:

docker run --rm \
  --user "$(id -u):$(id -g)" \
  -v "$(pwd)/config.toml":/app/config.toml:ro \
  -v "$(pwd)/logs":/app/logs \
  link_monitor

# Podman -- add the :Z suffix on SELinux systems (Fedora, RHEL, CentOS)
podman run --rm \
  --user "$(id -u):$(id -g)" \
  -v "$(pwd)/config.toml":/app/config.toml:ro,Z \
  -v "$(pwd)/logs":/app/logs:Z \
  link_monitor

Note

The image ships with a default config.toml baked in, so docker run link_monitor (with no mounts at all) works out of the box. Mounting your own file at /app/config.toml overrides it -- no rebuild needed to change settings.

Both mounts target /app/..., not /etc/link_monitor/...: the binary resolves config.toml and its log_file setting relative to its working directory, which is /app inside the container.

The container runs as a dedicated non-root user. --user "$(id -u):$(id -g)" makes it run as you instead, so it can write to your bind-mounted logs/ directory (owned by your host user) without a permission error. Not required on Docker Desktop (macOS/Windows), which handles this automatically.

Stopping the Application

Press Ctrl+C to stop the application gracefully. It will log shutdown events.

Viewing Logs

• View container logs in real-time:

  docker logs -f <container_id_or_name>
  podman logs -f <container_id_or_name>

• View log files on the host machine (assuming the logs/ directory is mounted):

  tail -f logs/internet_monitor.log

License

This project is licensed under the terms of the GNU General Public License v3.0 license. See the LICENSE file for details.