sentinel-monitor 0.1.2

A fast, minimal CLI tool to monitor website uptime and SSL certificate health.

Sentinel — Uptime & SSL Monitor

A fast, minimal CLI tool to monitor website uptime and SSL certificate health concurrently from your terminal.

      

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The Problem

Managing multiple projects means keeping track of domain health and SSL expiration dates manually — which is tedious and easy to miss. Sentinel gives you an instant, locally executable snapshot of your web services without the overhead of a heavy monitoring stack or an external SaaS dependency.

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Key Features

• Concurrent checks — all sites are probed simultaneously using async I/O, not one by one
• SSL health tracking — extracts certificate expiry directly via raw TCP sockets, no third-party APIs
• Responsive terminal UI — color-coded output that adapts to your terminal width
• Declarative config — define all your targets in a single YAML file
• Graceful error handling — DNS failures, timeouts, and connection drops are caught and reported per site without crashing

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Installation

pip install sentinel-monitor

Or with uv:

uv tool install sentinel-monitor

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Quick Start

Generate a starter config in your current directory:

sentinel init

Run the monitor:

sentinel

Point to a specific config file:

sentinel -c /path/to/targets.yaml

Check version:

sentinel --version

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Configuration

settings:
  timeout: 5
  alert_webhook: ""  # optional: Discord/Slack webhook URL

sites:
  - name: "Google"
    url: "https://google.com"
  - name: "My API"
    url: "https://api.example.com"

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How It Works

Sentinel is built around three components:

Configuration Manager — parses targets.yaml into typed dataclasses, validates structure, and raises actionable errors on bad input.

Concurrency Engine — an asyncio event loop dispatches all HTTP checks simultaneously via httpx. Sites are never checked sequentially.

Network Probes — two probe types run per site:

• Uptime probe: async HTTP HEAD request — minimal bandwidth, no body fetched
• SSL probe: raw TCP socket wrapped with ssl.SSLContext to extract and parse X.509 certificate metadata, runs in a background thread via asyncio.to_thread to avoid blocking the event loop

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Development Setup

git clone https://github.com/tomi3-11/sentinel-monitor.git
cd sentinel-monitor
uv venv && source .venv/bin/activate
uv sync
sentinel -c targets.yaml

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Docker

docker build -t monitor .
docker run -t monitor sentinel -c targets.yaml

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License

MIT