changedetection.io is a self-hosted web application for monitoring web pages for content changes. It periodically fetches URLs, computes diffs (text, JSON, image, or stock/price), and sends notifications via 100+ channels (Apprise). The system is built on Flask with Socket.IO for real-time UI updates, a pluggable processor architecture (text_json_diff, restock_diff, image_ssim_diff), and an LLM integration layer (via litellm) for intelligent change summarization and intent-based filtering. It supports multiple fetcher backends (requests, Playwright, Selenium, Puppeteer), browser automation steps, RSS feeds, and a REST API with OpenAPI spec. Architecturally, it is a monolith with background workers: a priority queue (RecheckPriorityQueue) dispatches watch rechecks to async workers, which fetch content, run processors, and trigger notifications. The datastore is file-based JSON with atomic writes and schema migrations. The frontend uses jQuery, SCSS, and custom JavaScript for diff visualization, visual selectors, and real-time queue monitoring. The plugin system (pluggy) allows extending fetchers, processors, conditions, and UI elements. Key entry points include the CLI (changedetection.py), the Flask app factory (flask_app.py), the worker pool (worker_pool.py), and the notification service (notification_service.py). External dependencies include Playwright, Apprise, litellm, lxml, and various image processing libraries (OpenCV, libvips). The codebase is well-tested with over 120 test files covering security, integration, and unit tests.
Ciao is a self-contained, zero-external-dependency HTTP(S) endpoint monitoring application built with Ruby on Rails 8. It schedules periodic health checks with cron syntax using the in-process rufus-scheduler, stores state in a local SQLite database, and notifies users of status changes via email or configurable webhooks (e.g., Slack, Rocket.Chat). The application also monitors TLS certificate expiration for HTTPS endpoints and sends alerts when certificates are due to expire. It provides a web UI with a dashboard, a RESTful JSON API, optional Prometheus metrics, and HTTP Basic authentication. The codebase is a standard Rails monolith with a single process for web server, scheduler, and background work, making it easy to deploy (Docker, Helm chart, or direct Ruby). The architecture is simple but effective for small-to-medium monitoring needs.