Deltamon

Web page change detection and monitoring with a visual CSS selector.

Features

• Visual Selector — Click elements on pages to automatically generate CSS selectors
• Change Detection — Monitor pages for content changes with diff generation
• Regex Filtering — Filter content with whitelist/blacklist regex patterns
• Webhooks — Send notifications when changes are detected
• Scheduling — Configurable check intervals per monitor
• Bulk Operations — Manage multiple monitors at once

Quick Start

# Run with Docker
docker run -p 3000:3000 \
  -e DATABASE_URL=postgres://user:pass@host:5432/deltamon \
  harbor.wuastbude.de/webmon/deltamon:latest

Or with docker-compose:

services:
  deltamon:
    image: harbor.wuastbude.de/webmon/deltamon:latest
    ports:
      - 3000:3000
    environment:
      - DATABASE_URL=postgres://user:pass@host:5432/deltamon
    restart: unless-stopped

Configuration

Environment variables:

Variable	Required	Description
DATABASE_URL	Yes	PostgreSQL connection string
DATABASE_SCHEMA_STRATEGY	No	Schema startup mode: auto (default), migrate, push, or none
PUPPETEER_WS_ENDPOINT	No	External browser endpoint (e.g., browserless.io)

Tech Stack

• Next.js 16 — React framework with App Router
• Drizzle ORM — TypeScript ORM for PostgreSQL
• Graphile Worker — Background job processing
• Puppeteer — Headless Chrome for page fetching
• Tailwind CSS + DaisyUI — Styling

Development

# Install dependencies
just setup

# Start development server
just dev

# Run project checks
just check  # lint + typecheck
just test   # Docker/package/build checks

# Apply database migrations
bun run db:migrate

Building

# Build Next.js
bun run build

# Build worker
bun run build:worker

# Build Docker image
just docker-build

Notification Targets

Deltamon supports two notification target types:

• HTTP JSON: sends the full webhook payload with POST to the configured URL and custom headers.
• Matrix Room: sends only the Matrix m.room.message content with PUT to the configured homeserver, room ID, and access token.

Matrix room messages use msgtype: "m.notice" and include the same readable Added/Removed sections as the HTTP JSON payload's message object.

HTTP JSON Payloads

Web Monitor

When content changes are detected on a web page:

{
  "monitor": {
    "id": "abc123",
    "name": "My Monitor",
    "url": "https://example.com",
    "human_url": "https://example.com/page",
    "type": "web"
  },
  "check": {
    "id": "pending",
    "checked_at": "2024-01-15T10:30:00Z"
  },
  "changes": {
    "added": "New content that was added",
    "removed": "Content that was removed",
    "diff": "- Old line\n+ New line"
  },
  "message": {
    "msgtype": "m.notice",
    "body": "**My Monitor(https://example.com/page)**\n\n**Added:**\nNew content that was added\n\n**Removed:**\nContent that was removed",
    "format": "org.matrix.custom.html",
    "formatted_body": "<strong>My Monitor(<a href=\"https://example.com/page\">https://example.com/page</a>)</strong><br><br><strong>Added:</strong><br><pre><code>New content that was added</code></pre><br><strong>Removed:</strong><br><pre><code>Content that was removed</code></pre>"
  },
  "content": {
    "full": "The complete extracted content after applying regex patterns"
  },
  "metadata": {
    "timestamp": "2024-01-15T10:30:00Z",
    "app": "Deltamon"
  }
}

RSS Monitor

When new articles are detected in an RSS/Atom feed:

{
  "monitor": {
    "id": "abc123",
    "name": "My RSS Feed",
    "url": "https://example.com/feed.xml",
    "human_url": "https://example.com",
    "type": "rss"
  },
  "feed": {
    "title": "Example Blog",
    "url": "https://example.com/feed.xml"
  },
  "new_items": [
    {
      "id": "https://example.com/post/123",
      "title": "New Blog Post Title",
      "description": "Short summary of the post",
      "content": "Full HTML content of the article (if available)",
      "url": "https://example.com/post/123",
      "published": "2024-01-15T09:00:00Z",
      "authors": ["John Doe", "Jane Smith"]
    }
  ],
  "metadata": {
    "timestamp": "2024-01-15T10:30:00Z",
    "app": "Deltamon",
    "new_items_count": 1
  }
}

License

MIT