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GURL - Go URL Email Crawler

An intelligent web crawler built in Go that extracts email addresses from websites with precision and speed.

🚀 Fast, intelligent, and scalable email discovery for modern web applications

✨ Features

• 🧠 Intelligent Crawling: Prioritizes contact and information pages
• 🌍 Multi-language Support: Recognizes keywords in 6 languages (Spanish, English, French, German, Italian, Portuguese)
• 🔄 Meta Redirects: Automatically follows HTML meta redirects
• ⚡ Redis Cache: Smart caching with 12-month persistence and 5,400x speed improvement
• 🚀 Async Processing: Background jobs with webhook notifications
• 🔍 Auto Deduplication: Automatically removes duplicate emails
• 🐳 Dockerized: Easy deployment with Docker Compose
• 📡 REST API: Both synchronous and asynchronous endpoints
• ⚙️ Configurable Depth: Explore up to 3 levels deep (configurable)

☕ Support

If you like this project, consider buying me a coffee ☕💛

📋 Requirements

• Docker
• Docker Compose

🚀 Quick Start

Option 1: Use Pre-built Docker Image (Recommended)

# Pull and run the latest image
docker run -d --name gurl-crawler \
  -p 8080:8080 \
  -p 6379:6379 \
  luisra51/gurl:latest

# Or use with external Redis
docker run -d --name gurl-crawler \
  -p 8080:8080 \
  -e REDIS_HOST=your-redis-host \
  -e REDIS_PORT=6379 \
  luisra51/gurl:latest

Option 2: Clone and Build from Source

git clone https://github.com/luisra51/gurl.git
cd gurl
docker-compose up --build

2. Use the API

Service will be available at http://localhost:8080

Synchronous Scanning (Immediate Response)

# Basic scan
curl "http://localhost:8080/scan?url=example.com"

# With specific protocol
curl "http://localhost:8080/scan?url=https://company.com"

Response:

{
  "emails": ["[email protected]", "[email protected]"],
  "from_cache": false,
  "crawl_time": "2.3s"
}

Asynchronous Scanning (For Slow URLs)

curl -X POST "http://localhost:8080/scan/async" \
  -H "Content-Type: application/json" \
  -d '{
    "url": "slow-website.com",
    "webhook_url": "https://your-api.com/webhook",
    "callback_id": "optional-tracking-id"
  }'

Immediate Response:

{
  "job_id": "uuid-123-456-789",
  "status": "queued",
  "estimated_time": "30-60s",
  "webhook_url": "https://your-api.com/webhook",
  "check_status_url": "/scan/status/uuid-123-456-789"
}

Webhook Callback (When Complete):

{
  "job_id": "uuid-123-456-789",
  "callback_id": "optional-tracking-id",
  "status": "completed",
  "url": "https://slow-website.com",
  "emails": ["[email protected]"],
  "crawl_time": "45.2s",
  "pages_visited": 15,
  "completed_at": "2025-08-07T10:30:00Z"
}

3. Response Types

Success with Emails Found:

{
  "emails": ["[email protected]", "[email protected]"],
  "from_cache": true,
  "crawl_time": "396µs"
}

Success without Emails:

{
  "emails": [],
  "from_cache": false,
  "crawl_time": "2.1s"
}

Error:

{
  "error": "Invalid URL provided"
}

🌍 Multi-language Support

The crawler intelligently recognizes contact-related keywords in 6 languages:

• 🇪🇸 Spanish: contacto, información, equipo, nosotros, empresa
• 🇺🇸 English: contact, about, team, support, help, office
• 🇫🇷 French: nous-contacter, équipe, aide, assistance, bureau
• 🇩🇪 German: kontakt, über-uns, impressum, unser-team, hilfe
• 🇮🇹 Italian: contatti, chi-siamo, squadra, informazioni, supporto
• 🇵🇹 Portuguese: contato, sobre-nos, equipe, ajuda, suporte

43+ keywords total across all languages for maximum coverage

🔌 API Endpoints

Synchronous Endpoints

Method	Endpoint	Description
GET	/scan?url=<website>	Scan website (immediate response)
GET	/cache/stats	View Redis cache statistics
DELETE	/cache/invalidate	Clear all cache
DELETE	/cache/invalidate?url=<website>	Clear specific URL cache

Asynchronous Endpoints

Method	Endpoint	Description
POST	/scan/async	Create async scan job
GET	/scan/status/<job_id>	Check job status
DELETE	/scan/cancel/<job_id>	Cancel queued job
GET	/scan/jobs	View active job statistics

Advanced Usage Examples

# View cache statistics
curl "http://localhost:8080/cache/stats"

# Check async job status
curl "http://localhost:8080/scan/status/uuid-123-456"

# Cancel queued job
curl -X DELETE "http://localhost:8080/scan/cancel/uuid-123-456"

# View active jobs and statistics
curl "http://localhost:8080/scan/jobs"

# Clear complete cache
curl -X DELETE "http://localhost:8080/cache/invalidate"

⚙️ Configuration

Environment Variables

# Crawler Settings
CRAWLER_MAX_DEPTH=3                    # Maximum crawling depth
CRAWLER_DEDUPLICATE_EMAILS=true       # Remove duplicate emails

# Cache Settings  
CACHE_ENABLED=true                     # Enable Redis cache
CACHE_EXPIRATION_MONTHS=12             # Cache TTL in months

# Async Processing Settings
ASYNC_ENABLED=true                     # Enable async processing
ASYNC_WORKERS=3                        # Number of parallel workers
ASYNC_JOB_TIMEOUT_SECONDS=300          # Job timeout (5 minutes)
ASYNC_WEBHOOK_RETRIES=3                # Webhook retry attempts

# Redis Configuration
REDIS_HOST=localhost                   # Redis host
REDIS_PORT=6379                        # Redis port
REDIS_PERSIST_DISK=false              # Disk persistence (prod: true)

# Server Configuration
SERVER_PORT=8080                       # Server port
SERVER_HOST=0.0.0.0                   # Server host

How It Works

• 🎯 Smart Crawling: Prioritizes contact pages with multilingual keywords
• 📊 Depth Control: Configurable depth (default: 3 levels)
• ⚡ Cache System: Redis-based caching with 12-month TTL
• 🔄 Auto Deduplication: Automatic email normalization and deduplication
• 🚀 Performance: 5,400x faster responses with cache hits

🏗️ Project Architecture

/
├── .env                     # Environment variables (development)
├── .env.example             # Configuration example
├── go.mod                   # Go dependencies
├── Dockerfile               # Container definition
├── docker-compose.yml       # Redis + App services
├── scan_urls.sh             # Batch processing script
├── cmd/
│   └── crawler/
│       └── main.go          # Application entry point
└── internal/
    ├── cache/
    │   └── cache.go         # Redis cache management
    ├── config/
    │   └── config.go        # Environment configuration
    ├── crawler/
    │   └── crawler.go       # Core crawling logic
    ├── handler/
    │   └── handler.go       # HTTP endpoints (sync + async)
    └── jobs/
        ├── types.go         # Job data types
        ├── queue.go         # Redis job queue
        └── worker.go        # Worker system + webhooks

Core Components

• 🗄️ Cache Layer: Redis with configurable TTL and optional persistence
• ⚙️ Job Queue: Redis-based async system with parallel workers
• 📡 Webhook System: Result delivery with retries and exponential backoff
• 🌐 Multi-language: 43+ keywords across 6 languages
• 🔧 Config Management: Environment-based configuration

🔧 Development

With Docker (Recommended)

# Copy environment variables
cp .env.example .env

# Start complete stack
docker-compose up --build

Without Docker

# Install Redis locally
# Ubuntu/Debian: sudo apt install redis-server
# macOS: brew install redis

# Start Redis
redis-server

# Install Go dependencies
go mod tidy

# Run application
go run cmd/crawler/main.go

🤝 Contributing

We welcome contributions! Here's how you can help:

Ways to Contribute

• 🐛 Bug Reports: Found a bug? Open an issue
• ✨ Feature Requests: Have an idea? Start a discussion
• 📝 Documentation: Improve docs, add examples, fix typos
• 🌍 Translations: Add support for more languages
• 🧪 Testing: Write tests, test edge cases
• 💻 Code: Implement new features or fix bugs

Development Setup

1. Fork the repository
2. Clone your fork:

   git clone https://github.com/your-username/gurl.git
   cd gurl

3. Create a feature branch:

   git checkout -b feature/amazing-feature

4. Make your changes
5. Test your changes:

   docker-compose up --build
   # Test your changes

6. Commit and push:

   git commit -m "Add amazing feature"
   git push origin feature/amazing-feature

7. Open a Pull Request

Code Style

• Follow standard Go conventions (go fmt, go vet)
• Add tests for new features
• Update documentation for API changes
• Use meaningful commit messages

📝 Limitations

• JavaScript: Does not execute JavaScript, only analyzes static HTML
• Single Page Applications: Limited on SPAs that load content dynamically
• Rate limiting: Does not implement throttling between requests
• Same domain: Only crawls pages from the same base domain

🚀 Use Cases

• 💼 Lead Generation: Find contact emails from company websites
• 🔍 Research Automation: Collect contact information at scale
• 📊 Competitive Analysis: Study competitor contact pages
• 🔗 API Integration: Integrate with CRMs via webhooks
• 📦 Batch Processing: Process thousands of URLs with scan_urls.sh
• 🏗️ Microservices: Email discovery service for distributed architectures

🐳 Docker

Using Docker Hub Image (Production)

# Single container (no Redis persistence)
docker run -d --name gurl-crawler \
  -p 8080:8080 \
  luisra51/gurl:latest

# With Docker Compose (includes Redis)
docker-compose -f docker-compose.hub.yml up -d

# Production with external Redis
docker run -d --name gurl-crawler \
  -p 8080:8080 \
  -e REDIS_HOST=your-redis-host \
  -e REDIS_PORT=6379 \
  -e REDIS_PERSIST_DISK=true \
  -e ASYNC_WORKERS=5 \
  -e CACHE_EXPIRATION_MONTHS=12 \
  luisra51/gurl:latest

Development (from source)

# Quick development (no persistence)
docker-compose up --build

# Fast rebuilds
docker-compose up --build crawler-app

# Clean and start fresh
docker-compose down -v && docker-compose up --build

Manual build

docker build -t email-crawler .
docker run -p 8080:8080 email-crawler

🔍 Monitoring and Debugging

# View cache statistics
curl "http://localhost:8080/cache/stats"

# View worker and job status
curl "http://localhost:8080/scan/jobs"

# Application logs
docker-compose logs -f crawler-app

# Redis logs
docker-compose logs -f redis

# Enter container for debugging
docker-compose exec crawler-app sh