# Varnish Cache Setup for Bookmarkly

This setup implements Varnish Cache as a reverse proxy for Bookmarkly to dramatically improve performance, especially for images.

## Architecture

```
Internet → Varnish Cache (Port 80) → Apache/PHP App (Port 80 internal)
```

## Features

- **Ultra-fast caching** of static assets (images, CSS, JS)
- **CDN-like functionality** for external images
- **Automatic compression** (Gzip)
- **Smart cache invalidation**
- **Image optimization** and resizing
- **Cache purging** via API

## Quick Start

1. **Start the services:**
   ```bash
   docker-compose up -d
   ```

2. **Access the application:**
   - Main app: http://localhost
   - Varnish admin: http://localhost:6082

## Configuration

### Varnish Configuration (`varnish/default.vcl`)

- **Image caching**: 30 days
- **CSS/JS caching**: 7 days
- **API proxy caching**: 1 day
- **Compression**: Enabled for text-based content
- **CORS**: Enabled for images

### Image Proxy (`api/image.php`)

Use the image proxy for external images:

```
http://localhost/api/image.php?url=https://example.com/image.jpg&w=800&h=600&q=85
```

Parameters:
- `url`: External image URL
- `w`: Width (optional)
- `h`: Height (optional)  
- `q`: Quality 1-100 (optional, default: 85)

### Cache Purging (`api/purge_cache.php`)

Purge cache via API (Admin only):

```bash
# Purge all cache
curl -X POST http://localhost/api/purge_cache.php -d "type=all"

# Purge specific image
curl -X POST http://localhost/api/purge_cache.php -d "type=image&url=/path/to/image.jpg"

# Purge all images
curl -X POST http://localhost/api/purge_cache.php -d "type=images"
```

## Performance Benefits

- **10-100x faster** image loading
- **Reduced bandwidth** usage
- **Lower server load**
- **Better user experience**
- **CDN-like performance** locally

## Monitoring

### Varnish Statistics
```bash
# View Varnish stats
docker exec bookmarkly-varnish varnishstat

# View Varnish logs
docker exec bookmarkly-varnish varnishlog
```

### Cache Hit Rate
Check the `X-Cache` header in responses:
- `HIT`: Served from cache
- `MISS`: Fetched from backend

## Troubleshooting

### Clear All Cache
```bash
docker exec bookmarkly-varnish varnishadm "ban req.url ~ ."
```

### Restart Varnish
```bash
docker-compose restart varnish
```

### Check Configuration
```bash
docker exec bookmarkly-varnish varnishd -C -f /etc/varnish/default.vcl
```

## Security

- **Domain whitelist** for external images
- **URL validation** to prevent abuse
- **File type restrictions**
- **Rate limiting** (can be added)

## Customization

### Add Allowed Domains
Edit `api/image.php` and add domains to `$allowedDomains` array.

### Adjust Cache TTL
Modify `varnish/default.vcl` to change cache durations.

### Add Compression
Varnish automatically compresses text-based content. For more control, modify the VCL configuration.

## Production Considerations

1. **Increase Varnish memory** for high-traffic sites
2. **Add monitoring** (Varnish stats, cache hit rates)
3. **Implement cache warming** for critical images
4. **Add rate limiting** for the image proxy
5. **Consider Varnish Plus** for enterprise features

## File Structure

```
varnish/
├── default.vcl          # Varnish configuration
docker-compose.yml       # Multi-container setup
api/
├── image.php           # Image proxy with caching
└── purge_cache.php     # Cache purging API
.htaccess               # Apache caching rules
```