Websocket Compression

Pounce supports permessage-deflate compression for WebSocket connections, reducing bandwidth usage by 60-80% for text messages with repetitive content (JSON, HTML, etc.).

Configuration

WebSocket compression is enabled by default:

from pounce import ServerConfig

config = ServerConfig(
    websocket_compression=True,  # Default: True
    websocket_max_message_size=10_485_760,  # 10 MB (default)
)

How It Works

1. Negotiation: When a client requestsSec-WebSocket-Extensions: permessage-deflate, pounce automatically negotiates and responds with the same header in the 101 response.

2. Transparent: Compression and decompression are handled automatically bywsproto. Your ASGI app sends/receives uncompressed data—pounce handles the compression at the protocol layer.

3. Per-Message: Each WebSocket message is compressed independently, allowing for efficient streaming and minimal memory overhead.

Benefits

• Bandwidth Savings: 60-80% reduction for text data (JSON, HTML, XML)
• Lower Latency: Smaller payloads = faster transmission over slow networks
• Mobile-Friendly: Reduces data usage for mobile clients
• Zero App Changes: Works transparently with existing ASGI WebSocket apps

Example

# Your ASGI app doesn't change—compression is automatic
async def websocket_app(scope, receive, send):
    if scope["type"] == "websocket":
        await send({"type": "websocket.accept"})

        # Send a large JSON payload—automatically compressed
        data = {"users": [...]}  # Large JSON object
        await send({"type": "websocket.send", "text": json.dumps(data)})

        await send({"type": "websocket.close"})

Performance

Compression adds minimal CPU overhead (< 5% for typical workloads) while providing significant bandwidth savings:

Disabling Compression

To disable compression (e.g., for already-compressed data like images or encrypted content):

config = ServerConfig(websocket_compression=False)

Requirements

WebSocket compression requires thewsprotolibrary:

pip install pounce[ws]

Compatibility

Permessage-deflate is widely supported:

• All modern browsers (Chrome, Firefox, Safari, Edge)
• Node.jswslibrary
• Pythonwebsocketslibrary
• Gogorilla/websocket

Spec Compliance

Implements RFC 7692 (WebSocket Compression Extensions).