ASGI

ASGI#

ASGI (Asynchronous Server Gateway Interface) is the asynchronous counterpart to WSGI, designed for modern Python web applications that need to handle asynchronous operations. While WSGI was built around a synchronous request-response model, ASGI extends this to support asynchronous code patterns and other protocols like WebSockets, HTTP/2, and Server-Sent Events.

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Key aspects of ASGI#

  1. It supports asynchronous request handling, allowing servers to process multiple requests concurrently without blocking

  2. It’s protocol-agnostic, supporting not just HTTP but also WebSockets and other bidirectional communication protocols

  3. It enables long-lived connections necessary for real-time applications

  4. It maintains backward compatibility with WSGI applications

An ASGI application is a callable that: - Takes three parameters: scope (connection information), receive (async function to receive messages), and send (async function to send messages) - Is typically defined using Python’s async/await syntax

Popular ASGI frameworks and servers include: - FastAPI - Django Channels - Starlette - Quart - Uvicorn - Daphne - Hypercorn

ASGI is particularly valuable for applications that: - Need to handle many concurrent connections - Require real-time features like chat applications or live updates - Benefit from WebSocket support for bidirectional communication - Need to perform I/O operations like database queries without blocking the server

The transition from WSGI to ASGI represents the Python web ecosystem’s evolution to better support modern web development requirements, especially for real-time and high-performance applications.