Snippet

Async Request Context Middleware for Correlation ID Injection

This middleware demonstrates asynchronous HTTP request handling in Django, capturing header context and ensuring exception propagation across async boundaries.

snippet.py

python

from typing import Callable, Awaitable
from django.http import HttpRequest, HttpResponse
 
class AsyncCorrelationMiddleware:
    def __init__(self, get_response: Callable[[HttpRequest], Awaitable[HttpResponse]]):
        self.get_response = get_response
 
    async def __call__(self, request: HttpRequest) -> HttpResponse:
        request.correlation_id = request.headers.get("X-Correlation-ID", "anon")
        try:
            response = await self.get_response(request)
            response["X-Correlation-ID"] = request.correlation_id
            return response
        except Exception as exc:
            request.meta_error = str(exc)
            raise

django

Breakdown

class AsyncCorrelationMiddleware:

Defines an asynchronous middleware class compatible with Django's ASGI pipeline.

def __init__(self, get_response: Callable[[HttpRequest], Awaitable[HttpResponse]]):

Stores the downstream asynchronous response handler executable.

async def __call__(self, request: HttpRequest) -> HttpResponse:

Defines the async call interface invoked for processing incoming HTTP requests.

request.correlation_id = request.headers.get("X-Correlation-ID", "anon")

Extracts incoming correlation header or assigns a default value to the request.

response = await self.get_response(request)

Awaits downstream request processing asynchronously to generate the response.

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Async Request Context Middleware for Correlation ID Injection

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