Source code for lalandre_core.http.middleware

"""Reusable HTTP instrumentation middleware factory for FastAPI services."""

import time
import uuid
from typing import Any, Callable

import structlog
from fastapi import Request, Response
from starlette.middleware.base import RequestResponseEndpoint




def make_http_instrumentation_middleware(
    observe_fn: Callable[..., None],
) -> Callable[[Request, RequestResponseEndpoint], Any]:
    """Build a middleware that records per-request latency and status metrics."""

    async def instrument_http_requests(
        request: Request,
        call_next: RequestResponseEndpoint,
    ) -> Response:
        request_id = request.headers.get("x-request-id") or uuid.uuid4().hex[:12]
        structlog.contextvars.clear_contextvars()
        structlog.contextvars.bind_contextvars(request_id=request_id)

        started_at = time.perf_counter()
        status_code: int = 500
        try:
            response: Response = await call_next(request)
            status_code = response.status_code
            response.headers["x-request-id"] = request_id
            return response
        finally:
            observe_fn(
                path=request.url.path,
                method=request.method,
                status_code=status_code,
                duration_seconds=time.perf_counter() - started_at,
            )

    return instrument_http_requests