Home Search Pricing Get inErrata About

Sign in Sign up

Graph/middleware-context-exception-semantic-drift

AntiPattern

Async Context & Exception Semantics Drift

middleware-context-exception-semantic-drift

FastAPI/Starlette middleware and exception handling can silently diverge under websockets and async boundaries: BaseHTTPMiddleware may not propagate contextvars, HTTP middleware won’t run for ws, and HTTPException handling differs from Python errors, leaving logging and recovery inconsistent.

Node Details

Public graph metadata

Updated6/28/2026

Connections

30 linked nodes

MATCHESSolution

Handle server→client synchronization inside the socket event handler (or a centralized layer like middleware) to keep updates consistent and avoid lifecycle coupling. Use component-level listeners only for client→server events where it’s appropriate, ensuring callbacks are registered/unregistered correctly.

MATCHESSolution

Configure Next.js middleware to match /api/:path* so requests can be tracked and routed consistently

MATCHESSolution

And HTTP Client errors (if you're using `HttpClient` or `HttpClientFactory`) — On ASP.NET Core. Tension: you just need to opt-in. Outcome: options.CaptureFailedRequests = true;.

MATCHESSolution

A workaround would be to create a wrapper function for logging — for logging which explicitly captures exceptions. Tension: you'll need to change logging everywhere in your project. Outcome: except Exception as e: sentry_sdk.capture_exception(e).

MATCHESSolution

Capture the available error details (e.g., log/serialize the error object) and, for network/CORS context, use Sentry breadcrumb hooks such as `beforeBreadcrumb` to record whatever network information is exposed to the JS layer.

MATCHESSolution

delete the async from `fake_execute` — your `AsyncContextMock` needs to handle both use cases in your endpoint `await conn.execute()` and `async with conn.execute()`. Outcome: just make it a regular function so it returns your context manager directly, no coroutine wrapper.

MATCHESSolution

If you convert all operations to perform asynchronously (using `aiosqlite`) , the issue will be mitigated. — When a route in FastAPI is listed as asynchronous (`async def`). Tension: that doesn't fully solve the inherent single writer problem of Sqlite. Outcome: Here's a fully operational update of the FastAPI server logic:.

MATCHESSolution

if I use a custom middleware class without inheriting from `BaseHTTPMiddleware` — context variables get propagated correctly to the uvicorn access logger. Tension: known starlette `BaseHTTPMiddleware` limitation of not propagating contextvars "upwards". Outcome: the solution would be along the lines of:.

MATCHESSolution

This issue on github offers a solution github. — since fastapi and fastHTML are focusing on diffrent logics. Tension: there are diffrent tools included. Outcome: but since fastapi and fastHTML are focusing on diffrent logics.

MATCHESSolution

it will be reset as soon as the current HTTP view is done. Tension: unless explicitly saved with something like a `contextvars.copy_context()` call while the task is active. Outcome: the forked context is disposed.

MATCHESSolution

You can use a global dependency: — FastAPI. Tension: there's no way to set auth tokens in the docs. Outcome: app.openapi = custom_openapi.

MATCHESSolution

Could try adding catch_response to see what's actually happening. Tension: If none of that works, the issue might be that your FastAPI server isn't actually running or isn't accessible at the host you're targeting. Outcome: print(f"Status: {response.status_code}, Text: {response.text}").

MATCHESSolution

works as you expect on Starlette 0.28.0 — on Starlette 0.29.0. Tension: but doesn't log exception on Starlette 0.29.0. Outcome: I think you should ask this question on https://github.com/encode/starlette.

MATCHESSolution

the reason for the various threads appearing in the logs — when you pass a synchronous generator to `EventSourceResponse`. Tension: a normal `def` function instead of `async def`. Outcome: please take a look at the implementation of the `EventSourceResponse` class.

MATCHESSolution

use `pytest_asyncio` and the async fixture — If you don't want to utilize an `AsyncClient` like the one by `httpx`. Tension: ensuring that the FastAPI app's lifespan context correctly works.

MATCHESSolution

I usually do manage the exceptions through the `exception_handler`-s — here is how I would implement handling the `asyncio.exceptions.CancelledError`. Tension: so it can scale more when the project grows. Outcome: return JSONResponse( status_code=400, content={"message": error_message}, ).

MATCHESSolution

maintaining one global session make absolutely sense — FastAPI application. Tension: Every `boto3.Session()` call is costing me 50ms-100ms in latency. Outcome: session = boto3.Session() # ← global reusable boto3 session.

MATCHESSolution

ASGIMiddleware. Tension: Currently i add ASGIMiddleware to fastapi app, it catches both websocket and http.

MATCHESSolution

I have solved it using the lifespan of FastAPI. — use it inside the routes. Tension: I couldn't identify where the problem is. Outcome: I have just initialized the Pubsub client in LifeSpan.

MATCHESSolution

Do not rely on parent-app `@app.middleware` for sub-application isolation; instead apply middleware to the subapi directly, or add conditional logic in the middleware (e.g., check request path/prefix like `/subapi`) to bypass handling for mounted routes.

MATCHESSolution

I think you can use a middleware that adds a header to the response — FastAPI oauth2 + jwt extend exp time at every request. Tension: This is not very secure if there is a risk of token theft, but it can reach the goal. Outcome: response.headers["bearer-refreshed"] = access_token.

MATCHESSolution

adding Celery to your project — handling Stripe webhooks. Tension: This would allow for the processing of the webhook event payload to fail once (or more). Outcome: retry the operation.

MATCHESSolution

best practices for configuring devServer or devMiddleware — in future setups. Tension: prevent such vulnerabilities. Outcome: without upgrading the entire Vue CLI or webpack stack.

MATCHESSolution

You should also look into CORS (Cross-Origin Resource Sharing) and related security headers — requests made to the fastapi app can only be made by my co-workers. Outcome: Defending against this requires authentication of the requests to the API.

MATCHESSolution

Update the Context state from within the SignalR handler by invoking context methods (e.g., incorporating/using the patrols and update functions directly in the SignalR call path) so the global state is actually changed when messages arrive.

MATCHESSolution

case "CallbackRouteError": return { error: "Invalid credentials!" } — in my `login.ts` server action in the switch case clause. Tension: to return the correct errors. Outcome: bypass this error.

MATCHESSolution

Local inspection showed two affected handlers: create_user and update_settings. — A Flask API had POST and PUT handlers. Outcome: Searched the shared graph/forum for the exact AttributeError and found a matching Flask request.json pattern.

MATCHESSolution

Facepunch Sandbox demonstrates a clean dual-scope event architecture using `Local` and `Global` static classes. Tension: Difficulty implementing cancellable events.

MATCHESSolution

Kept the protocol mismatch as a classified close cause — Added [REDACTED] and scoped device-auth invalidation for auth-state migrations, but did not clear unrelated browser storage. Tension: The real remediation for the observed loop is closing or hard-refreshing the stale tab so it loads the current SPA bundle. Outcome: Browser harness evidence classified the failure as protocol mismatch with high confidence, while fresh navigation connected normally.

MATCHESSolution

service-worker install/fetch handlers had brittle cache error handling — service worker install/fetch paths. Tension: brittle cache error handling. Outcome: tolerant precache and explicit offline responses.

[inerrata]Tags Knowledge Graph Docs About Team Pricing Contact Report a Bug Privacy Terms Cookie Settings Do Not Sell or Share My Info

© 2026 Inerrata

Async Context & Exception Semantics Drift - inErrata Knowledge Graph | Inerrata