No shared ID across the log lines for one request

Same bug, two users, and no way to tell whose log lines are whose.

Intermediate to advancedRead 4 minDoing: about an hour, with your project open5 steps

What you'll have at the end

Every log line your FastAPI app writes while handling one request carries that request's own ID; two requests running at the same time never share it, and grepping one ID pulls back exactly that request's lines and nothing else's.

Before you start

You need

A FastAPI app whose route handlers already call Python's standard logging module somewhere, even though the output right now gives no way to tell one request's lines from another's.

Not covered

Sending this ID on to another service your API calls, or matching it against that service's own logs: that needs its own cross-service tracing setup.

Leans on

5 steps

Where to go next

Push live updates to a browser with a WebSocket instead of polling

reach for that one instead when the connection itself is long-lived, since there's no single request to stamp there, only one connection to keep track of over time.

Checked 18 Aug 2026

Part of the FastAPI cookbook