Detecting event loop blocking in asyncio
If you’re writing async Python, you’ve probably blocked the event loop without knowing it. Your code runs. Your tests pass. But in production, p90 latencies spike and timeouts appear seemingly at random. The culprit? Synchronous code hiding inside your async def functions. Python’s asyncio is cooperative. When you await something, you’re yielding control back to the event loop so other tasks can run. But if you call synchronous code, even accidentally, the entire event loop freezes. Every other coroutine waits. Every concurrent request hangs. Every other user gets blocked. ...