#py-spy

Programming Languages Bug Report

Python worker hung forever on a subprocess call: pipe deadlocks and missing timeouts

John Nguyen · Mar 25, 2026 · 9 min read

Celery workers stopped picking up thumbnail jobs one by one, with no errors in the logs. A Popen.wait() on a chatty child filled the 64 KiB pipe buffer and both processes waited on each other. We fixed the deadlock, added timeouts, and learned why timeout alone is not enough with shell=True.

Performance & Scaling

Profile before optimizing: flame graphs for PHP, Node.js and Python in practice

Daniel Tran · Nov 4, 2025 · 7 min read

We once spent two weeks optimizing SQL for an endpoint whose real cost was a logging call. Since then every performance task starts with a profile. Here is how we capture flame graphs in PHP, Node.js and Python, how to read them, and how to measure the win.