Upgrading one of the oldest components in Cloudflare’s software stack

What this post added

Modified NGINX's upgrade mechanism to control individual workers instead of the entire master process and its workers simultaneously. This involves disabling automatic worker restarts, shutting down one old worker, starting one new worker, and then re-enabling automatic restarts. This process is repeated for all workers, ensuring a stable memory footprint and preventing CPU core contention by carefully managing worker replacement and CPU pinning.