Shedding old code with ecdysis: graceful restarts for Rust services at Cloudflare

Cloudflare open-sourced ecdysis, a Rust library enabling zero-downtime service upgrades through graceful process restarts. After five years in production handling billions of requests across 330+ data centers, the library uses a fork-and-inherit model where child processes inherit listening sockets from parents, eliminating connection drops during restarts. It includes Tokio integration, systemd support, and explicit security controls. The library solves the critical problem of upgrading network services at scale without refusing connections or dropping established sessions.