We ran into the annoying Envoy 503 bug in our prod and needed some quick tools to help figure out what was going on with TCP connections and HTTP requests.

https://github.com/vishnugt/TCPFinMonitor. Live - https://keepalive.gt.ms/

This tool tracks TCP FIN packet timing to see how upstream connections are closing and how keep-alives behave. It helped me spot when connections were closing too early or timing out, which was causing those 503 errors.

https://github.com/vishnugt/hyperbin

A fast, minimal httpbin clone written in Rust. It’s way faster(20x throughput) than the usual httpbin and useful for testing HTTP clients and debugging requests without extra noise.

These aren’t polished, just some stuff I needed to iron out the issue.