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2026-10-08-bbr-deploy-setup

title: Run deploy setup before the first deploy with BBR affects: dartway_cli: "0.24.0"​

Who is affected​

Every existing server before its first deploy run with a CLI that carries the BBR guard (#470, dartway_cli 0.24.0). The server may have tcp_bbr on disk without having loaded it, so BBR is absent from tcp_allowed_congestion_control.

What to change​

Run setup once on each server, before its next deploy run:

dart run dartway_cli:dartway deploy setup --env <environment>

Setup is idempotent. If it has not run, the deploy run guard stops before replacing anything and prints:

BBR congestion control is not allowed on the server. Run `dart run dartway_cli:dartway deploy setup` once on this server, then deploy again.

With --progress json, the message goes to stderr and the run_finished event carries reason: "bbr-unavailable".

How to check​

After the next deploy run, run dart run dartway_cli:dartway deploy check --env <environment>. Confirm that proxy-congestion-control (The front proxy uses BBR congestion control) passes, and so does host-congestion-control. In the app directory on the server, you can also read the value checked in the running proxy directly:

docker compose exec -T nginx cat /proc/sys/net/ipv4/tcp_congestion_control

It prints bbr.