# Huge data loss when deploying refinery configuration without restarting

## What's going on

Deploying new refinery.toml/rules.toml without restarting the refinery systemd service causes almost total trace loss: traces making it to Honeycomb drop to near zero after config deploy. The service keeps running and live-reload picks up the new rules. Deployment script wrote configs with Ruby's File.write then called systemctl start (a noop when already running).

## The verified fix

The reporter tracked the data loss down to how the config files were written: Ruby's File.write modifies the file in place while refinery's live-reload reads it. Switching the deployment script to `cp` instead of File.write fixed it, and trace volume returned to normal in the graphs. If your live-reload config deploys are mysteriously breaking sampling, try switching the write to an atomic replacement and see whether the loss disappears.

Source: https://github.com/honeycombio/refinery/issues/384

## How to use this

Take the question above and check if it matches what you're seeing. If it does, work through the verified fix step by step. Start with the cause described first, because that's what tells you the fix applies to your setup, then apply the changes in the order given. Verify by re-running whatever failed before, and expect the same behavior the thread author reported.