Workerman requires pcntl and posix on Linux; without them the relay
printed "Please install pcntl extension" and exited immediately,
Docker kept restarting it, and nginx's DNS lookups for
dmtools-puzzle-relay intermittently failed whenever it happened to be
down mid-restart - the "could not be resolved" errors were a symptom
of this crash loop, not a separate networking problem. Local dev never
hit this because Workerman's Windows code path doesn't need either
extension.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
