Function build_cgroup_sampler_start_snippet 

pub fn build_cgroup_sampler_start_snippet(container_name: &str) -> String

Shell fragment starting the background sampler. It writes each sample to a temp file with mv, so the watcher never reads a half-written line, and ends by itself once the container is gone.

Where the cgroup is readable locally it reads it directly. Otherwise, with a private cgroup namespace (a mounted docker.sock), one long-lived docker exec -i answers one host tick per interval (issue #242); a successful read proves the container runs, so Docker is asked for liveness only after a failed round or when the stream ends. Without a usable stream it falls back to one docker exec per round; without sh in the image (exit 126/127) or without any readable cgroup (exit 3 from either exec, issue #247) it records the reason and stops. Other failed rounds are retried, each one doubling the wait up to CGROUP_SAMPLE_BACKOFF_MAX_SECONDS; a sample restores the interval. START_COMMAND_CGROUP_SAMPLE_INTERVAL_SECONDS=off disables sampling.