const MIN_FREE: f64 = 0.10;Expand description
Free space below which retention stops waiting for the TTL.
This is not a setting and there is deliberately no key for it. Retention as a
TTL alone assumes the ingest rate the window was sized for; the first spike,
chatty service or debug level left on fills the volume before the clock
expires anything, every publish then fails ENOSPC, every export is NACKed,
and nothing in the process ever undoes it — the only thing that deletes
blocks is a clock that has not advanced far enough. The number the engine
needs is not “how full may I get”, it is read off the volume every sweep; the
only constant here is the margin, and 10% is enough headroom for the blocks
in flight (three signals’ target_block_bytes plus their staging copies) on
any volume big enough to hold a day of telemetry, while still leaving the
sweep room to act before publish starts failing.