Owns the :mailglass_inbound_rate_limit ETS table and the small amount of work that must be serialized: missing-key admission, bounded contention fallback, and idle sweeping. Mailglass.RateLimiter.AtomicBucket keeps the normal path as a fixed-point compare-and-swap loop; only exhausted callers enter this package-local owner mailbox.

ETS opts (OTP 27+) — copied verbatim from core

• :set — single-entry-per-key bucket
• :public — cross-process read/write without owner-forwarding
• :named_table — caller references :mailglass_inbound_rate_limit directly
• read_concurrency: true — hot read path optimization
• write_concurrency: :auto — OTP 27 flag for lock striping
• decentralized_counters: true — OTP 27 flag, per-scheduler counters

Crash semantics

If this process crashes, BEAM deletes the ETS table. The supervisor restarts TableOwner and ensure_table/0 recreates the canonical table before every owner ETS operation. Counter state is intentionally ephemeral across a restart, but callers re-admit through the replacement owner rather than crashing on :badarg.

Reserved-singleton note

This module uses name: __MODULE__. It is library-internal machinery (not a user-facing singleton) and is the documented reserved-singleton exception, mirroring Mailglass.RateLimiter.TableOwner. The inbound ETS table must be a process-stable named table so the limiter hot path can reach it without a registry lookup.