new(cfg) -> cache

Create a new DNS cache instance

Configuration fields (all optional):

• max_entries — maximum positive cache entries (default 10000, in-memory only)

• max_negative — maximum negative cache entries (default 5000, in-memory only)

• min_ttl — minimum TTL floor in seconds (default 30)

• max_ttl — maximum TTL cap in seconds (default 86400)

• max_negative_ttl — maximum negative TTL cap in seconds (default 300)

• sweep_interval — seconds between expired-entry sweeps (default 120, in-memory only)

• mneme — enable MNEME backend (boolean, opens db at mneme_path)

• mneme_db — pre-opened MNEME db handle (for sharing with other consumers)

• mneme_path — MNEME database file path (default /var/cache/recall/dns.mneme)

The returned cache object provides these methods:

• cache:get(qname, qtype) — returns cached records with adjusted TTLs, or nil

• cache:put(qname, qtype, records, ttl) — store records with TTL clamping

• cache:get_negative(qname, qtype) — returns {rcode, soa} for NXDOMAIN/NODATA, or nil

• cache:put_negative(qname, qtype, rcode, soa_record) — store negative response

• cache:sweep() — remove expired entries (in-memory: rate-limited by sweep_interval; MNEME: purge_expired)

• cache:flush() — clear all entries

• cache:stats() — returns {backend, size, neg_size}