When multiple queries for the same (domain, qtype) arrive concurrently and all miss the cache, only the first triggers recursive resolution. Subsequent queries wait on a broadcast channel for the result. Prevents thundering herd where N concurrent cache misses each independently walk the full NS chain, compounding timeouts. Uses InflightGuard (Drop impl) to guarantee map cleanup on panic/cancellation — prevents permanent SERVFAIL poisoning. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
1.4 KiB
1.4 KiB