nx_sig2_txq.nx

nx_sig2_txq.nx -- FRAME-ATOMIC non-blocking WebSocket send queue for the signaling relay. (four-pillar ADDRESS at the transport layer; root cause: the relay's blocking fan-out writes.) THE TWO DEFECTS THIS CLOSES (source-confirmed 2026-07-09, [[project-nishi-videoops-four-pillars]]): 1. BLOCKING WRITES in a single-threaded fan-out: one slow receiver's full socket buffer STALLED every room on the relay (head-of-line). Writes here use sendto(MSG_DONTWAIT) -- the relay NEVER sleeps on a receiver. (Write-side only: the read path keeps its blocking semantics.) 2. PARTIAL-FRAME POISON: _wss_write_n bailed mid-frame on w<=0, leaving a torn WebSocket frame on the stream -- every later byte misparsed (the field's silent video garbage). Here a frame either goes out WHOLE (possibly across POLLOUT continuations from the queue) or is dropped WHOLE before any byte touches the wire. Torn-frame-unavoidable (partial direct write + queue full) is FATAL by design: the caller must treat the conn as poisoned and let the reap path close it -- fail-stop beats fail-dirty. Per-conn state (caller-allocated, indexed by conn slot ci): txq slab: NX_S2TX_QBYTES per conn -- queued raw wire bytes (whole frames / frame remainders) txh[ci]: queue head offset txl[ci]: queued byte count Drop policy: a frame that cannot fit WHOLE in the queue is dropped whole and counted by the caller (video P-gap -> the client's seq check + kreq recovers in ~1 RTT; JSON control re-sends). license_tier: ORIGINAL