A connection that arrives while the listeners are paused is answered 503 instead of waiting in the backlog #359

http_server_pause_listeners (src/http_server_class.c) calls stop() on each listen event and expects new connections to wait in the kernel backlog until the resume. php-async cannot stop a uv_listen (true-async/php-async#305), so accepts go on: each connection that arrives during a pause reaches http_server_accept_callback, and the hard-cap safety net answers it 503, a path its own comment calls rare.

Reproduction: tests/phpt/server/h1/062-h1-paused-listener-leaves-the-backlog.phpt, setMaxConnections(2), two parked requests, a third client during the pause: 503 Service Unavailable on 5 of 5 runs, while getTelemetry()['listeners_paused'] reads true.

The comments at the backpressure primitives are wrong on a second point: under SO_REUSEPORT the kernel keeps hashing new connections to a paused worker's socket, so they wait for that worker (or are dropped once its backlog is full) rather than going to another one.

The fix is in php-async. This repository gets the tests (062, a burst past the cap, a re-pause during delivery), corrected comments, and two counters: accepts_refused_at_cap_total (nonzero means a pause did not hold) and accept_errors_total (accept failures were dropped without a trace).