On 2026-10-09 (sdbees) both :8000 API workers had 7 of 8 gthread pool
threads blocked in tcp_recvmsg -> sk_wait_data; /health and
/api/blocked-ips hung 40s+ while the container reported healthy.
The app makes no in-process outbound socket reads (every ACME/HAProxy
interaction is an already-bounded subprocess). The blocked reads were
gunicorn gthread reading the CLIENT socket: TConn.init() calls
setblocking(True), i.e. timeout None, before parsing the request. Any
peer that sends a few bytes and goes quiet (a TLS ClientHello on this
plain-HTTP port, scanners; :8000 is published on 0.0.0.0) pins a pool
thread forever. gunicorn --timeout does not catch it (gthread only
watches the main thread's heartbeat), --max-requests never triggers on
a worker that finishes nothing, and socket.setdefaulttimeout() is reset
by setblocking(True).
- haproxy_gunicorn_worker.TimeoutThreadWorker (used for :8000 and :8080):
* per-connection socket timeout HAPROXY_MGR_CLIENT_TIMEOUT (20s),
re-applied on keep-alive reuse; bounds socket I/O, not handling time
* watchdog: if every pool thread has been in the same request for more
than HAPROXY_MGR_WEDGE_SECONDS (1200s, > certbot renew's 900s), dump
all thread stacks and exit so the master respawns the worker
* client timeouts logged as one INFO line, not a traceback
- haproxy_manager: socket.setdefaulttimeout (HAPROXY_MGR_SOCKET_DEFAULT_TIMEOUT,
60s) as defence in depth for any future in-process client; /health now
reports the answering worker's busy/total threads and oldest request age
- scripts/healthcheck.sh: probes :8000/health (4s) AND :80; image
HEALTHCHECK uses it (WHP's --health-cmd override must too)
- scripts/test-gunicorn-socket-timeouts.py (12 tests, real gunicorn),
added to the Docker build gate
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
