The claim poll holds a connection open server-side. Under gthread that
pinned one of a worker's 8 OS threads, so 14 agents at hold=25 left a
worker with 8 of 9 threads parked in timed sleep and UI requests hashed
to that worker waiting 12-24s. Hold was cut to 5s as an interim fix.
gevent removes the constraint rather than working around it: a held
connection is a greenlet and the per-worker ceiling is worker-connections
(2000), not 8 threads, so an idle hold no longer costs a UI request
anything. Measured at 700 simulated agents plus UI, integration and kiosk
traffic: zero errors, UI median 7.5ms, peak RSS 479MB. CPU is the binding
resource, not memory or DB connections.
With that gone the 5s hold is a liability. Hold length sets the fleet's
request rate, not its concurrency, because the agent re-polls immediately
on a 204 - so hold=5 is 5x the requests of hold=25, against a burst
bottleneck that measured as TLS handshake CPU. 25 also restores the
margin against the agent's MinIdlePollDuration=5s floor used to tell a
normal hold-window close apart from a transient failure; at 5 it was
~20ms.
Timeout raised to 60 so gunicorn cannot kill a healthy long-poll
mid-hold, and the access log now carries request duration - without it a
slow request is indistinguishable from a fast one and latency has to be
reconstructed from outside the container. Healthcheck moved off
POST /api/auth/login, which logged a 400 every 30s and exercised the
credential path from a probe.
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