The event-loop monitor starts first in register(), so loading the
database client and the worker graph is inside its view, and a stall line
now carries the process uptime, the startup phase, the boot step running
at the time and the oldest work in flight. Each boot step is timed, and
the boot ends with one boot.steps line.
The five registrars and the lifecycle helpers are imported one at a time
after boss.start(), with a turn of the event loop in between, instead of
all at once when the worker module loads. The longest stall is then the
largest registrar graph rather than the sum of all five.
Production showed multi-second windows where every response — routes,
RSC payloads, static assets — waited together while handler durations
stayed under half a second: the process stalled, and nothing
route-shaped could name it. A self-rescheduling tick now records how
late it fires; a tick past the stall threshold emits its own
event_loop_stall background event, and every wide event carries the
recent worst lag so the first request finishing after a stall is
annotated with it. Measured via a timeout chain rather than
perf_hooks.monitorEventLoopDelay — the histogram's sampling timer races
a sibling read-and-reset interval in the same timers phase and the
stall sample can vanish into the reset window.
Marc-André Bombeck