New subcommand drives the gateway''s StreamEvents server-stream as fast
as it can from a single client process. Subscribes to --bulk-size tags
(rotating through all six TestMachine attributes by default) and counts
events received over a --duration-seconds steady-state window. Tracks
events/sec, end-to-end latency (now - event.worker_timestamp), and any
worker faults observed via a post-run DrainEvents probe.
--session-count opens N independent gateway sessions from the same
client process — each session is independent at the gateway (own
worker, own event subscriber, own item handles) so this measures how
the gateway multiplexes concurrent event streams without needing
multiple client processes. Sessions are staggered open by default
(--session-start-stagger-ms 750) because firing N concurrent
OpenSession calls forces N concurrent worker x86 spawns, and on a dev
rig that exceeds the gateway''s 30-second worker startup timeout
around N >= 6-8. The stagger gives each worker headroom to init its
COM apartment + attach the event sink before the next one starts.
Phase 1 of the bench opens + subscribes every session sequentially;
phase 2 opens the steady-state window once everyone is advised, so
the measurement isn''t skewed by late-arriving sessions still in
warmup. The latency sample is shared across sessions (locked
List<double>); event counts use Interlocked.
Initial sweep at --bulk-size 120 against the dev galaxy (20 machines
x 6 attributes = 120 unique tags) showed:
- Linear throughput scaling with subscribed-tag count: N=6→2 ev/s,
N=24→8 ev/s, N=60→20 ev/s, N=120→41 ev/s. The dev galaxy is
producer-bound at ~0.34 events/sec per advised tag — gateway has
plenty of headroom.
- Latency stayed at p50 ≈17ms, p95 ≈34ms across the entire range —
no degradation with subscribed-tag count.
- Zero queue-overflow faults; gateway 10k-event buffer never came
close to filling at this producer rate.
- Linear scaling with session count too (staggered open): 1→44, 2→81,
4→130, 8→324 events/sec at p50 16ms across all session counts.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Joseph Doherty
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