test(loadharness)+docs: wire-path stream probes — R2 batching benchmark-proven at target scale

The WP-4 runs measured the stream path only up to the bounded send channel; the probe deliberately substituted the socket hop with a controllable reader, which is exactly where the R2 SiteStreamEventBatcher lives — so batching had never been in any benchmark's hot path. The harness now also attaches per-site wire probes: a real Kestrel h2c listener hosting the production SiteStreamGrpcServer, dialed by the production SiteStreamGrpcClient with batching negotiated, batch sizes read from the production batch_size histogram via a MeterListener (--wire-probes-per-site, default 10; 0 restores the old shape). Full-scale run (10x500x75, 20-min window, results doc §8 + raw JSON): 899,807 events in 12,462 frames (mean 72.2 ev/frame, p50=p99=75), wire P99 43.4 ms vs the 250 ms budget — every batch pays the full 25 ms linger since a 75-event burst never hits the 100 cap — zero drops, zero faults, offered load 100.0% of nominal with fan-out doubled. CI smoke Fact now asserts the wire path carries traffic and observes frames.
2026-08-18 10:32:46 -04:00
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@@ -191,7 +191,7 @@ Each is a deliberate, recorded trade — not an omission.
 | D1 | **Sustained window shortened from 1 hour to 20 minutes** at full scale | Practicality on a single shared workstation. Memory growth is reported as a *slope* precisely so a shorter window still answers the leak question: a leak shows as a positive slope in 20 min just as in 60. The 1-hour run is a single flag — `--sustain-minutes 60` — and the exact command is recorded in the results doc. |
 | D2 | **In-process, non-clustered sites** rather than 10 real two-node Akka clusters | A single box cannot host 20 clustered nodes at this scale. Cluster membership/failover is already measured on a real two-node rig (`FailoverTimingTests`, `docker/failover-drill.sh`); WP-4's question is about the hierarchy under the singleton. |
 | D3 | **Simulated data source** instead of real OPC UA | No simulated adapter exists in the DCL, and 375k real monitored items would measure the OPC UA SDK. Injected at the documented `RegisterAdapter` seam, at the exact hand-off point the real adapter uses. |
-| D4 | **gRPC socket replaced by a reader task** on the stream path | Required by the row-50 measurement itself: a stalled subscriber must be *held* stalled. All of `SiteStreamGrpcServer`'s per-subscription machinery above the socket is real. |
+| D4 | **gRPC socket replaced by a reader task** on the stream path | Required by the row-50 measurement itself: a stalled subscriber must be *held* stalled. All of `SiteStreamGrpcServer`'s per-subscription machinery above the socket is real. **Partially retired 2026-08-18:** the harness now ALSO attaches per-site wire probes — real Kestrel h2c + real `SiteStreamGrpcClient` with R2 batching negotiated (`--wire-probes-per-site`, default 10) — so the batcher/serialization/HTTP/2 hop is measured too; the substituted-reader probes remain because the slow-subscriber scenario still needs them. Results doc §8. |
 | D5 | **Instance Actors are `/user` children**, not children of a `DeploymentManagerActor` | Constructing them directly is what lets the ramp be timed in isolation and keeps the harness independent of the deploy round-trip. Visible only as `InstanceActorInitialized` dead letters, which the harness suppresses. No measured path differs. |
 | D6 | **Akka logging at WARNING** | At 37,500 updates/s, INFO output would itself become a measured load. |
 | D7 | `[xc-3]` site event logging volume, `[xc-4]` audit-log degradation, `[xc-5]` template flattening, `[xc-8]` UI responsiveness **not covered** | Out of scope for this harness: the first three need central MS SQL and the Template Engine (a central-cluster fixture, not a site one), and `[xc-8]` needs a browser. Recorded as residual scope in the results doc rather than silently dropped. |