Joseph Doherty ef53553e9d OTel Prometheus exporter wiring — RedundancyMetrics meter now scraped at /metrics. Closes task #201. Picked Prometheus over OTLP per the earlier recommendation (pull-based means no OTel Collector deployment required for the common K8s/containers case; the endpoint ASP.NET-hosts inside the Admin app already, so one less moving part). Adds two NuGet refs to the Admin csproj: OpenTelemetry.Extensions.Hosting 1.15.2 (stable) + OpenTelemetry.Exporter.Prometheus.AspNetCore 1.15.2-beta.1 (the exporter has historically been beta-only; rest of the OTel ecosystem treats it as production-acceptable + it's what the upstream OTel docs themselves recommend for AspNetCore hosts). Program.cs gains a Metrics:Prometheus:Enabled toggle (defaults true; setting to false disables both the MeterProvider registration + the scrape endpoint entirely for locked-down deployments). When enabled, AddOpenTelemetry().WithMetrics() registers a MeterProvider that subscribes to the "ZB.MOM.WW.OtOpcUa.Redundancy" meter (the exact MeterName constant on RedundancyMetrics) + wires AddPrometheusExporter. MapPrometheusScrapingEndpoint() appends a /metrics handler producing the Prometheus text-format output; deliberately NOT authenticated because scrape jobs typically run on a trusted network + operators who need auth wrap the endpoint behind a reverse-proxy basic-auth gate per fleet-ops convention. appsettings.json declares the toggle with Enabled: true so the default deploy gets metrics automatically — turning off is the explicit action. Future meters (resilience tracker + host status + auth probe) just AddMeter("Name") alongside the existing call to start flowing through the same endpoint without more infrastructure. Admin project builds 0 errors; Admin.Tests 92/92 passing (unchanged — the OTel pipeline runs at request time, not test time). Still-pending work that was NOT part of #201's scope: an equivalent setup for the Server project (different MeterNames — the Polly pipeline builder's tracker + host-status publisher) + a metrics cheat-sheet in docs/observability.md documenting each meter's tag set + expected alerting thresholds. Those are natural follow-ups when fleet-ops starts building dashboards. ...

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-04-20 00:41:16 -04:00

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