feat: Add feature_service label to Feature Server RED metrics #6639

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1. saket3395 commented on Aug 14, 2026

   

   saket3395

   on Aug 14, 2026

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   @jyejare @ntkathole I'd like to pick this up (following on from #6709). I read through metrics.py / feature_server.py and the existing feature_count/feature_view_count plumbing, and the pieces line up nicely — GetOnlineFeaturesRequest already carries feature_service, and the /get-online-features handler already owns a mutable RequestMetricsContext. Before I write it, I'd like to confirm the design so I build the version you want:

   Proposed implementation (mirrors the existing pattern):

   1. Add feature_service to RequestMetricsContext.__slots__ and to the track_request_latency(...) signature (default ""), exactly like feature_count/feature_view_count.
   2. Add a feature_service label to request_latency (and request_count) — gated so it's only populated when the opt-in flag is on; "" otherwise.
   3. In the /get-online-features handler, set metrics_ctx.feature_service = request.feature_service or "" (the name is already on the parsed request body — no extra lookup needed).
   4. Add an opt-in flag to MetricsConfig + _MetricsFlags (build_metrics_flags), default off, since a per-service label on the request_latency Histogram multiplies series and unbounded service cardinality could hurt large deployments.

   Design questions I'd like your call on before coding:

   • Flag name / shape: a dedicated request_feature_service boolean under MetricsConfig, or a sub-toggle nested under the existing request category? Happy to match whatever convention you prefer.
   • Which metrics get the label: request_latency for sure. Also add it to request_count? And do you want it on online_features_status_total (the track_feature_statuses path) in this same PR, or keep that out of scope for now?
   • Allowlist: the issue mentions an optional feature-service allowlist for cardinality control. I'd suggest shipping the opt-in boolean first (smaller, reviewable PR) and doing the allowlist as a follow-up — unless you'd rather have it in v1.

   Once you confirm the flag shape + metric scope, I'll open a PR with tests. Thanks!