Files
Marc Schier 04f3d12fa8 [security] Bound the participant metric tag to per-kind cardinality (MEDIUM-4)
plans/security-assessment.md MEDIUM-4 (unbounded metric cardinality):

opcua.channel.participant.timeout.count and
opcua.channel.participant.recreate.count emit a "participant" tag
whose value was the full per-instance IReconnectParticipant.Id. Two
problems:
  - ClientChannelReconnectParticipant uses
    "{idPrefix}-{Guid.NewGuid():N}" — the suffix made every instance
    permanent in cardinality-retaining metric backends (Prometheus,
    OTLP, Application Insights).
  - Session.ChannelManager.cs:45 used a bare Guid with NO prefix at
    all, so the metric tag was a 32-hex-char string with no way for
    operators to bucket the data.

Fix:
  - Session.ChannelManager.cs:45 — prefix the GUID with "Session-" so
    Session participants follow the same prefix-then-suffix shape as
    ClientChannelReconnectParticipant.
  - ClientChannelManagerMetrics — add a GetParticipantKind helper
    that returns everything before the first '-' (or the full id if
    no '-'). Use it in CreateEndpointParticipantTags and
    CreateEndpointParticipantSuccessTags so the metric tag stays at
    per-kind cardinality ("Session", "Client", …).
  - Full per-instance id continues to flow through Activity tags and
    EventSource events (separate code path in
    ClientChannelManagerDiagnostics) so distributed traces remain
    correlatable.
  - Docs/Sessions.md callout updated to describe the now-bounded
    behavior (was a warning before, now describes the implemented
    semantic and the convention required of custom participants).

Build verified: Stack/Opc.Ua.Core, Libraries/Opc.Ua.Client net10.0 —
0 W, 0 E.
2026-06-11 12:26:54 +02:00
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