Story 15.3: JOIN query counter — TelemetryCollector buckets + TelemetryData delta

[fupelaqu]

Story 15.3 — JOIN query counter (elasticsql / licensing)

Part of Epic 15 (telemetry). Adds a per-interval, disaggregated cross-index JOIN counter to the runtime telemetry layer so the Story-15.2 daily product-instance ping can carry a join_query_count delta, and the R1 dashboard (Story 15.5) can show how much JOIN workload R1 runs — with NO PII (integer counters only).

Scope (this repo — licensing module)

• TelemetryCollector.scala:
  • JoinRow enum (Passthrough row 1 / CrossCluster row 2 / Coordinator row 3)
  • 3 AtomicLong buckets + incrementJoin(JoinRow) (lock-free, mirrors incrementQueries)
  • collectAndResetJoinCounts(): (Long, Map[String,Long]) helper (returns total + all-3-keys map)
  • extended collect (read .get(), NO reset) and collectAndReset (read .getAndSet(0L), per-interval delta flush)
  • TelemetryData gains joinQueryCount: Long (total) + joinQueryByRow: Map[String,Long] (always all 3 keys, even when 0)
  • TelemetryCollector.Noop overrides incrementJoin (no-op) and collectAndResetJoinCounts (zeros, all 3 keys)
• Scaladoc updated: JOIN fields are per-interval DELTAS (reset each collectAndReset), distinct from the cumulative queriesTotal (left unchanged).

Behaviour

• joinQueryCount == passthrough + cross_cluster + coordinator on every collected snapshot.
• collect never resets; collectAndReset/collectAndResetJoinCounts reset (per-interval delta + clean-shutdown flush).
• No SQL text, no org/query identifiers — only integers (AC 7).

Tests

8 new TelemetryCollectorSpec cases: per-row increment + total, all-3-keys-always (incl. 0), collect-no-reset, collectAndReset-reset, collectAndResetJoinCounts reset (and queriesTotal unaffected), concurrent increment, no-PII, Noop no-op. 16/16 pass.

Build

scalafmtAll; + licensing/compile + + core/compile clean (Scala 2.12.20 + 2.13.16).

The increment hooks live downstream in softclient4es-arrow (sidecar/federation/REPL) and the AC-5a disabled-tick reset in softclient4es-extensions; this repo owns the counter carrier + delta exposed on TelemetryData.

Spec: _bmad-output/implementation-artifacts/15-3-join-query-counter.md

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