feat: add outcome logging for tenant pools

[ferhatelmas]

What kind of change does this PR introduce?

feat

What is the current behavior?

Tenant pool cache hit ratio is an aggregate metric. We can't see tenant distribution.

What is the new behavior?

Adding tenant for metric isn't feasible due to high cardinality so we log its outcome.

Additional context

There are two knobs for hits & misses to adjust sampling ratio. Ideally, we can do no sampling for miss since rare but sample hits. By default, they start with full sampling (no logs).

Pool cache tests are moved to vitest.

[Copilot]

Pull request overview

Adds tenant-level outcome logging for tenant pool cache lookups (hit/miss/stale) as an alternative to high-cardinality tenant metrics, with configurable sampling via environment variables.

Changes:

• Introduces sampled logging for tenant pool cache lookups in PoolManager.getPool().
• Adds two new config knobs to control hit/miss log sampling rates and clamps env values to [0, 1].
• Adds Jest and Vitest coverage to validate logging behavior and sample-rate parsing.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/internal/database/pool.ts	Logs tenant pool cache lookup outcomes with sampling controls.
src/config.ts	Adds config fields + env parsing helper for log sample rates.
src/test/pool-cache.test.ts	Adds Jest tests covering lookup logging and sampling enable/disable behavior.
src/config.test.ts	Adds Vitest tests ensuring env sample-rate parsing/clamping behavior.

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[coveralls]

Coverage Report for CI Build 24402681358

Coverage increased (+0.06%) to 82.476%

Details

• Coverage increased (+0.06%) from the base build.
• Patch coverage: 1 uncovered change across 1 file (45 of 46 lines covered, 97.83%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
src/internal/database/pool.ts	27	26	96.3%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	33945
Covered Lines:	30460
Line Coverage:	89.73%
Relevant Branches:	7443
Covered Branches:	3675
Branch Coverage:	49.38%
Branches in Coverage %:	Yes
Coverage Strength:	347.57 hits per line

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💛 - Coveralls

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

---

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