Use TagExtractor for JDBC connection-info tags (canary)

[dougqh]

Draft — stacked on #11817 (the TagContributor/TagExtractor API). First real use of the API; the canary for dissolving the decorators.

Lifts JDBCDecorator's JDBC-specific pure field→tag connection tags (db.warehouse / db.schema / db.pool.name — the setTagIfPresent block in onConnection) into ConnectionInfoExtractor, a named singleton TagExtractor<DBInfo>, applied via the span-first span.setTags(dbInfo, ConnectionInfoExtractor.INSTANCE) at the single onConnection site (monomorphic → the JIT inlines it). Behavior-identical: the extractor makes the same three setTagIfPresent calls via the same helper (now on the extractor class).

Scope (deliberately minimal)

Bucket-(b) pure extraction only, JDBC-only, no shared-base change. DB_TYPE / user / instance / hostname stay in the decorator — db.user moves in #11823; instance/hostname feed service-name derivation, which awaits the declarative-derivation step.

Perf

Perf-neutral by construction — the tags moved here were already direct setTagIfPresent calls (not the megamorphic template-method dispatches), and the extractor is monomorphic → inlines → same code as before. The dispatch-reduction win (N→1) lives in the template methods (dbUser/dbInstance/dbHostname), addressed in the stacked peels. See the synthetic TagProjectionBenchmark in #11817 for the mechanism.

Validation

JDBCInstrumentationV0Test green (87/87, incl. the db.warehouse/db.schema/db.pool.name assertions). Notably, ConnectionInfoExtractor — a separate top-level helper class (the old lambda used to compile into JDBCDecorator) — is auto-injected via transitive helper collection with no helperClassNames() edit. (RemoteJDBC* tests are postgres/mysql/sqlserver testcontainers — env-gated, CI-only.)

🤖 Generated with Claude Code

[datadog-prod-us1-6]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 54.95% (+0.01%)

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[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	14.66 s	14.67 s	[-1.0%; +0.7%] (no difference)
startup:insecure-bank:tracing:Agent	13.34 s	13.60 s	[-2.6%; -1.2%] (significantly better)
startup:petclinic:appsec:Agent	16.96 s	17.32 s	[-3.1%; -1.0%] (maybe better)
startup:petclinic:iast:Agent	16.92 s	17.59 s	[-4.6%; -2.9%] (significantly better)
startup:petclinic:profiling:Agent	17.21 s	17.49 s	[-2.6%; -0.7%] (maybe better)
startup:petclinic:sca:Agent	17.15 s	17.42 s	[-2.5%; -0.5%] (maybe better)
startup:petclinic:tracing:Agent	16.33 s	16.71 s	[-3.3%; -1.3%] (significantly better)

Commit: 56d280df · CI Pipeline · Benchmarking Platform UI

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