Migrate context bridge to the all-native DDProf API (Phase 2)

[rkennke]

What

Migrates the profiler context bridge off the deprecated DirectByteBuffer (DBB) context API onto java-profiler's all-native API (setTraceContext / clearTraceContext / setContextValue / clearContextValue).

This is Phase 2 of the all-native context work (Phase 1 = DataDog/java-profiler#631).

Why

• Fixes the virtual-thread use-after-free: the DBB path cached a DirectByteBuffer over the native OTEP record; on a carrier that a mounted virtual thread later migrated off, the record was freed while the cached buffer kept being written. The all-native API resolves the current carrier's record inside each JNI call — no cached buffer to dangle.
• Per-activation perf: activation collapses from setContext + 2×setContextValue (3 JNI calls) into one setTraceContext (~28% faster on the combined cycle per the design-note benchmark).

Changes

• DatadogProfilingIntegration.activate → one setTraceContext(...) carrying trace/span context + operation & resource attributes; close/clearContext → clearTraceContext().
• DatadogProfiler: setContextValue/clearContextValue/reapplyAppContext/syncNativeAppContext are now all-native. reapplyAppContext uses a per-slot native setContextValue loop — native setContextValue publishes the record (valid=1) even with no active span, so app context stays visible between spans (preserves Restore app context attributes wiped by ddprof setContext on span activation #11646). A native batch reapply is deferred to a measured follow-up (java-profiler PROF-15361).
• AppContextSnapshot simplified to strings-only (the native path resolves each value's encoding via the process-wide cache — no cached id/utf8/snapshotTags DBB read).
• snapshot() uses the new native copyContextTags read (no ThreadContext/DBB, so it observes native writes without resetting the record).
• ContextSetter kept only for offsetOf + size (pure Java); no DBB usage remains.

Behavior notes

• Per-slot reapply is not atomic across app attributes. reapplyAppContext publishes each app-managed attribute with its own native setContextValue (detach→attach), so a profiler sample landing mid-reapply can observe a partial app-attribute set on activation — a window the old batch fast-path (setContextValuesByIdAndBytes, single attach) did not have. This is deliberate for the expected small app-attribute cardinality (0–2); the single-call batch reapply is the measured follow-up (PROF-15361). Trace/span + operation/resource stay atomic (one setTraceContext).
• Defensive zero-span guard. The native setTraceContext rejects spanId==0 (it is the activation path; clearing is clearTraceContext). Span ids are non-zero by construction (IdGenerationStrategy never yields 0, DDSpanId.ZERO means "no span", and DDSpanContext is the only ProfilerContext), so the bridge routes a stray zero span to clearTraceContext() rather than letting the IllegalArgumentException be swallowed over stale context.

Dependency

Requires java-profiler's all-native API, from DataDog/java-profiler#631. Master now pins ddprof = 1.47.0 (#12055), which includes it, so this branch has been rebased and builds against the published release — no local snapshot needed.

Status / verification

• Rebased onto master with the published ddprof:1.47.0 (Bump java-profiler (ddprof) to 1.47.0 #12055); compiles clean (no cannot find symbol on the new calls) and the profiling-ddprof unit test suite is GREEN on Linux post-rebase.
• Re-verified GREEN on Linux against the genuinely published ddprof:1.47.0 release (native lib extracted from the published jar, not a local snapshot): dd-smoke-tests:profiling-integration-tests (CodeHotspotsTest, JFRBasedProfilingIntegrationTest) — 20 tests, 2 skipped (both pre-existing/expected), 0 failures, 0 errors (end-to-end agent + profiler + JFR, exercising span/op/resource context).
• Two correctness bugs surfaced by automated PR review (stale-value resurrection on a rejected setContextValue, and reapplyAppContext overwriting freshly-written operation/resource values) were fixed and covered by new regression assertions in DatadogProfilerTest, each confirmed to fail without its corresponding fix.

🤖 Generated with Claude Code

[datadog-prod-us1-5]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 57.70% (-0.00%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 3668c1f | Docs | Datadog PR Page | Give us feedback!}

[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	13.95 s	13.93 s	[-0.5%; +0.8%] (no difference)
startup:insecure-bank:tracing:Agent	12.97 s	12.95 s	[-0.4%; +0.8%] (no difference)
startup:petclinic:appsec:Agent	16.72 s	16.77 s	[-1.3%; +0.7%] (no difference)
startup:petclinic:iast:Agent	16.81 s	16.89 s	[-1.5%; +0.6%] (no difference)
startup:petclinic:profiling:Agent	16.70 s	16.64 s	[-0.6%; +1.3%] (no difference)
startup:petclinic:sca:Agent	16.24 s	16.73 s	[-7.3%; +1.6%] (no difference)
startup:petclinic:tracing:Agent	15.89 s	15.68 s	[-3.0%; +5.8%] (no difference)

Commit: 3668c1fd · CI Pipeline · Benchmarking Platform UI

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[datadog-prod-us1-5]

Replacing an existing profiling context value with a >255-byte string now clears the native slot but retains its Java snapshot; the next span activation resurrects the stale prior value. The DBB base path retains the prior value continuously, so samples can lose and later regain incorrect context across this migration.

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[jbachorik]

Looks good. Just a small nit regarding naming.

[dd-octo-sts]

/merge

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-07-28 14:49:18 UTC ℹ️ Start processing command /merge

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2026-07-28 14:49:23 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in master is approximately 1h (p90).

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2026-07-28 16:08:05 UTC ℹ️ MergeQueue: This merge request was merged