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…ndSafe / @BackgroundOnly DDCache is cheap (small, bounded probe count) -- safe to call from application threads. SimpleUtf8Cache and GenerationalUtf8Cache trade CPU for allocation savings that only pay off when run on a background thread, so they're confined to the background serializer thread. APMLP-1544 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
The prior commit documented the constraint in a Javadoc @link but never applied the annotation itself, so J16's grep-based resolution had nothing to match. APMLP-1544 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Add the Checker contract section (Trigger/Not-a-trigger/Violation/ Compliant/Out-of-scope) that @NoEscape already uses, so the rule is machine-checkable straight from the annotation's own Javadoc without needing J16's prose. Also note that @BackgroundOnly is orthogonal to JSR-305 @threadsafe -- one governs concurrent-caller safety, the other which category of caller is valid at all -- since both now land on the same cache classes. APMLP-1543 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
…16 test coverage Adds the declaration-site inheritance-narrowing rule to both annotations' Javadoc and to the performance lens's J16 addendum (now slugged background-only-contract for stable cross-referencing), switches both annotations from SOURCE to CLASS retention so a future bytecode checker (APMLP-1645) can see them, adds llm-validation fixtures covering the interface-hop and inheritance-widening cases, and documents the foreground/background contract in instrumentation_design_guidelines.md. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
…lse-positive FixedSizeCache's @ForegroundSafe Javadoc overclaimed: computeIfAbsent's producer and visit()'s consumer are caller-supplied and can be arbitrarily expensive, so the annotation now scopes its guarantee to the cache's own bookkeeping only. J16's interface-propagation hop-1 flagged any interface-typed call site reachable to a @BackgroundOnly implementer C, even when the diff visibly binds the receiver to a different, safe implementation -- guaranteed unreachable. Hop-1 now checks for a visible binding first and only falls back to flag-with-confidence when the receiver's concrete type isn't resolvable from the diff. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
FixedSizeCache's per-method markers were unreachable by the checker at real call sites, since every caller holds a DDCache-typed reference. Move @BackgroundOnly onto DDCache.visit() itself (mirroring the EncodingCache precedent) and drop it from FixedSizeCache.clear(), which wasn't cost-justified at the small capacities real callers use. Also fixes an inverted "narrow"/"widen" phrase in both markers' javadoc (three independent reviewers flagged it) and updates the J16 example in performance.md to match.
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What Does This Do
datadog.trace.api.function.ForegroundSafe/.BackgroundOnlyannotations declaring a one-way foreground/background cost contract.@BackgroundOnly/@ForegroundSafetoDDCache,FixedSizeCache,EncodingCache,SimpleUtf8Cache, andGenerationalUtf8Cacheas initial markers.docs/instrumentation_design_guidelines.md.CLASSretention so a future bytecode-level checker (APMLP-1645) can consume the markers.Motivation
Part of APMLP-1513 / APMLP-1645: giving a declared contract to check foreground/background thread-cost assumptions against, rather than relying on ad hoc judgment calls about whether code is cheap enough for a foreground thread.
Notes
dd-apm-sdk-reviewreview-framework branch). The J16 checker-lens rule and.llm-validationfixtures that accompanied that work are dropped from this PR along with the framework dependency; checker enforcement is deferred to APMLP-1645 and, if useful, to the/perf-reviewskill instead../gradlew :internal-api:spotlessJavaCheckpasses.Contributor Checklist
type:and (comp:orinst:) labels in addition to any other useful labelsclose,fix, or any linking keywords when referencing an issueJira ticket: APMLP-1513
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