feat(instr): Phase 3 — INVOKEDYNAMIC handler isolation#830
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feat(instr): Phase 3 — INVOKEDYNAMIC handler isolation#830
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Replace INVOKESTATIC handler copying with INVOKEDYNAMIC dispatch so probe handler methods stay in the probe class (bootstrap CL) and are called via ConstantCallSite, eliminating bytecode copying into target classes. New: - IndyDispatcher: Java 8+ bootstrap method using publicLookup().findStatic() on the probe class; wired from HandlerRepositoryImpl's static initializer via reflection on IndyDispatcher.repository (volatile bridge field) - HandlerRepositoryImpl: rewrites resolveHandler() to return MethodHandle instead of byte[]; uses ConcurrentHashMap with UNRESOLVED sentinel for failed lookups; registerProbe() now evicts stale UNRESOLVED entries so late-resolving probes work after a registration race - DispatchBenchmark: JMH benchmark for ConstantCallSite dispatch overhead Deleted: - Indy.java (Java-15-specific defineHiddenClass bootstrap, no longer needed) - CopyingVisitor.java (handler bytecode copying, no longer needed) - static/ golden files (~198 files, replaced by unified dynamic/ files) Refactored: - Instrumentor.invokeBTraceAction: always emits INVOKEDYNAMIC; removed useHiddenClasses dual-mode gate; bootstrap handle owner: Indy → IndyDispatcher - Probe lifecycle symmetry: registerProbe() moved to BTraceProbeNode/ BTraceProbePersisted.register() (after defineClass); unregisterProbe() moved to both unregister() methods; removed premature registration in BTraceProbeFactory and redundant unregisterProbe in Client.onExit() - BTraceRuntimeImpl_9/_11: StackWalker frames filtered for org.openjdk.btrace.runtime.auxiliary.* to skip IndyDispatcher frames in getCallerClassLoader() and getCallerClass() - HandlerRepositoryImpl: dead probe.getClass() condition simplified to always load probe script from bootstrap CL (where it is defined) - IndyDispatcher: added diagnostic logging for handler resolution failures Test plan: ./gradlew :btrace-instr:test — all instrumentor tests pass ./gradlew :btrace-instr:test -PupdateTestData — 382 dynamic golden files regenerated Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Documents the develop-only branch model, build commands, module layout, and PR checklist so automated review sessions always target the correct integration branch. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
4 tasks
…ilure
IndyDispatcher lives in the bootstrap classloader. Adding SLF4J Logger
initialization to it caused LoggerFactory.getLogger() to run during
bootstrap class init, where no SLF4J provider is available. This made
Class.forName("...IndyDispatcher") throw ExceptionInInitializerError,
which HandlerRepositoryImpl's static initializer caught and swallowed —
leaving IndyDispatcher.repository null and all @OnMethod handlers as
permanent noops.
Handler resolution failures are already logged by HandlerRepositoryImpl
on the agent-classloader side. No logging is needed in the bootstrap
dispatcher itself.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…dispatch getBytecode(true) filtered to only BCP-required methods, which excluded @OnMethod handlers (isBcpRequired() returns false when om != null). The bootstrap-CL probe class therefore had no handler methods, causing IndyDispatcher → HandlerRepositoryImpl.resolveHandler() → publicLookup().findStatic() to throw NoSuchMethodException, which was caught and stored as UNRESOLVED, permanently installing a noop ConstantCallSite for every instrumented call site. Fix: also include methods where getOnMethod() != null in the bootstrap-CL class, and include their callees transitively. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…strap class The INDY call site descriptor (generated by Instrumentor.invokeBTraceAction) replaces AnyType with Object for JVM stack compatibility. The bootstrap-CL probe class must have matching method descriptors so that publicLookup().findStatic(probeClass, name, handlerType) succeeds. Without this, handlers using @return AnyType or AnyType[] parameters (oneliners with args, return-value captures, etc.) resolve as UNRESOLVED and get a permanent noop CallSite, silencing those probe points. Apply the same AnyType→Object descriptor substitution that copy() uses for handler bytecode sent to defineHiddenClass (the old Java-15 path). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…r lookup Two fixes: 1. BTraceProbeNode.getBytecode(true): also include @OnProbe handler methods (op != null) in the bootstrap-CL probe class. mapOnProbes() maps @OnProbe to synthetic @OnMethod entries which generate INDY call sites; the handler method bodies must be present in the bootstrap class for resolveHandler() to find them via findStatic(). 2. BTraceRuntimeImpl_8.getCallerClassLoader/getCallerClass: skip org.openjdk.btrace.runtime.auxiliary.* frames when walking the call stack, mirroring BTraceRuntimeImpl_9's StackWalker-based skip of those frames. Before this fix, the probe handler frame (in bootstrap CL) was counted as the application caller, causing Class.forName inside BTraceUtils.field() and similar reflection utilities to use the bootstrap CL and fail with ClassNotFoundException for application classes. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…trapClass On JDK 8, BTraceRuntimeImpl_8.isBootstrapClass() calls findBootstrapOrNullMtd.invoke() to check bootstrap classloader membership. After 15 invocations the JVM inflates the reflective accessor, creating sun/reflect/GeneratedMethodAccessorN via ClassLoader.defineClass(). This class-definition callback triggers BTraceTransformer.transform() which calls BTraceClassWriter.getCommonSuperClass() → ClassInfo.inferClassLoader() → isBootstrapClass() → invoke() again. At call count > 15 the JVM tries to inflate ANOTHER accessor (N+1), whose definition triggers another transform() → isBootstrapClass() → invoke() → accessor N+2, and so on indefinitely. The resulting StackOverflowError propagates out of agent initialization, causing testTraceAll (which instruments all classes via @OnMethod(clazz="/.*/")) to fail on JDK 8 with "FATAL: Initialization failed: StackOverflowError". Fix: add a ThreadLocal re-entrancy guard in isBootstrapClass(). While the guard is set (i.e., we are already inside a bootstrap check that triggered accessor inflation), any re-entrant call returns false conservatively. This breaks the infinite recursion; the accessor class is defined once and subsequent invoke() calls are served directly by the generated accessor. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
Replaces INVOKESTATIC handler copying with INVOKEDYNAMIC dispatch so probe handler methods stay in the probe class (bootstrap CL) and are called via
ConstantCallSite, eliminating bytecode copying into target classes. Works on Java 8+.Dispatch chain
New files
IndyDispatcher— Java 8+ bootstrap; resolves probe handler viapublicLookup().findStatic()on the probe class; wired toHandlerRepositoryImplvia avolatile HandlerRepository repositorybridge field set from the agent CL via reflectionHandlerRepositoryImpl(rewritten) —ConcurrentHashMapwithUNRESOLVEDsentinel for failed lookups;registerProbe()evicts stale UNRESOLVED entries to handle registration racesDispatchBenchmark— JMH benchmark comparing direct call baseline vsConstantCallSitedispatchDeleted
Indy.java— Java 15-specificdefineHiddenClassbootstrap, no longer neededCopyingVisitor.java— handler bytecode copying, no longer neededstatic/golden files (~198) — replaced by unifieddynamic/filesRefactored
Instrumentor.invokeBTraceAction— always emits INVOKEDYNAMIC; removeduseHiddenClassesdual-mode gate; bootstrap handle owner:Indy→IndyDispatcherregisterProbemoved toBTraceProbeNode/BTraceProbePersisted.register()(afterdefineClass);unregisterProbeadded to bothunregister()methods; removed premature registration inBTraceProbeFactoryand redundant cleanup inClient.onExitBTraceRuntimeImpl_9/_11— StackWalker frames filtered fororg.openjdk.btrace.runtime.auxiliary.*ingetCallerClassLoader()andgetCallerClass()BTraceClassWriter,BTraceTransformer, andInstrumentorTest plan
./gradlew :btrace-instr:test— all instrumentor tests pass./gradlew :btrace-instr:test -PupdateTestData— 382 dynamic golden files regenerated./gradlew :integration-tests:test -Pintegration— requires Docker (run separately)./gradlew :benchmarks:runtime-benchmarks:jmh -PjmhInclude=DispatchBenchmarkAcceptance criteria
static/golden files replaced with unifieddynamic/filesHandlerRepositoryImplTestverifies attach/detach cycle clears all handler cache entriesHandlerRepositoryImplusesConcurrentHashMapwithUNRESOLVEDsentinelDispatchBenchmarkexists🤖 Generated with Claude Code
This change is