Class IndyBootstrap

java.lang.Object

io.opentelemetry.javaagent.tooling.instrumentation.indy.IndyBootstrap

public class IndyBootstrap
extends Object

We instruct Byte Buddy (via Advice.WithCustomMapping.bootstrap(java.lang.reflect.Method)) to dispatch non-inlined advices via an invokedynamic (indy) instruction. The target method is linked to a dynamically created instrumentation module class loader that is specific to an instrumentation module and the class loader of the instrumented method.

The first invocation of an INVOKEDYNAMIC causes the JVM to dynamically link a CallSite. In this case, it will use the bootstrap(MethodHandles.Lookup, String, MethodType, Object[]) method to do that. This will also create the InstrumentationModuleClassLoader.

  Bootstrap CL ←──────────────────────────── Agent CL
      ↑ └───────── IndyBootstrapDispatcher ─ ↑ ──→ └────────────── bootstrap(MethodHandles.Lookup, String, MethodType, Object[])
    Ext/Platform CL               ↑          │                        ╷
      ↑                           ╷          │                        ↓
    System CL                     ╷          │        IndyModuleRegistry.getInstrumentationClassLoader(String, ClassLoader)
      ↑                           ╷          │                        ╷
    Common               linking of CallSite │                        ╷
    ↑    ↑             (on first invocation) │                        ╷
WebApp1  WebApp2                  ╷          │                     creates
         ↑ - InstrumentedClass    ╷          │                        ╷
         │                ╷       ╷          │                        ╷
         │                INVOKEDYNAMIC      │                        ↓
         └────────────────┼──────────────────InstrumentationModuleClassLoader
                          └╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶╶→├ AdviceClass
                                                 ├ AdviceHelper
                                                 └ LookupExposer

Legend:
 ╶╶→ method calls
 ──→ class loader parent/child relationships

Method Summary

Modifier and Type	Method	Description
static void	emitIndyStaticCall(org.objectweb.asm.MethodVisitor mv, String name, String descriptor, Class<?> instrumentationModule, String helperClassDotName)	Emit invokedynamic instruction that will call the given helper class static method.
static Method	getIndyBootstrapMethod()

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

getIndyBootstrapMethod

public static Method getIndyBootstrapMethod()

emitIndyStaticCall

public static void emitIndyStaticCall(org.objectweb.asm.MethodVisitor mv,
 String name,
 String descriptor,
 Class<?> instrumentationModule,
 String helperClassDotName)

Emit invokedynamic instruction that will call the given helper class static method.