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Use VirtualField for associating netty listener with wrapper #5282

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Jan 31, 2022
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
package io.opentelemetry.javaagent.instrumentation.internal.lambda;

import io.opentelemetry.javaagent.bootstrap.ClassFileTransformerHolder;
import io.opentelemetry.javaagent.bootstrap.InjectedHelperClassDetector;
import java.lang.instrument.ClassFileTransformer;

/** Helper class for transforming lambda class bytes. */
Expand All @@ -29,6 +30,11 @@ private static boolean isJava9() {
*/
@SuppressWarnings("unused")
public static byte[] transform(byte[] classBytes, String slashClassName, Class<?> targetClass) {
// Skip transforming lambdas of injected helper classes.
if (InjectedHelperClassDetector.isHelperClass(targetClass)) {
return classBytes;
}

ClassFileTransformer transformer = ClassFileTransformerHolder.getClassFileTransformer();
if (transformer != null) {
try {
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -11,25 +11,25 @@
import io.netty.util.concurrent.ProgressiveFuture;
import io.opentelemetry.context.Context;
import io.opentelemetry.context.Scope;
import io.opentelemetry.instrumentation.api.cache.Cache;
import io.opentelemetry.instrumentation.api.field.VirtualField;
import java.lang.ref.WeakReference;

public final class FutureListenerWrappers {
// note: it's ok if the value is collected prior to the key, since this cache is only used to
// remove the wrapped listener from the netty future, and if the value is collected prior to the
// key, that means it's no longer used (referenced) by the netty future anyways.
//
// also note: this is not using VirtualField in case this is ever converted to library
// instrumentation, because while the library implementation of VirtualField maintains a weak
// reference to its keys, it maintains a strong reference to its values, and in this particular
// case the wrapper listener (value) has a strong reference to original listener (key), which will
// create a memory leak. which is not a problem in the javaagent's implementation of VirtualField,
// since it injects the value directly into the key as a field, and so the value is only retained
// strongly by the key, and so they can be collected together.
private static final Cache<
// also note: this is using WeakReference as VirtualField value in case this is ever converted to
// library instrumentation, because while the library implementation of VirtualField maintains a
// weak reference to its keys, it maintains a strong reference to its values, and in this
// particular case the wrapper listener (value) has a strong reference to original listener (key),
// which will create a memory leak. which is not a problem in the javaagent's implementation of
// VirtualField, since it injects the value directly into the key as a field, and so the value is
// only retained strongly by the key, and so they can be collected together.
private static final VirtualField<
GenericFutureListener<? extends Future<?>>,
WeakReference<GenericFutureListener<? extends Future<?>>>>
wrappers = Cache.weak();
wrapperVirtualField = VirtualField.find(GenericFutureListener.class, WeakReference.class);

private static final ClassValue<Boolean> shouldWrap =
new ClassValue<Boolean>() {
Expand All @@ -54,7 +54,7 @@ public static GenericFutureListener<?> wrap(
// collected before we have a chance to make (and return) a strong reference to the wrapper

WeakReference<GenericFutureListener<? extends Future<?>>> resultReference =
wrappers.get(delegate);
wrapperVirtualField.get(delegate);

if (resultReference != null) {
GenericFutureListener<? extends Future<?>> wrapper = resultReference.get();
Expand All @@ -75,14 +75,14 @@ public static GenericFutureListener<?> wrap(
} else {
wrapper = new WrappedFutureListener(context, (GenericFutureListener<Future<?>>) delegate);
}
wrappers.put(delegate, new WeakReference<>(wrapper));
wrapperVirtualField.set(delegate, new WeakReference<>(wrapper));
return wrapper;
}

public static GenericFutureListener<? extends Future<?>> getWrapper(
GenericFutureListener<? extends Future<?>> delegate) {
WeakReference<GenericFutureListener<? extends Future<?>>> wrapperReference =
wrappers.get(delegate);
wrapperVirtualField.get(delegate);
if (wrapperReference == null) {
return delegate;
}
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
/*
* Copyright The OpenTelemetry Authors
* SPDX-License-Identifier: Apache-2.0
*/

package io.opentelemetry.javaagent.bootstrap;

import java.util.function.Function;

/** Helper class for detecting whether given class is an injected helper class. */
public final class InjectedHelperClassDetector {

private InjectedHelperClassDetector() {}

private static volatile Function<Class<?>, Boolean> helperClassDetector;

/** Sets the {@link Function} for detecting injected helper classes. */
public static void internalSetHelperClassDetector(
Function<Class<?>, Boolean> helperClassDetector) {
if (InjectedHelperClassDetector.helperClassDetector != null) {
// Only possible by misuse of this API, just ignore.
return;
}
InjectedHelperClassDetector.helperClassDetector = helperClassDetector;
}

public static boolean isHelperClass(Class<?> clazz) {
if (helperClassDetector == null) {
return false;
}
return helperClassDetector.apply(clazz);
}
}
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
import io.opentelemetry.instrumentation.api.cache.Cache;
import io.opentelemetry.javaagent.bootstrap.DefineClassContext;
import io.opentelemetry.javaagent.bootstrap.HelperResources;
import io.opentelemetry.javaagent.bootstrap.InjectedHelperClassDetector;
import io.opentelemetry.javaagent.tooling.muzzle.HelperResource;
import java.io.File;
import java.io.IOException;
Expand Down Expand Up @@ -50,6 +51,10 @@ public class HelperInjector implements Transformer {
private static final TransformSafeLogger logger =
TransformSafeLogger.getLogger(HelperInjector.class);

static {
InjectedHelperClassDetector.internalSetHelperClassDetector(HelperInjector::isInjectedClass);
}

// Need this because we can't put null into the injectedClassLoaders map.
private static final ClassLoader BOOTSTRAP_CLASSLOADER_PLACEHOLDER =
new SecureClassLoader(null) {
Expand Down