"Cannot resolve type description" when class is not present

[bsideup]

Hi!

We received a bug report in BlockHound ( reactor/BlockHound#71 ) that looks more like a bug in ByteBuddy.

I was able to reproduce it with the following setup:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webflux</artifactId>
        <version>2.2.1.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>net.bytebuddy</groupId>
        <artifactId>byte-buddy</artifactId>
        <version>1.10.2</version>
    </dependency>

    <dependency>
        <groupId>net.bytebuddy</groupId>
        <artifactId>byte-buddy-agent</artifactId>
        <version>1.10.2</version>
    </dependency>
</dependencies>

public static void main(String[] args) throws Exception {
    Instrumentation instrumentation = ByteBuddyAgent.install();

    String testClass = "ch.qos.logback.classic.Logger";

    new AgentBuilder.Default()
            .with(RedefinitionStrategy.RETRANSFORMATION)
            .with(InitializationStrategy.NoOp.INSTANCE)
            .with((PoolStrategy) (classFileLocator, classLoader) -> new TypePool.Default(
                    new CacheProvider.Simple(),
                    classFileLocator,
                    TypePool.Default.ReaderMode.FAST
            ))
            .with(AgentBuilder.Listener.StreamWriting.toSystemError().withErrorsOnly())

            .type(it -> testClass.equals(it.getName()))
            .transform((builder, typeDescription, classLoader, javaModule) -> {
                return builder.visit(Advice.to(TestAdvice.class).on(named("callAppenders")));
            })
            .installOn(instrumentation);

    Class.forName(testClass);
}

public static class TestAdvice {
    @Advice.OnMethodEnter
    public static void onEnter() {
    }
}

It fails with this exception:

java.lang.IllegalStateException: Cannot resolve type description for org.slf4j.event.LoggingEvent

	at net.bytebuddy.pool.TypePool$Resolution$Illegal.resolve(TypePool.java:159)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$TokenizedGenericType.toErasure(TypePool.java:6241)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$GenericTypeToken$Resolution$Raw$RawAnnotatedType.of(TypePool.java:3412)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$GenericTypeToken$Resolution$Raw$RawAnnotatedType$LazyRawAnnotatedTypeList.get(TypePool.java:3511)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$GenericTypeToken$Resolution$Raw$RawAnnotatedType$LazyRawAnnotatedTypeList.get(TypePool.java:3456)
	at net.bytebuddy.pool.TypePool$Default$LazyTypeDescription$LazyMethodDescription$LazyParameterDescription.getType(TypePool.java:6994)
	at net.bytebuddy.description.method.ParameterDescription$AbstractBase.asToken(ParameterDescription.java:178)
	at net.bytebuddy.description.method.ParameterDescription$AbstractBase.asToken(ParameterDescription.java:128)
	at net.bytebuddy.description.method.ParameterList$AbstractBase.asTokenList(ParameterList.java:98)
	at net.bytebuddy.description.method.MethodDescription$AbstractBase.asToken(MethodDescription.java:825)
	at net.bytebuddy.description.method.MethodDescription$AbstractBase.asToken(MethodDescription.java:376)
	at net.bytebuddy.description.method.MethodList$AbstractBase.asTokenList(MethodList.java:70)
	at net.bytebuddy.dynamic.scaffold.InstrumentedType$Factory$Default$1.represent(InstrumentedType.java:364)
	at net.bytebuddy.ByteBuddy.rebase(ByteBuddy.java:851)
	at net.bytebuddy.agent.builder.AgentBuilder$TypeStrategy$Default$1.builder(AgentBuilder.java:2007)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$Transformation$Simple$Resolution.apply(AgentBuilder.java:10117)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.doTransform(AgentBuilder.java:10494)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:10457)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.access$1500(AgentBuilder.java:10223)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$Java9CapableVmDispatcher.run(AgentBuilder.java:10907)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$Java9CapableVmDispatcher.run(AgentBuilder.java:10845)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:10413)
	at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$ByteBuddy$ModuleSupport.transform(Unknown Source)
	at java.instrument/sun.instrument.TransformerManager.transform(TransformerManager.java:188)
	at java.instrument/sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:563)
	at java.base/java.lang.ClassLoader.defineClass1(Native Method)
	at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
	at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174)
	at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:802)
	at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:700)
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:623)
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:315)
	at reactor.SampleReactor.main(SampleReactor.java:39)

[raphw]

It's less a bug than it's a feature. "Optional types" is something several developers assume for the JVM to work due to it's implicit type resolution but for legally transforming a type, all signature type information needs to be available during instrumentation.

Byte Buddy requires all type information for a transformed type to be available but for ch.qos.logback.classic.Logger, it cannot find org.slf4j.event.LoggingEvent. It is the equivalent exception to:

Class.forName("ch.qos.logback.classic.Logger").getDeclaredMethods()

Introspection only works if the introspected types are available. The good news is that this does not break anything but only aborts the instrumentation of the incomplete type.

[bsideup]

The good news is that this does not break anything

Well, it does seem to break InstrumentationImpl.retransformClasses and every transformation we apply in BlockHound.

Would it be possible to add some graceful handling of such cases?
Extra points if only incomplete signatures will be ignored but other methods will still be instrumented

[raphw]

It should not and I cannot reproduce this behavior from the example either. I assume that you see this single log statement but otherwise, everything works as expected.

If a retransformation fails (due to an unhandled error typically), you can split batches by using for example: AgentBuilder.RedefinitionStrategy.Listener.BatchReallocator.splitting() which keeps errors to a minimum since failed batches will be resubmitted in a divide and conquer fashion by breaking down to single type batches with failing classes.

You can also suppress installation errors by AgentBuilder.InstallationListener.ErrorSuppressing.INSTANCE.

For ignoring methods with incomplete signatures, you could add a MethodGraph.Compiler that probes and drops those methods. It would be a rather expensive operation, though. Normally, types with incomplete signatures are only loaded by accident but cannot work properly anyways.

[bsideup]

@raphw

Sorry, I had a side effect that made me think that the whole instrumentation fails, so it is indeed only about logging.

However, adding AgentBuilder.InstallationListener.ErrorSuppressing.INSTANCE does not seem to make the statement disappear.

The error seems to happen when the class is being defined (initial classloading) and reported in ExecutingTransformer#transform:

byte-buddy/byte-buddy-dep/src/main/java/net/bytebuddy/agent/builder/AgentBuilder.java

Line 10466 in dcbdc13

listener.onError(typeName, classLoader, module, classBeingRedefined != null, throwable);

which goes directly to AgentBuilder.Listener.StreamWriting.toSystemError().withErrorsOnly()

[raphw]

That was what I expected.

The installation only fails when errors are not catched by Byte Buddy and illegal byte code is issued. This should never happen but can occasionally with very rare byte code combinations, typically when other Java agents are involved.

[raphw]

I assume the question is answered, therefore I am closing this.