Performance: @ThreadLocal annotated bean causes ClassUtils.forName() upon every access.

[patrickmhaller]

Expected Behavior

Access to thread-local values should be typically as fast as possible and avoid expensive operations, such as proxy bean creation or invoking a ClassLoader. The observed repetitive call to io.micronaut.core.reflect.ClassUtils.forName() on every access to a @ThreadLocal bean method seems unintentional to me.

I would have assumed accesses to @ThreadLocal annotated beans to perform comparably to classic java.lang.ThreadLocal. However, using a classic java.lang.ThreadLocal is significantly faster.

AbstractInitializableBeanDefinition.getScope() has a specific optimization for SINGLETON_SCOPE. Possibly similar is conceivable for @ThreadLocal. Or hopefully the generated $DateUtils$Definition$Intercepted.getStdDateFormat()
could avoid the whole getProxyTargetBean() chain entirely.

Actual Behaviour

Referring to below example code, every access to the injected @ThreadLocal annotated bean via
dateUtils.getStdDateFormat();
attempts to

• DefaultApplicationContext(DefaultBeanContext).getProxyTargetBean
• DefaultApplicationContext(DefaultBeanContext).findCustomScope
• eventually load "io.micronaut.runtime.context.scope.ThreadLocal.class" from the ClassLoader.

Steps To Reproduce

Given a minimal bean

@io.micronaut.runtime.context.scope.ThreadLocal
public class DateUtils {

	private final StdDateFormat stdDateFormat = new StdDateFormat();

	public DateFormat getStdDateFormat() {
		return stdDateFormat;
	}
}

consumed via

	@Inject
	DateUtils dateUtils;
	
	DateFormat df = dateUtils.getStdDateFormat();

sees the sequences of logs like

2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Attempting to dynamically load class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Successfully loaded class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Attempting to dynamically load class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Successfully loaded class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Attempting to dynamically load class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Successfully loaded class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Attempting to dynamically load class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Successfully loaded class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Attempting to dynamically load class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Successfully loaded class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Attempting to dynamically load class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Successfully loaded class io.micronaut.runtime.context.scope.ThreadLocal
2024-10-31 00:47:42 [default-nioEventLoopGroup-1-4] DEBUG i.micronaut.core.reflect.ClassUtils - Attempting to dynamically load class io.micronaut.runtime.context.scope.ThreadLocal

if debug logging is configured for io.micronaut.core.reflect.ClassUtils.

Note that the invocations are all on the same thread.

Stacktrace

Thread [pool-2-thread-1] (Suspended (breakpoint at line 276 in ClassUtils))	
	ClassUtils.forName(String, ClassLoader) line: 276	
	$DateUtils$Definition(AbstractInitializableBeanDefinition<T>).lambda$getScope$0(String) line: 311	
	0x00007fbf4c3aa9a0.apply(Object) line: not available	
	Optional<T>.flatMap(Function<? super T,Optional<? extends U>>) line: 289	
	$DateUtils$Definition(AbstractInitializableBeanDefinition<T>).getScope() line: 307	
	DefaultApplicationContext(DefaultBeanContext).findCustomScope(BeanResolutionContext, BeanDefinition<T>, boolean, boolean) line: 3033	
	DefaultApplicationContext(DefaultBeanContext).resolveBeanRegistration(BeanResolutionContext, BeanDefinition<T>, Argument<T>, Qualifier<T>) line: 3005	
	DefaultApplicationContext(DefaultBeanContext).getProxyTargetBean(BeanResolutionContext, BeanDefinition<T>, Argument<T>, Qualifier<T>) line: 1505	
	$DateUtils$Definition$Intercepted.interceptedTarget() line: not available	
	$DateUtils$Definition$Intercepted.getStdDateFormat() line: not available	
	GridRepository.writeLiveMeasurement(IEvent<Named,String>, JsonNode) line: 304	
...

with
name "io.micronaut.runtime.context.scope.ThreadLocal" (id=179)
classLoader ClassLoaders$AppClassLoader (id=103)

Environment Information

• Operating System: Gentoo Linux
• JDK: openjdk 21.0.5 2024-10-15 LTS
  OpenJDK Runtime Environment Temurin-21.0.5+11 (build 21.0.5+11-LTS)
  OpenJDK 64-Bit Server VM Temurin-21.0.5+11 (build 21.0.5+11-LTS, mixed mode, sharing)
• Micronaut 4.6.3

Example Application

n/a

Version

4.6.3

[graemerocher]

the class loading lookups shouldn't be needed