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Support instrumentation for Executors.newVirtualThreadPerTaskExecutor() #6008

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Merged
merged 3 commits into from
Mar 17, 2025
Merged

Support instrumentation for Executors.newVirtualThreadPerTaskExecutor() #6008

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2ad60b4
Support instrumentation for Executors.newVirtualThreadPerTaskExecutor()
izeye Mar 11, 2025
d99f984
Remove accidental Awaitility dependency
izeye Mar 12, 2025
e5d159b
Replace Method with MethodHandle for ThreadPerTaskExecutor.threadCount()
izeye Mar 13, 2025
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10 changes: 6 additions & 4 deletions ...r-core/src/main/java/io/micrometer/core/instrument/binder/jvm/ExecutorServiceMetrics.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,8 @@
import io.micrometer.core.instrument.internal.TimedExecutorService;
import io.micrometer.core.instrument.internal.TimedScheduledExecutorService;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.List;
Expand Down Expand Up @@ -60,7 +62,7 @@ public class ExecutorServiceMetrics implements MeterBinder {
private static final String CLASS_NAME_THREAD_PER_TASK_EXECUTOR = "java.util.concurrent.ThreadPerTaskExecutor";

@Nullable
private static final Method METHOD_THREAD_COUNT_FROM_THREAD_PER_TASK_EXECUTOR = getMethodForThreadCountFromThreadPerTaskExecutor();
private static final MethodHandle METHOD_HANDLE_THREAD_COUNT_FROM_THREAD_PER_TASK_EXECUTOR = getMethodHandleForThreadCountFromThreadPerTaskExecutor();

private static boolean allowIllegalReflectiveAccess = true;

Expand Down Expand Up @@ -461,20 +463,20 @@ private void monitorThreadPerTaskExecutor(MeterRegistry registry, ExecutorServic

private static long getThreadCountFromThreadPerTaskExecutor(ExecutorService executorService) {
try {
return (long) METHOD_THREAD_COUNT_FROM_THREAD_PER_TASK_EXECUTOR.invoke(executorService);
return (long) METHOD_HANDLE_THREAD_COUNT_FROM_THREAD_PER_TASK_EXECUTOR.invoke(executorService);
}
catch (Throwable e) {
throw new RuntimeException(e);
}
}

@Nullable
private static Method getMethodForThreadCountFromThreadPerTaskExecutor() {
private static MethodHandle getMethodHandleForThreadCountFromThreadPerTaskExecutor() {
try {
Class<?> clazz = Class.forName(CLASS_NAME_THREAD_PER_TASK_EXECUTOR);
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@juliojgd juliojgd Mar 13, 2025

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I think this could work

        Class<?> clazz = Class.forName(CLASS_NAME_THREAD_PER_TASK_EXECUTOR);
        // Get private access to the class
        MethodHandles.Lookup privateLookup = MethodHandles.privateLookupIn(clazz, MethodHandles.lookup());
        // Find the private method
        return privateLookup.findVirtual(clazz, "threadCount", MethodType.methodType(long.class));

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@juliojgd juliojgd Mar 13, 2025

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with methodhandles in theory the accesscheck occurs only once (during the lookup) but with plain reflection the access check occurs in every invocation. At least this is my understanding

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@izeye izeye Mar 13, 2025

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@juliojgd MethodHandles.privateLookupIn() requires JDK 9+, but Micrometer needs to work on JDK 8, so we can't call it directly.

Method method = clazz.getMethod("threadCount");
method.setAccessible(true);
return method;
return MethodHandles.lookup().unreflect(method);
}
catch (Throwable e) {
return null;
Expand Down