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Merged
mcculls merged 2 commits into from
Oct 13, 2025
Merged

Allow introspection of class-loader values #20

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6708fe3
Allow introspection of values computed by a ClassLoaderValue
mcculls Oct 12, 2025
fd822db
Allow removal of all values computed by a ClassLoaderValue
mcculls Oct 12, 2025
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33 changes: 31 additions & 2 deletions utils/src/main/java/datadog/instrument/utils/ClassLoaderValue.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.function.BiConsumer;

/**
* Lazily associate a computed value with (potentially) every {@link ClassLoader}. The computed
Expand Down Expand Up @@ -108,9 +109,37 @@ public final void remove(ClassLoader cl) {
}
}

/** Removes all values computed by this {@code ClassLoaderValue}. */
public final void clear() {
bootValue = null;
systemValue = null;
otherValues.clear();
}

/**
* Visits the values computed by this {@code ClassLoaderValue}, for diagnostic purposes.
*
* @param visitor the visitor of class-loader values
*/
public final void visit(BiConsumer<ClassLoader, V> visitor) {
if (bootValue != null) {
visitor.accept(BOOT_CLASS_LOADER, bootValue);
}
if (systemValue != null) {
visitor.accept(SYSTEM_CLASS_LOADER, systemValue);
}
for (Map.Entry<Object, V> entry : otherValues.entrySet()) {
// skip stale values by checking the associated class-loader
ClassLoader cl = ((ClassLoaderKey) entry.getKey()).get();
if (cl != null) {
visitor.accept(cl, entry.getValue());
}
}
}

/** For testing purposes. */
int size() {
return (null != bootValue ? 1 : 0) + (null != systemValue ? 1 : 0) + otherValues.size();
final int size() {
return (bootValue != null ? 1 : 0) + (systemValue != null ? 1 : 0) + otherValues.size();
}

/**
Expand Down
80 changes: 56 additions & 24 deletions utils/src/test/java/datadog/instrument/utils/ClassLoaderValueTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@
import static org.junit.jupiter.api.Assertions.assertEquals;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Timeout;
Expand Down Expand Up @@ -35,18 +37,18 @@ void basicOperation() {

assertThat(classLoaderValue.get(cl0)).isEqualTo("0=null");
assertThat(classLoaderValue.get(cl1)).matches("1=.*App.*");
assertThat(classLoaderValue.get(cl2)).matches("2=CL2");
assertThat(classLoaderValue.get(cl3)).matches("3=CL3");
assertThat(classLoaderValue.get(cl4)).matches("4=CL4");
assertThat(classLoaderValue.get(cl5)).matches("5=CL5");
assertThat(classLoaderValue.get(cl2)).isEqualTo("2=CL2");
assertThat(classLoaderValue.get(cl3)).isEqualTo("3=CL3");
assertThat(classLoaderValue.get(cl4)).isEqualTo("4=CL4");
assertThat(classLoaderValue.get(cl5)).isEqualTo("5=CL5");

assertEquals(6, classLoaderValue.size());

// repeated requests should return the same values
assertThat(classLoaderValue.get(cl5)).matches("5=CL5");
assertThat(classLoaderValue.get(cl4)).matches("4=CL4");
assertThat(classLoaderValue.get(cl3)).matches("3=CL3");
assertThat(classLoaderValue.get(cl2)).matches("2=CL2");
assertThat(classLoaderValue.get(cl5)).isEqualTo("5=CL5");
assertThat(classLoaderValue.get(cl4)).isEqualTo("4=CL4");
assertThat(classLoaderValue.get(cl3)).isEqualTo("3=CL3");
assertThat(classLoaderValue.get(cl2)).isEqualTo("2=CL2");
assertThat(classLoaderValue.get(cl1)).matches("1=.*App.*");
assertThat(classLoaderValue.get(cl0)).isEqualTo("0=null");

Expand All @@ -59,10 +61,10 @@ void basicOperation() {
// only the removed value should be replaced
assertThat(classLoaderValue.get(cl0)).isEqualTo("6=null");
assertThat(classLoaderValue.get(cl1)).matches("1=.*App.*");
assertThat(classLoaderValue.get(cl2)).matches("2=CL2");
assertThat(classLoaderValue.get(cl3)).matches("3=CL3");
assertThat(classLoaderValue.get(cl4)).matches("4=CL4");
assertThat(classLoaderValue.get(cl5)).matches("5=CL5");
assertThat(classLoaderValue.get(cl2)).isEqualTo("2=CL2");
assertThat(classLoaderValue.get(cl3)).isEqualTo("3=CL3");
assertThat(classLoaderValue.get(cl4)).isEqualTo("4=CL4");
assertThat(classLoaderValue.get(cl5)).isEqualTo("5=CL5");

assertEquals(6, classLoaderValue.size());

Expand All @@ -73,10 +75,10 @@ void basicOperation() {
// only the removed value should be replaced
assertThat(classLoaderValue.get(cl0)).isEqualTo("6=null");
assertThat(classLoaderValue.get(cl1)).matches("7=.*App.*");
assertThat(classLoaderValue.get(cl2)).matches("2=CL2");
assertThat(classLoaderValue.get(cl3)).matches("3=CL3");
assertThat(classLoaderValue.get(cl4)).matches("4=CL4");
assertThat(classLoaderValue.get(cl5)).matches("5=CL5");
assertThat(classLoaderValue.get(cl2)).isEqualTo("2=CL2");
assertThat(classLoaderValue.get(cl3)).isEqualTo("3=CL3");
assertThat(classLoaderValue.get(cl4)).isEqualTo("4=CL4");
assertThat(classLoaderValue.get(cl5)).isEqualTo("5=CL5");

assertEquals(6, classLoaderValue.size());

Expand All @@ -87,17 +89,23 @@ void basicOperation() {
// only the removed value should be replaced
assertThat(classLoaderValue.get(cl0)).isEqualTo("6=null");
assertThat(classLoaderValue.get(cl1)).matches("7=.*App.*");
assertThat(classLoaderValue.get(cl2)).matches("2=CL2");
assertThat(classLoaderValue.get(cl3)).matches("8=CL3");
assertThat(classLoaderValue.get(cl4)).matches("4=CL4");
assertThat(classLoaderValue.get(cl5)).matches("5=CL5");
assertThat(classLoaderValue.get(cl2)).isEqualTo("2=CL2");
assertThat(classLoaderValue.get(cl3)).isEqualTo("8=CL3");
assertThat(classLoaderValue.get(cl4)).isEqualTo("4=CL4");
assertThat(classLoaderValue.get(cl5)).isEqualTo("5=CL5");

assertEquals(6, classLoaderValue.size());

classLoaderValue.clear();

assertEquals(0, classLoaderValue.size());
}

@Test
@Timeout(30)
void removeStaleEntries() {
Map<ClassLoader, String> visited = new HashMap<>();

ClassLoader cl0 = null;
ClassLoader cl1 = ClassLoader.getSystemClassLoader();
ClassLoader cl2 = newCL("CL2");
Expand All @@ -107,15 +115,30 @@ void removeStaleEntries() {

assertEquals(0, classLoaderValue.size());

classLoaderValue.visit(visited::put);
assertEquals(0, visited.size());
visited.clear();

assertThat(classLoaderValue.get(cl0)).isEqualTo("0=null");
assertThat(classLoaderValue.get(cl1)).matches("1=.*App.*");
assertThat(classLoaderValue.get(cl2)).matches("2=CL2");
assertThat(classLoaderValue.get(cl3)).matches("3=CL3");
assertThat(classLoaderValue.get(cl4)).matches("4=CL4");
assertThat(classLoaderValue.get(cl5)).matches("5=CL5");
assertThat(classLoaderValue.get(cl2)).isEqualTo("2=CL2");
assertThat(classLoaderValue.get(cl3)).isEqualTo("3=CL3");
assertThat(classLoaderValue.get(cl4)).isEqualTo("4=CL4");
assertThat(classLoaderValue.get(cl5)).isEqualTo("5=CL5");

assertEquals(6, classLoaderValue.size());

classLoaderValue.visit(visited::put);
assertThat(visited.values())
.containsExactlyInAnyOrder(
classLoaderValue.get(cl0),
classLoaderValue.get(cl1),
classLoaderValue.get(cl2),
classLoaderValue.get(cl3),
classLoaderValue.get(cl4),
classLoaderValue.get(cl5));
visited.clear();

cl2 = null;
cl4 = null;

Expand All @@ -124,6 +147,15 @@ void removeStaleEntries() {
System.runFinalization();
ClassLoaderValue.removeStaleEntries();
}

classLoaderValue.visit(visited::put);
assertThat(visited.values())
.containsExactlyInAnyOrder(
classLoaderValue.get(cl0),
classLoaderValue.get(cl1),
classLoaderValue.get(cl3),
classLoaderValue.get(cl5));
visited.clear();
}

private static ClassLoader newCL(String name) {
Expand Down