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Add capping on SourceFile tracking queue #9245

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Merged
merged 1 commit into from
Jul 25, 2025
Merged

Add capping on SourceFile tracking queue #9245

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4 changes: 3 additions & 1 deletion dd-java-agent/agent-debugger/src/main/java/com/datadog/debugger/agent/DebuggerAgent.java
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Original file line number Diff line number Diff line change
Expand Up @@ -478,7 +478,9 @@ private static void addReportToFlare(ZipOutputStream zip) throws IOException {
"SymbolDB stats:",
symbolDBStats,
"Exception Fingerprints:",
exceptionFingerprints);
exceptionFingerprints,
"SourceFile tracking entries:",
String.valueOf(classesToRetransformFinder.getClassNamesBySourceFile().size()));
TracerFlare.addText(zip, "dynamic_instrumentation.txt", content);
}
}
25 changes: 23 additions & 2 deletions ...gent-debugger/src/main/java/com/datadog/debugger/agent/SourceFileTrackingTransformer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
import com.datadog.debugger.util.ClassFileHelper;
import com.datadog.debugger.util.ClassNameFiltering;
import datadog.trace.api.Config;
import datadog.trace.relocate.api.RatelimitedLogger;
import datadog.trace.util.AgentTaskScheduler;
import datadog.trace.util.Strings;
import java.lang.instrument.ClassFileTransformer;
Expand All @@ -14,6 +15,7 @@
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

Expand All @@ -24,10 +26,15 @@
*/
public class SourceFileTrackingTransformer implements ClassFileTransformer {
private static final Logger LOGGER = LoggerFactory.getLogger(SourceFileTrackingTransformer.class);
private static final int MINUTES_BETWEEN_ERROR_LOG = 5;
static final int MAX_QUEUE_SIZE = 4096;

private final RatelimitedLogger ratelimitedLogger =
new RatelimitedLogger(LOGGER, MINUTES_BETWEEN_ERROR_LOG, TimeUnit.MINUTES);
private final ClassesToRetransformFinder finder;
private final Queue<SourceFileItem> queue = new ConcurrentLinkedQueue<>();
private final AgentTaskScheduler scheduler = AgentTaskScheduler.INSTANCE;
private final AtomicInteger queueSize = new AtomicInteger(0);
private AgentTaskScheduler.Scheduled<Runnable> scheduled;
// this field MUST only be used in flush() calling thread
private ClassNameFiltering classNameFilter;
Expand Down Expand Up @@ -55,14 +62,23 @@ void flush() {
if (queue.isEmpty()) {
return;
}
int size = queue.size();
int itemCount = 0;
long start = System.nanoTime();
SourceFileItem item;
while ((item = queue.poll()) != null) {
queueSize.decrementAndGet();
registerSourceFile(item.className, item.classfileBuffer);
itemCount++;
}
LOGGER.debug(
"flushing {} source file items in {}ms", size, (System.nanoTime() - start) / 1_000_000);
"flushing {} source file items in {}ms, totalentries: {}",
itemCount,
(System.nanoTime() - start) / 1_000_000,
finder.getClassNamesBySourceFile().size());
}

int getQueueSize() {
return queueSize.get();
}

@Override
Expand All @@ -76,7 +92,12 @@ public byte[] transform(
if (className == null) {
return null;
}
if (queueSize.get() >= MAX_QUEUE_SIZE) {
ratelimitedLogger.warn("SourceFile Tracking queue full, dropping class: {}", className);
return null;
}
queue.add(new SourceFileItem(className, classfileBuffer));
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probably no real concerns of a race condition here given where this lives but thought I'd call it out.

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yeah multiple class loads can happen concurrently here, we can overshoot the limit but this is not a problem. What we want here is putting a limitation of the total item that are queued to not fill up the memory. 4096 is arbitrary.

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that's what I thought but wanted to double check.

queueSize.incrementAndGet();
return null;
}

Expand Down
17 changes: 17 additions & 0 deletions ...-debugger/src/test/java/com/datadog/debugger/agent/SourceFileTrackingTransformerTest.java
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@@ -1,5 +1,6 @@
package com.datadog.debugger.agent;

import static com.datadog.debugger.agent.SourceFileTrackingTransformer.MAX_QUEUE_SIZE;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static utils.TestClassFileHelper.getClassFileBytes;

Expand Down Expand Up @@ -138,6 +139,22 @@ void thirdPartyExcludes() throws IllegalClassFormatException {
assertEquals(0, finder.getClassNamesBySourceFile().size());
}

@Test
void maxQueue() throws IllegalClassFormatException {
ClassesToRetransformFinder finder = new ClassesToRetransformFinder();
SourceFileTrackingTransformer sourceFileTrackingTransformer =
new SourceFileTrackingTransformer(finder);
for (int i = 0; i < MAX_QUEUE_SIZE + 10; i++) {
sourceFileTrackingTransformer.transform(
null,
getInternalName(TopLevelHelper.class),
null,
null,
getClassFileBytes(TopLevelHelper.class));
}
assertEquals(MAX_QUEUE_SIZE, sourceFileTrackingTransformer.getQueueSize());
}

private static void replaceInByteArray(byte[] buffer, byte[] oldBytes, byte[] newBytes) {
int oldIdx = 0;
for (int i = 0; i < buffer.length; i++) {
Expand Down
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