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Fix Exception Replay in Lambda #8849

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nhulston wants to merge 6 commits into from
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Fix Exception Replay in Lambda #8849

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c4a17c6
add fallback for lambda
nhulston May 19, 2025
a60af39
unit test
nhulston May 19, 2025
03689f9
mock exception to return truncated stack like Lambda
nhulston May 20, 2025
130556a
Merge branch 'master' into nicholas.hulston/fix-exception-replay-in-l…
nhulston May 20, 2025
a968384
Merge branch 'master' into nicholas.hulston/fix-exception-replay-in-l…
nhulston May 20, 2025
1f12c25
Merge branch 'master' into nicholas.hulston/fix-exception-replay-in-l…
nhulston May 21, 2025
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unit test
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@nhulston
nhulston committed May 19, 2025
commit a60af39e5967d8bd23c3be8ce4e1a0e0ee4a8589
33 changes: 33 additions & 0 deletions ...t-debugger/src/test/java/com/datadog/debugger/exception/DefaultExceptionDebuggerTest.java
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Expand Up @@ -280,6 +280,39 @@ public void filteringOutErrors() {
verify(manager, times(0)).isAlreadyInstrumented(any());
}

@Test
public void lambdaTruncatedInnerTraceFallback() {
RuntimeException exception = new RuntimeException("lambda");
String fingerprint = Fingerprinter.fingerprint(exception, classNameFiltering);
AgentSpan span = mock(AgentSpan.class);
doAnswer(this::recordTags).when(span).setTag(anyString(), anyString());
when(span.getTag(anyString())).thenAnswer(inv -> spanTags.get(inv.getArgument(0)));
when(span.getTags()).thenReturn(spanTags);

exceptionDebugger.handleException(exception, span);
assertWithTimeout(
() -> exceptionDebugger.getExceptionProbeManager().isAlreadyInstrumented(fingerprint),
Duration.ofSeconds(30));

generateSnapshots(exception);

ExceptionProbeManager.ThrowableState state =
exceptionDebugger.getExceptionProbeManager().getStateByThrowable(exception);
List<Snapshot> snapshots = state.getSnapshots();
StackTraceElement ste = exception.getStackTrace()[0];
CapturedStackFrame dummyFrame = CapturedStackFrame.from(ste);
for (Snapshot snap : snapshots) {
snap.getStack().add(0, dummyFrame);
}
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@jpbempel jpbempel May 20, 2025

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Can we mock instead the exception that is provided to handleException instead to return a truncated stack like what it is done by AWS lambda?

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@nhulston nhulston May 20, 2025

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LMK what you think -- i ended up having to mock the snapshot, probe, exception state, and exception probe manager

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@jpbempel jpbempel May 20, 2025 •
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i ended up having to mock the snapshot, probe, exception state, and exception probe manager

I am not sure it is necessary to do all of that, collecting real exception in snapshot is what happen anyway.
What matters is the truncated stacktrace for main exception


// This should hit the `currentIdx < 0` branch and fallback to i=0
exceptionDebugger.handleException(exception, span);

String tagName = String.format(SNAPSHOT_ID_TAG_FMT, 0);
assertTrue(spanTags.containsKey(tagName));
assertEquals(snapshots.get(0).getId(), spanTags.get(tagName));
}

private Object recordTags(InvocationOnMock invocationOnMock) {
Object[] args = invocationOnMock.getArguments();
String key = (String) args[0];
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