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Notify listeners when the scope top changes after switching scope stacks #8797

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Merged
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May 12, 2025
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Notify listeners when the scope top changes after switching scope stacks #8797

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6 changes: 6 additions & 0 deletions dd-trace-core/src/main/java/datadog/trace/core/scopemanager/ContinuableScopeManager.java
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Original file line number Diff line number Diff line change
Expand Up @@ -384,7 +384,13 @@ private class ContinuableScopeState implements ScopeState {

@Override
public void activate() {
ContinuableScope oldScope = tlsScopeStack.get().top;
tlsScopeStack.set(localScopeStack);
ContinuableScope newScope = localScopeStack.top;
if (oldScope != newScope && newScope != null) {
newScope.beforeActivated();
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we call before and after on a row without doing anything in between. Can this be simplified ?

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@mcculls mcculls May 12, 2025 •
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There's a very subtle difference - beforeActivated calls the profiling integration, while afterActivated calls the registered listeners.

In one place in the code beforeActivated is called before changing the top value:

dd-trace-java/dd-trace-core/src/main/java/datadog/trace/core/scopemanager/ScopeStack.java

Lines 69 to 76 in e8a2156

scope.beforeActivated();
if (top != null) {
stack.push(top);
} else {
onBecomeNonEmpty();
}
top = scope;
scope.afterActivated();

but in another part of the code, they are called at the same time after the top has changed:

dd-trace-java/dd-trace-core/src/main/java/datadog/trace/core/scopemanager/ScopeStack.java

Lines 58 to 59 in e8a2156

curScope.beforeActivated();
curScope.afterActivated();

In terms of actual implementation the profiling integration is just clearing some caches, so there is flexibility here and this could all be done in one method as long as the profiling integration is always called first.

However since the profiling integration will need to be refactored to make it context-first, that's something I will do in a separate PR.

newScope.afterActivated();
}
}

@Override
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