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fix: OpenTelemetry transactions for failed requests keep their route name and otel context #5310

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Merged
jamescrosswell merged 2 commits into from
Jul 8, 2026
Merged

fix: OpenTelemetry transactions for failed requests keep their route name and otel context #5310

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2bac415
fix: OpenTelemetry transactions for failed requests keep their route …
jamescrosswell Jun 24, 2026
4b2eddb
Update src/Sentry/Internal/Hub.cs
jamescrosswell Jun 24, 2026
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13 changes: 11 additions & 2 deletions src/Sentry/Internal/Hub.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -667,8 +667,17 @@ private SentryId CaptureEvent(SentryEvent evt, SentryHint? hint, Scope scope)
{
// Event contains a terminal exception -> finish any current transaction as aborted
// Do this *after* the event was captured, so that the event is still linked to the transaction.
_options.LogDebug("Ending transaction as Aborted, due to unhandled exception.");
transaction.Finish(SpanStatus.Aborted);
// Skip for OpenTelemetry transactions - these get handled by the SpanProcessor instead. See https://github.com/getsentry/sentry-dotnet/pull/5310
if (transaction is IBaseTracer { IsOtelInstrumenter: true })

@Flash0ver Flash0ver Jul 7, 2026

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question: SpanProcessor vs OTLP Exporter

Does this only apply to Sentry.OpenTelemetry, and not to Sentry.OpenTelemetry.Exporter?
Doesn't the OTLP Exporter also set SentryOptions.Instrumenter to Instrumenter.OpenTelemetry?

Or am I confusing something here?

@Flash0ver Flash0ver Jul 7, 2026 •
edited
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oh ... wait ... I do misunderstand

Sentry.OpenTelemetry.Exporter doesn't start/finish Transactions/Spans, but "only" extracts/injects Sentry's Trace- and Baggage-Headers in order to propagate context ... due to also setting SentryOptions.DisableSentryTracing = true, and the NoOpTransaction class does not implement the IBaseTracer interface.

{
_options.LogDebug(
"Not ending OpenTelemetry transaction as Aborted; it is finished by the SentrySpanProcessor.");
}
else
{
Comment on lines +673 to +677

@sentry sentry Bot Jun 24, 2026

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Bug: If SentrySpanProcessor.OnEnd is not called after an exception, the associated OTel transaction will never be finished or sent, leading to lost data.
Severity: MEDIUM

Suggested Fix

Implement a fallback mechanism, such as a timeout, to ensure transactions are eventually finished and reported even if SentrySpanProcessor.OnEnd is not called. Consider adding documentation about the implicit dependency on the OnEnd event firing.

Prompt for AI Agent 
Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: src/Sentry/Internal/Hub.cs#L673-L677

Potential issue: The code change skips finishing OpenTelemetry-instrumented transactions
during unhandled exceptions, instead relying on `SentrySpanProcessor.OnEnd` to complete
them. However, the `OnEnd` event is not guaranteed to fire in all scenarios, especially
in non-ASP.NET Core contexts or with certain framework-level exceptions. If `OnEnd` is
not called, the transaction will never be finished or sent to Sentry, remaining in
memory until garbage collected. This leads to the silent loss of performance data for
failed requests without any fallback mechanism.

Did we get this right? 👍 / 👎 to inform future reviews.

@jamescrosswell jamescrosswell Jun 24, 2026

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OnEnd is already the only path that finishes OTel transactions — every successful request relies on it, not just failed ones, so this doesn't add a new dependency. The cases where it wouldn't fire are (1) the Activity being sampled out, where we deliberately don't send a transaction, and (2) a process-terminating crash, where the flush is unreliable regardless and the only thing we'd have sent is the malformed transaction this PR removes.

For the ASP.NET Core path in the issue, the host always stops the activity, so OnEnd runs. A timeout fallback would just resurrect the early-finish bug.

_options.LogDebug("Ending transaction as Aborted, due to unhandled exception.");
transaction.Finish(SpanStatus.Aborted);
}
}

return id;
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30 changes: 30 additions & 0 deletions test/Sentry.Tests/HubTests.cs
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Expand Up @@ -545,6 +545,36 @@ public void CaptureEvent_TerminalUnhandledException_AbortsActiveTransaction()
transaction.IsFinished.Should().BeTrue();
}

[Fact]
public void CaptureEvent_TerminalUnhandledException_DoesNotAbortOpenTelemetryTransaction()
{
// OpenTelemetry-instrumented transactions are owned and finished by the SentrySpanProcessor
// when the underlying Activity ends (which is also where the transaction name, operation and
// otel/response contexts get populated). Finishing them early here would capture them with the
// raw activity name and no otel context. See https://github.com/getsentry/sentry-dotnet/issues/5091

// Arrange
_fixture.Options.TracesSampleRate = 1.0;
_fixture.Options.Instrumenter = Instrumenter.OpenTelemetry;
var hub = _fixture.GetSut();

var transactionContext = new TransactionContext("test", "operation")
{
Instrumenter = Instrumenter.OpenTelemetry
};
var transaction = hub.StartTransaction(transactionContext);
hub.ConfigureScope(scope => scope.Transaction = transaction);

var exception = new Exception("test");
exception.SetSentryMechanism("test", handled: false, terminal: true);

// Act
hub.CaptureEvent(new SentryEvent(exception));

// Assert
transaction.IsFinished.Should().BeFalse();
}

[Fact]
public void CaptureEvent_NonTerminalUnhandledException_DoesNotAbortActiveTransaction()
{
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