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fix: don't label upstream-unsampled transactions as backpressure #5841

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Merged
jamescrosswell merged 2 commits into from
Nov 1, 2026
Merged

fix: don't label upstream-unsampled transactions as backpressure #5841

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cdc34cc
fix: don't label upstream-unsampled transactions as backpressure
chiliec Oct 30, 2026
77eb37e
test: fold upstream-unsampled cases into backpressure theory
chiliec Oct 31, 2026
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2 changes: 1 addition & 1 deletion src/Sentry/Internal/Hub.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -245,7 +245,7 @@ internal ITransactionTracer StartTransaction(
{
// If sampling out is only a result of the downsampling then we specify the reason as backpressure
// management... otherwise the event would have been sampled out anyway, so it's just regular sampling.
discardReason = sampleRand < optionsSampleRate ? DiscardReason.Backpressure : DiscardReason.SampleRate;
discardReason = context.IsSampled is null && sampleRand < optionsSampleRate ? DiscardReason.Backpressure : DiscardReason.SampleRate;
}

if (context.IsSampled is null && _options.TracesSampleRate is not null)
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14 changes: 8 additions & 6 deletions test/Sentry.Tests/HubTests.cs
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Expand Up @@ -1033,14 +1033,16 @@ public void StartTransaction_Backpressure_Downsamples(bool usesTracesSampler)
}

[Theory]
[InlineData(true, 0.4f, "backpressure")]
[InlineData(true, 0.6f, "sample_rate")]
[InlineData(false, 0.4f, "backpressure")]
[InlineData(false, 0.6f, "sample_rate")]
public void StartTransaction_Backpressure_SetsDiscardReason(bool usesTracesSampler, double sampleRand, string discardReason)
[InlineData(true, null, 0.4f, "backpressure")]
[InlineData(true, null, 0.6f, "sample_rate")]
[InlineData(false, null, 0.4f, "backpressure")]
[InlineData(false, null, 0.6f, "sample_rate")]
[InlineData(true, false, 0.4f, "backpressure")]
[InlineData(false, false, 0.4f, "sample_rate")]
public void StartTransaction_Backpressure_SetsDiscardReason(bool usesTracesSampler, bool? isSampledUpstream, double sampleRand, string discardReason)
{
// Arrange
var transactionContext = new TransactionContext("name", "operation");
var transactionContext = new TransactionContext("name", "operation", isSampled: isSampledUpstream);

var clock = new MockClock(DateTimeOffset.UtcNow);
_fixture.SampleRandHelper = Substitute.For<ISampleRandHelper>();
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