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Fix SimpleExemplarReservoir for cumulative #5230

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merged 13 commits into from
Jan 18, 2024
Merged

Fix SimpleExemplarReservoir for cumulative #5230

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Fix SimpleExemplarReservoir for cumulative
cijothomas Jan 17, 2024
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changelog
cijothomas Jan 17, 2024
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Merge branch 'main' into cijothomas/exemplar-reset
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fix pr
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cijothomas Jan 18, 2024
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Update test/OpenTelemetry.Tests/Metrics/MetricExemplarTests.cs
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Merge branch 'main' into cijothomas/exemplar-reset
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4 changes: 4 additions & 0 deletions src/OpenTelemetry/CHANGELOG.md
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Expand Up @@ -15,6 +15,10 @@
state compared to the current activity. For details see:
[#5136](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5136)

* Fixed an issue where `SimpleExemplarReservoir` was not resetting internal
state for cumulative temporality.
[#5230](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5230)

## 1.7.0

Released 2023-Dec-08
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8 changes: 6 additions & 2 deletions src/OpenTelemetry/Metrics/Exemplar/SimpleExemplarReservoir.cs
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Expand Up @@ -57,9 +57,13 @@ public override Exemplar[] Collect(ReadOnlyTagCollection actualTags, bool reset)
if (reset)
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unrelated but kind of related nit: maybe this variable should be named isDelta for readability?

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yes... The Reservoir itself is not necessarily aware of temporality concept. All it needs to know is if it should reset its internal state or not.. The caller knows temporality and passes reset to this...

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Not a blocker for this PR, but just looking at this API shape, is the correct thing to do to expose bool reset?

SDKs are free to decide whether "collect" should also reset internal storage for delta temporal aggregation collection, or use a more optimal implementation.

Curious what other languages have done to solve this.

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The current APIs need to be revised before exposing them to public (its marked internal), and there are many TODOs to be solved.

{
this.runningExemplars[i].Timestamp = default;
this.measurementsSeen = 0;
}
}
}

// Reset internal state irrespective of temporality.
// This ensures incoming measurements have fair chance
// of making it to the reservoir.
this.measurementsSeen = 0;
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return this.tempExemplars;
}
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14 changes: 11 additions & 3 deletions test/OpenTelemetry.Tests/Metrics/MetricExemplarTests.cs
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Expand Up @@ -19,8 +19,10 @@ public MetricExemplarTests(ITestOutputHelper output)
this.output = output;
}

[Fact]
public void TestExemplarsCounter()
[Theory]
[InlineData(MetricReaderTemporalityPreference.Cumulative)]
[InlineData(MetricReaderTemporalityPreference.Delta)]
public void TestExemplarsCounter(MetricReaderTemporalityPreference temporality)
{
DateTime testStartTime = DateTime.UtcNow;
var exportedItems = new List<Metric>();
Expand All @@ -33,7 +35,7 @@ public void TestExemplarsCounter()
.SetExemplarFilter(new AlwaysOnExemplarFilter())
.AddInMemoryExporter(exportedItems, metricReaderOptions =>
{
metricReaderOptions.TemporalityPreference = MetricReaderTemporalityPreference.Delta;
metricReaderOptions.TemporalityPreference = temporality;
}));

var measurementValues = GenerateRandomValues(10);
Expand All @@ -48,6 +50,12 @@ public void TestExemplarsCounter()
Assert.True(metricPoint.Value.StartTime >= testStartTime);
Assert.True(metricPoint.Value.EndTime != default);
var exemplars = GetExemplars(metricPoint.Value);

// TODO: Modify the test to better test cumulative.
// In cumulative where SimpleExemplarReservoir's size is
// more than the count of new measurements, it is possible
// that the exemplar value is for a measurement that was recorded in the prior
// cycle. The current ValidateExemplars() does not handle this case.
ValidateExemplars(exemplars, metricPoint.Value.StartTime, metricPoint.Value.EndTime, measurementValues, false);

exportedItems.Clear();
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