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feat(tracer): Update the TagsList infrastructure to allow a secondary OtelName #8971

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feat(tracer): Update the TagsList infrastructure to allow a secondary OtelName #8971

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59cd901
feat(tracer): Update the TagsListGenerator to support a TagName (DD s…
zacharycmontoya Jul 28, 2026
0403a47
Update all generated tags objects without using the new OTelName feature
zacharycmontoya Jul 28, 2026
5ab6bed
Apply the OTelName to all HttpStatusCode tags, re-generate the tags, …
zacharycmontoya Jul 28, 2026
4aa8d2a
Fix casing from OTel to Otel
zacharycmontoya Jul 29, 2026
77b5fec
Fix issues from automated code review:
zacharycmontoya Jul 29, 2026
4d9676d
Fix issues from automated code review:
zacharycmontoya Jul 29, 2026
471f234
Fixup rename to Otel
zacharycmontoya Jul 29, 2026
0067259
Fixup removal of serializers having the otel semantics state
zacharycmontoya Jul 29, 2026
807e7ff
Add code comment for trace filter
zacharycmontoya Jul 29, 2026
2a29f8b
Fix CI failures from HTTP status code tag refactor
zacharycmontoya Jul 31, 2026
9712b4a
Fix Windows CI failure in TagsListGenerator OTel alias code path
zacharycmontoya Jul 31, 2026
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145 changes: 135 additions & 10 deletions tracer/src/Datadog.Trace.SourceGenerators/TagsListGenerator/Sources.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,11 @@ public TagAttribute(string tagName) =>
/// Gets the name of the datadog tag the property corresponds to

@andrewlock andrewlock Aug 3, 2026

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In the case where a tag is only used by Otel, we'd still set TagName. I'm wondering if it will confuse anyone 🤔 Maybe we could/should call it out explicitly in doc comments for TagName? WDYT?

/// </summary>
public string TagName { get; }

/// <summary>
/// Gets or sets the OpenTelemetry semantic convention name that aliases <see cref=""TagName""/>.
/// </summary>
public string? OtelName { get; set; }
}

/// <summary>
Expand Down Expand Up @@ -118,6 +123,27 @@ partial class ")
.Append(@"Bytes => [")
.Append(tagByteArray)
.AppendLine(@"];");

if (property.OtelTagValue is not null)
{
var oTelTagByteArray = string.Join(", ", MessagePackHelper.GetValueInRawMessagePackIEnumerable(property.OtelTagValue));

sb.Append(
@"
// ")
.Append(property.PropertyName)
.Append(@"OtelBytes = MessagePack.Serialize(""")
.Append(property.OtelTagValue)
.Append(@""");");

sb.Append(
@"
private static ReadOnlySpan<byte> ")
.Append(property.PropertyName)
.Append(@"OtelBytes => [")
.Append(oTelTagByteArray)
.AppendLine(@"];");
}
}

sb.Append(
Expand Down Expand Up @@ -148,6 +174,27 @@ partial class ")
sb.Append(
@",
");

if (property.OtelTagValue is not null)
{
sb.Append('"')
.Append(property.OtelTagValue)
.Append(@""" => ")
.Append(property.PropertyName);

switch (property.PropertyType)
{
case TagListGenerator.PropertyType.NullableInt:
sb.Append(" is null ? null : Datadog.Trace.Util.IntStringCache.ToInvariantString(")
.Append(property.PropertyName)
.Append(".Value)");
break;
}

sb.Append(
@",
");
}
}

sb.Append(
Expand All @@ -169,11 +216,26 @@ public override void SetTag(string key, string? value)
continue;
}

sb.Append(@"case """)
.Append(property.TagValue)
.Append(
@""":
if (property.OtelTagValue is not null)
{
sb.Append(@"case """)
.Append(property.TagValue)
.Append(@""":")
.Append(@"
case """)
.Append(property.OtelTagValue)
.Append(
@""":
");
}
else
{
sb.Append(@"case """)
.Append(property.TagValue)
.Append(
@""":
");
}

if (property.PropertyType is TagListGenerator.PropertyType.NullableInt)
{
Expand Down Expand Up @@ -223,6 +285,15 @@ public override void SetTag(string key, string? value)
.Append(
@""":
");

if (property.OtelTagValue is not null)
{
sb.Append(@"case """)
.Append(property.OtelTagValue)
.Append(
@""":
");
}
}
}

Expand All @@ -244,7 +315,7 @@ public override void SetTag(string key, string? value)
}
}

public override void EnumerateTags<TProcessor>(ref TProcessor processor)
public override void EnumerateTags<TProcessor>(ref TProcessor processor, bool openTelemetrySemanticsEnabled)
{
");
foreach (var property in tagList.TagProperties)
Expand All @@ -256,13 +327,40 @@ public override void EnumerateTags<TProcessor>(ref TProcessor processor)
.Append(property.PropertyName)
.Append(@" is not null)
{
processor.Process(new TagItem<int>(""")
");

if (property.OtelTagValue is not null)
{
sb.Append(@"if (openTelemetrySemanticsEnabled)
{
processor.Process(new TagItem<int>(""")
.Append(property.OtelTagValue)
.Append(@""", ")
.Append(property.PropertyName)
.Append(@".Value, ")
.Append(property.PropertyName)
.Append(@"OtelBytes));
}
else
{
");
}

sb.Append(@"processor.Process(new TagItem<int>(""")
.Append(property.TagValue)
.Append(@""", ")
.Append(property.PropertyName)
.Append(@".Value, ")
.Append(property.PropertyName)
.Append(@"Bytes));
.Append(@"Bytes));");

if (property.OtelTagValue is not null)
{
sb.Append(@"
}");
}

sb.Append(@"
}

");
Expand All @@ -272,13 +370,40 @@ public override void EnumerateTags<TProcessor>(ref TProcessor processor)
.Append(property.PropertyName)
.Append(@" is not null)
{
processor.Process(new TagItem<string>(""")
");

if (property.OtelTagValue is not null)
{
sb.Append(@"if (openTelemetrySemanticsEnabled)
{
processor.Process(new TagItem<string>(""")
.Append(property.OtelTagValue)
.Append(@""", ")
.Append(property.PropertyName)
.Append(@", ")
.Append(property.PropertyName)
.Append(@"OtelBytes));
}
else
{
");
}

sb.Append(@"processor.Process(new TagItem<string>(""")
.Append(property.TagValue)
.Append(@""", ")
.Append(property.PropertyName)
.Append(@", ")
.Append(property.PropertyName)
.Append(@"Bytes));
.Append(@"Bytes));");

if (property.OtelTagValue is not null)
{
sb.Append(@"
}");
}

sb.Append(@"
}

");
Expand All @@ -287,7 +412,7 @@ public override void EnumerateTags<TProcessor>(ref TProcessor processor)
}

sb.Append(
@"base.EnumerateTags(ref processor);
@"base.EnumerateTags(ref processor, openTelemetrySemanticsEnabled);
}

protected override void WriteAdditionalTags(System.Text.StringBuilder sb)
Expand Down
48 changes: 47 additions & 1 deletion tracer/src/Datadog.Trace.SourceGenerators/TagsListGenerator/TagListGenerator.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -139,6 +139,7 @@ private static IEnumerable<TagList> GetTagLists(ImmutableArray<PropertyTag> tagP
List<DiagnosticInfo>? diagnostics = null;
bool hasMisconfiguredInput = false;
string? key = null;
string? otelKey = null;

foreach (AttributeData attributeData in propertySymbol!.GetAttributes())
{
Expand Down Expand Up @@ -191,6 +192,48 @@ private static IEnumerable<TagList> GetTagLists(ImmutableArray<PropertyTag> tagP
hasMisconfiguredInput = true;
break;
}

if (isTag)
{
foreach (var namedArgument in attributeData.NamedArguments)
{
if (namedArgument.Key != "OtelName")
{
continue;
}

if (namedArgument.Value.Kind == TypedConstantKind.Error)
{
hasMisconfiguredInput = true;
break;
}

otelKey = (string?)namedArgument.Value.Value;
if (string.IsNullOrEmpty(otelKey))
{
diagnostics ??= new List<DiagnosticInfo>();
diagnostics.Add(InvalidKeyDiagnostic.CreateInfo(attributeData.ApplicationSyntaxReference?.GetSyntax()));
hasMisconfiguredInput = true;
break;
}

if (otelKey == "_dd.origin")
{
diagnostics ??= new List<DiagnosticInfo>();
diagnostics.Add(InvalidUseOfOriginDiagnostic.CreateInfo(attributeData.ApplicationSyntaxReference?.GetSyntax()));
hasMisconfiguredInput = true;
break;
}

if (otelKey == "language")
{
diagnostics ??= new List<DiagnosticInfo>();
diagnostics.Add(InvalidUseOfLanguageDiagnostic.CreateInfo(attributeData.ApplicationSyntaxReference?.GetSyntax()));
hasMisconfiguredInput = true;
break;
}
}
}
}
}

Expand Down Expand Up @@ -242,6 +285,7 @@ private static IEnumerable<TagList> GetTagLists(ImmutableArray<PropertyTag> tagP
isReadOnly: propertySymbol!.IsReadOnly,
propertyName: propertySymbol.Name,
tagValue: key!,
otelTagValue: otelKey,
isTag: isTag,
propertyType: propertyType);

Expand Down Expand Up @@ -304,14 +348,16 @@ internal readonly record struct PropertyTag
public readonly bool IsReadOnly;
public readonly string PropertyName;
public readonly string TagValue;
public readonly string? OtelTagValue;
public readonly bool IsTag;
public readonly PropertyType PropertyType;

public PropertyTag(string nameSpace, string className, bool isReadOnly, string propertyName, string tagValue, bool isTag, PropertyType propertyType)
public PropertyTag(string nameSpace, string className, bool isReadOnly, string propertyName, string tagValue, string? otelTagValue, bool isTag, PropertyType propertyType)
{
IsReadOnly = isReadOnly;
PropertyName = propertyName;
TagValue = tagValue;
OtelTagValue = otelTagValue;
IsTag = isTag;
Namespace = nameSpace;
ClassName = className;
Expand Down
12 changes: 6 additions & 6 deletions tracer/src/Datadog.Trace/Agent/AgentWriter.cs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -69,7 +69,7 @@ internal sealed class AgentWriter : IAgentWriter
private bool _traceMetricsEnabled;

public AgentWriter(IApi api, IStatsAggregator? statsAggregator, IStatsdManager statsd, TracerSettings settings)
: this(api, statsAggregator, statsd, maxBufferSize: settings.TraceBufferSize, batchInterval: settings.TraceBatchInterval, apmTracingEnabled: settings.ApmTracingEnabled, initialTracerMetricsEnabled: settings.Manager.InitialMutableSettings.TracerMetricsEnabled, openTelemetrySemanticsEnabled: settings.OtelSemanticsEnabled)
: this(api, statsAggregator, statsd, maxBufferSize: settings.TraceBufferSize, batchInterval: settings.TraceBatchInterval, apmTracingEnabled: settings.ApmTracingEnabled, initialTracerMetricsEnabled: settings.Manager.InitialMutableSettings.TracerMetricsEnabled)
{
settings.Manager.SubscribeToChanges(changes =>
{
Expand All @@ -82,12 +82,12 @@ public AgentWriter(IApi api, IStatsAggregator? statsAggregator, IStatsdManager s
});
}

public AgentWriter(IApi api, IStatsAggregator? statsAggregator, IStatsdManager statsd, bool automaticFlush = true, int maxBufferSize = 1024 * 1024 * 10, int batchInterval = 100, bool apmTracingEnabled = true, bool initialTracerMetricsEnabled = false, bool openTelemetrySemanticsEnabled = false)
: this(api, statsAggregator, statsd, MovingAverageKeepRateCalculator.CreateDefaultKeepRateCalculator(), automaticFlush, maxBufferSize, batchInterval, apmTracingEnabled, initialTracerMetricsEnabled, openTelemetrySemanticsEnabled)
public AgentWriter(IApi api, IStatsAggregator? statsAggregator, IStatsdManager statsd, bool automaticFlush = true, int maxBufferSize = 1024 * 1024 * 10, int batchInterval = 100, bool apmTracingEnabled = true, bool initialTracerMetricsEnabled = false)
: this(api, statsAggregator, statsd, MovingAverageKeepRateCalculator.CreateDefaultKeepRateCalculator(), automaticFlush, maxBufferSize, batchInterval, apmTracingEnabled, initialTracerMetricsEnabled)
{
}

internal AgentWriter(IApi api, IStatsAggregator? statsAggregator, IStatsdManager statsd, IKeepRateCalculator traceKeepRateCalculator, bool automaticFlush, int maxBufferSize, int batchInterval, bool apmTracingEnabled, bool initialTracerMetricsEnabled, bool openTelemetrySemanticsEnabled)
internal AgentWriter(IApi api, IStatsAggregator? statsAggregator, IStatsdManager statsd, IKeepRateCalculator traceKeepRateCalculator, bool automaticFlush, int maxBufferSize, int batchInterval, bool apmTracingEnabled, bool initialTracerMetricsEnabled)
{
_statsAggregator = statsAggregator ?? new NullStatsAggregator();

Expand All @@ -98,8 +98,8 @@ internal AgentWriter(IApi api, IStatsAggregator? statsAggregator, IStatsdManager

ISpanBufferSerializer CreateSpanSerializer() => api.TracesEncoding switch
{
TracesEncoding.OtlpJson => new OtlpTracesJsonSerializer(openTelemetrySemanticsEnabled),
TracesEncoding.OtlpProtobuf => new OtlpTracesProtobufSerializer(openTelemetrySemanticsEnabled),
TracesEncoding.OtlpJson => new OtlpTracesJsonSerializer(),
TracesEncoding.OtlpProtobuf => new OtlpTracesProtobufSerializer(),
_ => new SpanBufferMessagePackSerializer(SpanFormatterResolver.Instance),
};

Expand Down
2 changes: 1 addition & 1 deletion tracer/src/Datadog.Trace/Agent/MessagePack/SpanMessagePackFormatter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -510,7 +510,7 @@ private int WriteTags(ref byte[] bytes, int offset, in SpanModel model, ITagProc

// Write span tags
var tagWriter = new TagWriter(this, tagProcessors, bytes, offset);
span.Tags.EnumerateTags(ref tagWriter);
span.Tags.EnumerateTags(ref tagWriter, span.OpenTelemetrySemanticsEnabled);
bytes = tagWriter.Bytes;
offset = tagWriter.Offset;
count += tagWriter.Count;
Expand Down
7 changes: 6 additions & 1 deletion tracer/src/Datadog.Trace/Agent/TraceSamplers/TraceFilter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,10 @@ static void BuildFilterTags(List<string>? filters, out List<string> keyFilters,
/// <summary>
/// Returns true if the trace should be kept, false if it should be rejected.
/// Evaluation is based on the root span only.
/// Note: When a tag has both a DD and OTel name and is strongly typed in our ITags implementations,
/// there are two diverging behaviors:
/// - When applying a filter tag, the search checks both DD and OTel tag keys (and the singular tag value)
/// - When applying a filter tag regex, the search only checks one tag key (DD or Otel) based on the span's configured semantics setting.

@andrewlock andrewlock Aug 3, 2026

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We could tweak that, so that it applies to both cases, at the expense of an additional enumeration for every span, regardless of the setting. Given the performance impact for everyone, and the generally low usage, I think the current approach makes total sense, even though it is potentially a bit confusing.

/// </summary>
public bool ShouldKeepTrace(Span rootSpan)
{
Expand All @@ -95,6 +99,7 @@ public bool ShouldKeepTrace(Span rootSpan)
}

// 2a. Reject filtering: reject if any tag matches reject filters
// With DD vs OTel semantics: Simple tag names check both key names and the (singular) value.
foreach (var filter in _filterTagKeysReject)
{
// Key-only filter: matches if tag key exists with any value
Expand Down Expand Up @@ -159,7 +164,7 @@ public bool ShouldKeepTrace(Span rootSpan)
private static bool MatchesRegexTagFilter(Span span, RegexTagFilter filter)
{
var processor = new RegexTagFilterProcessor(filter);
span.Tags.EnumerateTags(ref processor);
span.Tags.EnumerateTags(ref processor, span.OpenTelemetrySemanticsEnabled);
return processor.Matched;
}

Expand Down
2 changes: 1 addition & 1 deletion tracer/src/Datadog.Trace/Ci/Agent/MessagePack/SpanMessagePackFormatter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -220,7 +220,7 @@ private int WriteTags(ref byte[] bytes, int offset, Span span, ITags tags, ITagP

// Write span tags
var tagWriter = new TagWriter(this, tagProcessors, bytes, offset);
tags.EnumerateTags(ref tagWriter);
tags.EnumerateTags(ref tagWriter, span.OpenTelemetrySemanticsEnabled);
bytes = tagWriter.Bytes;
offset = tagWriter.Offset;
count += tagWriter.Count;
Expand Down
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