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feat(otel): add otel tracing for standalone activities. #647

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Merged
jmaeagle99 merged 6 commits into from
May 27, 2026
Merged

feat(otel): add otel tracing for standalone activities. #647

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23bdf63
feat(otel): add otel tracing for standalone activities.
cconstable Apr 22, 2026
116906f
style(tests): using discard variable to signal intent
cconstable Apr 23, 2026
df03b01
fix(tests): use two activities for testing cancel and terminate activ…
cconstable Apr 23, 2026
6c3d6a2
feat(otel): remove tracing for everything except start_activity for c…
cconstable May 11, 2026
9997d21
fix(tests): use a different name for the saa so the span doesn't conf…
cconstable May 11, 2026
65ceb90
Merge branch 'main' into cc/standalone-activity-tracing
jmaeagle99 May 27, 2026
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40 changes: 40 additions & 0 deletions src/Temporalio.Extensions.OpenTelemetry/TracingInterceptor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -231,6 +231,21 @@ protected virtual IDictionary<string, string> HeadersFromContext(
return ret;
}

/// <summary>
/// Create tag collection for the given standalone activity ID.
/// </summary>
/// <param name="activityId">Standalone activity ID.</param>
/// <returns>Tags.</returns>
protected virtual IEnumerable<KeyValuePair<string, object?>> CreateStandaloneActivityTags(
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@cconstable cconstable May 11, 2026

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I could just inline this logic now that start_activity is the only event we are adding tracing to.

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@jmaeagle99 jmaeagle99 May 11, 2026

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I think it's fine to leave here as-is. There's precedent for this pattern.

string activityId)
{
if (Options.TagNameActivityId is string name)
{
return new KeyValuePair<string, object?>[] { new(name, activityId) };
}
return Enumerable.Empty<KeyValuePair<string, object?>>();
}

private static void RecordExceptionWithStatus(Activity? activity, Exception exception)
{
// If the exception is a benign exception, we do not consider the status an error. Note,
Expand Down Expand Up @@ -394,6 +409,31 @@ public override async Task<WorkflowUpdateHandle<TResult>> StartWorkflowUpdateAsy
}
}

public override async Task<ActivityHandle<TResult>> StartActivityAsync<TResult>(
StartActivityInput input)
{
using (var activity = ClientSource.StartActivity(
$"StartActivity:{input.Activity}",
kind: ActivityKind.Client,
parentContext: default,
tags: input.Options.Id is string id ? root.CreateStandaloneActivityTags(id) : null))
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@cconstable cconstable Apr 23, 2026

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input.Options.Id is optional because it uses the shared StartActivityInput. AFAICT, it will never be null for standalone activities.

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@jmaeagle99 jmaeagle99 May 11, 2026

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It shouldn't be null (and is documented that it is required), but customers can still pass null. Given the current type declaration, you are doing the right thing here. The validation of the value is done within the innermost interceptor, which hasn't been called at this point.

{
if (HeadersFromContext(input.Headers) is Dictionary<string, Payload> headers)
{
input = input with { Headers = headers };
}
try
{
return await base.StartActivityAsync<TResult>(input).ConfigureAwait(false);
}
catch (Exception e)
{
RecordExceptionWithStatus(activity, e);
throw;
}
}
}

/// <summary>
/// Serialize current context to headers if one exists.
/// </summary>
Expand Down
23 changes: 22 additions & 1 deletion tests/Temporalio.Tests/Extensions/OpenTelemetry/TracingInterceptorTests.cs
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Expand Up @@ -797,6 +797,27 @@ public async Task TracingInterceptor_Nexus_HasTracing()
"RunWorkflow:TracingWorkflow"));
}

[Fact]
public async Task TracingInterceptor_StandaloneActivity_HasProperSpans()
{
var activityId = $"act-{Guid.NewGuid()}";
var spans = await WithTracingWorkerAsync(async (client, _) =>
{
await client.StartActivityAsync(
"TestStandaloneActivitySpans",
Array.Empty<object?>(),
new(activityId, $"standalone-tq-{Guid.NewGuid()}")
{
ScheduleToCloseTimeout = TimeSpan.FromMinutes(5),
});
});

var activityTags = new[] { ActivityAssertion.TagEqual("temporalActivityID", activityId) };
AssertActivities(
spans,
new ActivityAssertion("StartActivity:TestStandaloneActivitySpans", Parent: null, Tags: activityTags));
}

private static void AssertActivities(
IReadOnlyCollection<Activity> activities, params ActivityAssertion[] assertions)
{
Expand Down Expand Up @@ -886,7 +907,7 @@ private async Task<IReadOnlyCollection<Activity>> WithTracingWorkerAsync(
var activities = new List<Activity>();

// Setup provider
using var tracerProvider = global::OpenTelemetry.Sdk.CreateTracerProviderBuilder().
using var _ = global::OpenTelemetry.Sdk.CreateTracerProviderBuilder().
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@cconstable cconstable Apr 23, 2026

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Took me a second to realize that tracerProvider was not actually being used we were just using using for lifetime management. Swapped to discard variable instead which preserves lifetime management but better signals intent.

AddSource(
TracingInterceptor.ClientSource.Name,
TracingInterceptor.WorkflowsSource.Name,
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