ActivitySource.CreateActivity and ActivitySource.StartActivity behavior change
The ActivitySource.CreateActivity and ActivitySource.StartActivity APIs only return an Activity when there's a registered listener that decides the instance should be created. This is generally known as sampling.
The System.Diagnostics.ActivitySamplingResult enum defines the possible sampling decisions.
When creating an Activity without a parent, ActivitySamplingResult drives whether the Activity is created and then how the Recorded and IsAllDataRequested properties are set:
| ActivitySamplingResult | Activity created | Activity.Recorded | Activity.IsAllDataRequested |
|---|---|---|---|
| None | No | ||
| PropagationData | Yes | False | False |
| AllData | Yes | False | True |
| AllDataAndRecorded | Yes | True | True |
It is also possible to create an Activity with a parent. The parent could be in the same process, or it could be a remote parent propagated to the current process.
Previous behavior
Previously, when creating an Activity as PropagationData with a parent marked as Recorded, the Recorded and IsAllDataRequested properties were set as follows:
| ActivitySamplingResult | Activity created | Activity.Recorded | Activity.IsAllDataRequested |
|---|---|---|---|
| PropagationData | Yes | True | False |
New behavior
Starting in .NET 10, when you create an Activity as PropagationData with a parent marked as Recorded, the Recorded and IsAllDataRequested properties are set as follows:
| ActivitySamplingResult | Activity created | Activity.Recorded | Activity.IsAllDataRequested |
|---|---|---|---|
| PropagationData | Yes | False | False |
Version introduced
.NET 10 Preview 1
Type of breaking change
This change is a behavioral change.
Reason for change
The previous behavior did not follow the OpenTelemetry specification.
Recommended action
If you've implemented ActivityListener.Sample directly AND use ActivitySamplingResult.PropagationData, verify that you're not reliant on the flawed behavior. To restore the previous behavior, you can set Activity.ActivityTraceFlags to Recorded after the CreateActivity or StartActivity call.
If you use OpenTelemetry .NET and have customized the sampler, verify your sampler configuration. The default OpenTelemetry .NET configuration uses a parent-based algorithm that isn't impacted.
