[OpenTelemetry] Add OnEnding span processor functionality #6617

majanjua-amzn · 2025-10-16T22:42:39Z

Fixes: N/A
Design discussion issue: open-telemetry/opentelemetry-specification#4024

Changes

Changes based loosely on the same changes made to opentelemetry-java: open-telemetry/opentelemetry-java#6367

This change creates a new ExtendedBaseProcessor that allows users to implement onEnding functionality to their processor, as per the spec: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#onending

Specific changes:

Changed CompositeProcessor to be extended from the new ExtendedBaseProcessor to support processors that have OnEnding
Created new ExtendedBaseProcessor as the place where this functionality is added, so as to not break any current experience of extending the normal BaseProcessor
Updated TestActivityProcessor to extend the new OnEnding method while being agnostic to it for tests that don't need it
Updated unit tests to verify the running order of the span lifecycle is correct and includes the OnEnding invocation

Merge requirement checklist

CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
Unit tests added/updated
Appropriate CHANGELOG.md files updated for non-trivial changes
Changes in public API reviewed (if applicable)

codecov · 2025-10-21T05:14:56Z

Codecov Report

❌ Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 86.76%. Comparing base (94b98e2) to head (92fa740).
⚠️ Report is 6 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/OpenTelemetry/ExtendedBaseProcessor.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6617      +/-   ##
==========================================
+ Coverage   86.73%   86.76%   +0.02%     
==========================================
  Files         258      259       +1     
  Lines       11958    11976      +18     
==========================================
+ Hits        10372    10391      +19     
+ Misses       1586     1585       -1

Flag	Coverage Δ
unittests-Project-Experimental	`86.75% <94.44%> (+0.08%)`	⬆️
unittests-Solution	`86.44% <94.44%> (-0.23%)`	⬇️
unittests-UnstableCoreLibraries-Experimental	`86.07% <ø> (-0.37%)`	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/OpenTelemetry/CompositeProcessor.cs	`95.83% <100.00%> (+0.24%)`	⬆️
src/OpenTelemetry/Trace/TracerProviderSdk.cs	`99.38% <100.00%> (+0.02%)`	⬆️
src/OpenTelemetry/ExtendedBaseProcessor.cs	`0.00% <0.00%> (ø)`

... and 3 files with indirect coverage changes

Kielek · 2025-10-21T06:10:01Z

This feature is still in development phase. It means that we cannot include it into stable releases for this package.
We have possibility to make it happen for unstable versions.

You can make full search for OTEL1000 in this repository. In this way you can find an example how to implement conditional compilation + required documentation.
OTEL1005 is the first available code at the moment.

Another thing for consideration: double check if it is not breaking change on binary level when you are introducing new class to the inheritance.

majanjua-amzn · 2025-10-24T16:40:59Z

I think I've appropriately added the OTEL1005 label where needed, could I get some help rerunning the workflows to see if there are any other remaining issues?

And regarding the following, is there a way to do so besides just running the build/tests? Thanks in advance

Another thing for consideration: double check if it is not breaking change on binary level when you are introducing new class to the inheritance.

github-actions · 2025-11-01T03:31:08Z

This PR was marked stale due to lack of activity and will be closed in 7 days. Commenting or pushing will instruct the bot to automatically remove the label. This bot runs once per day.

This change creates a new ExtendedBaseProcessor that allows users to implement onEnding functionality to their processor, as per the spec: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#onending

majanjua-amzn · 2025-11-13T20:55:43Z

Could I get some help with running the workflows and receiving a review? Thanks

martincostello · 2025-11-14T08:36:11Z

src/OpenTelemetry/ExtendedBaseProcessor.cs

+#pragma warning disable CA1012 // Abstract types should not have public constructors
+public abstract class ExtendedBaseProcessor<T> : BaseProcessor<T>
+#pragma warning restore CA1012 // Abstract types should not have public constructors


This should be fixed by adding an explicit protected constructor.

martincostello · 2025-11-14T08:36:48Z

docs/diagnostics/experimental-apis/OTEL1005.md

+
+## Overview
+
+This is an experimental API for modifying spans before they end/close


Suggested change

This is an experimental API for modifying spans before they end/close

This is an experimental API for modifying spans before they end/close.

martincostello · 2025-11-14T08:37:07Z

docs/diagnostics/experimental-apis/OTEL1005.md

+#### ExtendedBaseProcessor
+
+The abstract class `ExtendedBaseProcessor` provides an extension of the
+`BaseProcessor` that allows spans to be modified before they end as per the


Suggested change

`BaseProcessor` that allows spans to be modified before they end as per the

`BaseProcessor` class that allows spans to be modified before they end as per the

martincostello · 2025-11-14T08:37:14Z

docs/diagnostics/experimental-apis/OTEL1005.md

+
+The abstract class `ExtendedBaseProcessor` provides an extension of the
+`BaseProcessor` that allows spans to be modified before they end as per the
+OpenTelemetry specification. It provides the `OnEnding` function that is called


Suggested change

OpenTelemetry specification. It provides the `OnEnding` function that is called

OpenTelemetry specification. It provides the `OnEnding` method that is called

martincostello · 2025-11-14T08:37:29Z

docs/diagnostics/experimental-apis/OTEL1005.md

+`BaseProcessor` that allows spans to be modified before they end as per the
+OpenTelemetry specification. It provides the `OnEnding` function that is called
+during the span `End()` operation. The end timestamp MUST have been computed
+(the `OnEnding` method duration is not included in the span duration). The Span


Suggested change

(the `OnEnding` method duration is not included in the span duration). The Span

(the `OnEnding` method duration is not included in the span duration). The `Span`

martincostello · 2025-11-14T08:40:26Z

src/OpenTelemetry/CompositeProcessor.cs

 /// </summary>
 /// <typeparam name="T">The type of object to be processed.</typeparam>
+#if EXPOSE_EXPERIMENTAL_FEATURES
+public class CompositeProcessor<T> : ExtendedBaseProcessor<T>


Checked the documentation and it should be OK to change the base class without making a breaking change as all the members in the new class aren't abstract.

martincostello · 2025-11-14T08:42:19Z

src/OpenTelemetry/CompositeProcessor.cs

+        for (var cur = this.Head; cur != null; cur = cur.Next)
+        {
+            if (typeof(ExtendedBaseProcessor<T>).IsAssignableFrom(cur.Value.GetType()))
+            {
+                ((ExtendedBaseProcessor<T>)cur.Value).OnEnding(data);
+            }
+        }


Would this work to avoid reflection and casting?

Suggested change

for (var cur = this.Head; cur != null; cur = cur.Next)

{

if (typeof(ExtendedBaseProcessor<T>).IsAssignableFrom(cur.Value.GetType()))

{

((ExtendedBaseProcessor<T>)cur.Value).OnEnding(data);

}

}

for (var current = this.Head; current != null; cur = current.Next)

{

if (current.Value is ExtendedBaseProcessor<T> processor)

{

processor.OnEnding(data);

}

}

martincostello · 2025-11-14T08:43:05Z

src/OpenTelemetry/ExtendedBaseProcessor.cs

+    /// The started telemetry object.
+    /// </param>
+    /// <remarks>
+    /// This function is called synchronously on the thread which ended


Suggested change

/// This function is called synchronously on the thread which ended

/// This method is called synchronously on the thread which ended

martincostello · 2025-11-14T08:43:43Z

src/OpenTelemetry/Trace/TracerProviderSdk.cs

+                    if (typeof(ExtendedBaseProcessor<Activity>).IsAssignableFrom(this.processor?.GetType()))
+                    {
+                        (this.processor as ExtendedBaseProcessor<Activity>)?.OnEnding(activity);
+                    }


Suggested change

if (typeof(ExtendedBaseProcessor<Activity>).IsAssignableFrom(this.processor?.GetType()))

{

(this.processor as ExtendedBaseProcessor<Activity>)?.OnEnding(activity);

}

if (this.processor is ExtendedBaseProcessor<Activity> extended)

{

extended.OnEnding(activity);

}

martincostello · 2025-11-14T08:44:05Z

src/OpenTelemetry/Trace/TracerProviderSdk.cs

+                    if (typeof(ExtendedBaseProcessor<Activity>).IsAssignableFrom(this.processor?.GetType()))
+                    {
+                        (this.processor as ExtendedBaseProcessor<Activity>)?.OnEnding(activity);
+                    }


Suggested change

if (typeof(ExtendedBaseProcessor<Activity>).IsAssignableFrom(this.processor?.GetType()))

{

(this.processor as ExtendedBaseProcessor<Activity>)?.OnEnding(activity);

}

if (this.processor is ExtendedBaseProcessor<Activity> extended)

{

extended.OnEnding(activity);

}

cijothomas · 2025-11-19T14:53:37Z

src/OpenTelemetry/CHANGELOG.md

 * Add support for .NET 10.0.
  ([#6307](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6307))

+* feat: add on ending span processor functionality


https://github.com/open-telemetry/opentelemetry-dotnet/tree/main/docs/trace/extending-the-sdk#processor

Please improve this document to talk about when users should implement OnEnd vs the new option.
I am not sure of the answer given .NET's use of Activity to represent span. This must be clear to avoid user confusion once this is released.

cijothomas

Requesting changes to make sure this is actually needed. While the Spec newly added OnEnding to allow Span modification, OTel .NET uses Activity to represent span, which has slightly different semantics than the spec. And Activity is already writeable in OnEnd.

Do we need this in OTel .NET at all? If yes, please list the reason(s) before adding this.

majanjua-amzn requested a review from a team as a code owner October 16, 2025 22:42

github-actions bot added the pkg:OpenTelemetry Issues related to OpenTelemetry NuGet package label Oct 16, 2025

majanjua-amzn force-pushed the main branch 4 times, most recently from 85231aa to e108c44 Compare October 20, 2025 20:46

majanjua-amzn force-pushed the main branch from e108c44 to 26b1ce0 Compare October 23, 2025 23:24

github-actions bot added infra Infra work - CI/CD, code coverage, linters documentation Documentation related labels Oct 23, 2025

majanjua-amzn force-pushed the main branch 2 times, most recently from f176ccd to e1a2717 Compare October 24, 2025 16:38

github-actions bot added the Stale Issues and pull requests which have been flagged for closing due to inactivity label Nov 1, 2025

Kielek added keep-open Prevents issues and pull requests being closed as stale and removed Stale Issues and pull requests which have been flagged for closing due to inactivity labels Nov 4, 2025

majanjua-amzn force-pushed the main branch from 9d85d73 to b4d8354 Compare November 12, 2025 23:23

majanjua-amzn force-pushed the main branch from b4d8354 to 92fa740 Compare November 12, 2025 23:45

martincostello reviewed Nov 14, 2025

View reviewed changes

martincostello changed the title ~~feat: add on ending span processor functionality~~ [OpenTelemetry] Add OnEnding span processor functionality Nov 14, 2025

cijothomas reviewed Nov 19, 2025

View reviewed changes

cijothomas requested changes Nov 19, 2025

View reviewed changes


		## Overview

		This is an experimental API for modifying spans before they end/close

	`BaseProcessor` that allows spans to be modified before they end as per the
	`BaseProcessor` class that allows spans to be modified before they end as per the

	OpenTelemetry specification. It provides the `OnEnding` function that is called
	OpenTelemetry specification. It provides the `OnEnding` method that is called

	(the `OnEnding` method duration is not included in the span duration). The Span
	(the `OnEnding` method duration is not included in the span duration). The `Span`

	/// This function is called synchronously on the thread which ended
	/// This method is called synchronously on the thread which ended

[OpenTelemetry] Add OnEnding span processor functionality #6617

Are you sure you want to change the base?

[OpenTelemetry] Add OnEnding span processor functionality #6617

Conversation

majanjua-amzn commented Oct 16, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Changes

Merge requirement checklist

Uh oh!

codecov bot commented Oct 21, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Codecov Report

Uh oh!

Kielek commented Oct 21, 2025

Uh oh!

majanjua-amzn commented Oct 24, 2025

Uh oh!

github-actions bot commented Nov 1, 2025

Uh oh!

majanjua-amzn commented Nov 13, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

cijothomas left a comment

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

majanjua-amzn commented Oct 16, 2025 •

edited

Loading

codecov bot commented Oct 21, 2025 •

edited

Loading