[Rohit Ranjan (RohitRanjanMS)]

Issue describing the changes in this PR

Resolves #11734

Pull request checklist

IMPORTANT: Currently, changes must be backported to the in-proc branch to be included in Core Tools and non-Flex deployments.

• Backporting to the in-proc branch is not required
  • Backport PR will follow after this change merges.
• My changes do not require documentation changes
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
• My changes do not require diagnostic events changes
• I have added all required tests (Unit tests, E2E tests)

Additional information

Registers the Azure.Messaging.ServiceBus.ServiceBusSessionProcessor activity source so session-enabled Service Bus triggers preserve W3C trace context in OpenTelemetry mode.

Validated with a private site extension against a session-enabled Service Bus trigger: the stock host omitted the session processor request and broke the producer trace, while the patched host emitted ServiceBusSessionProcessor.ProcessSessionMessage with the producer operation ID.

[Copilot]

Pull request overview

This PR addresses a distributed tracing gap in Functions Host OpenTelemetry integration by ensuring session-enabled Service Bus triggers are instrumented via the correct ActivitySource, preserving W3C trace context.

Changes:

• Added Azure.Messaging.ServiceBus.ServiceBusSessionProcessor to the host’s OpenTelemetry ActivitySource allowlist.
• Introduced a constant for the Service Bus session processor ActivitySource name.
• Added a unit test validating that an activity can be started for the session processor source (i.e., a listener is registered).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
test/WebJobs.Script.Tests/Diagnostics/OpenTelemetry/OpenTelemetryConfigurationExtensionsTests.cs	Adds coverage to validate the host listens to the Service Bus session processor ActivitySource.
src/WebJobs.Script/Diagnostics/OpenTelemetry/OpenTelemetryConstants.cs	Introduces a constant for the Service Bus session processor ActivitySource name.
src/WebJobs.Script/Diagnostics/OpenTelemetry/OpenTelemetryConfigurationExtensions.cs	Subscribes to the Service Bus session processor ActivitySource during tracing configuration.

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