Skip logging errors on expected grpc client disconnect scenarios

[kshyju]

resolves #10572

Improves handling of gRPC stream disconnections by skipping error logging when the client disconnects in an expected manner during bidirectional streaming.

• In gRPC bidirectional streaming, client disconnects are a common and expected behavior (e.g., process exit, network interruption).
• When a disconnect occurs while the server is awaiting MoveNext(), it throws an IOException wrapping a ConnectionAbortedException.
• Previously, all exceptions were logged as errors, including these expected disconnects.
• This PR adds logic to detect this specific case and skip logging it as an error if ServerCallContext.CancellationToken has been canceled.

Repro note

The only way I could reproduce this behavior was by introducing an artificial delay in cancellation token signaling.

azure-functions-host/src/WebJobs.Script.Grpc/Server/FunctionRpcService.cs

Line 36 in 2391b98

CancellationTokenRegistration ctr = cts.Token.Register(static state => ((TaskCompletionSource<bool>)state).TrySetResult(false), cancelSource);

Specifically, a Task.Delay(100) was added before completing the TaskCompletionSource to simulate a race condition.

CancellationTokenRegistration ctr = cts.Token.Register(static async state =>
{
    await Task.Delay(100);
    ((TaskCompletionSource<bool>)state).TrySetResult(false);
}, cancelSource);

This causes MoveNext() to enter before cancellation is signaled, triggering the exception in a realistic edge case.

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
  • Otherwise: Link to backporting PR
• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• 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
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

[Copilot]

Pull Request Overview

Improves handling of gRPC bidirectional streaming by ignoring expected client disconnect exceptions instead of logging them as errors.

• Adds a specialized catch for IOException with an inner ConnectionAbortedException when the server call’s cancellation token is already canceled.
• Imports the required namespaces (System.IO, Microsoft.AspNetCore.Connections) for the new exception handling.
• Updates release_notes.md to document the change.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/WebJobs.Script.Grpc/Server/FunctionRpcService.cs	Added a conditional catch block to suppress logging on expected client disconnect.
release_notes.md	Noted the new behavior for skipping error logging on gRPC client disconnect.

Comments suppressed due to low confidence (2)

src/WebJobs.Script.Grpc/Server/FunctionRpcService.cs:79

• This new error-handling path isn't covered by existing tests; consider adding a unit test that simulates a client disconnect to verify no error is logged when the cancellation token is canceled.

            catch (IOException ex) when (ex.InnerException is ConnectionAbortedException && context.CancellationToken.IsCancellationRequested)

src/WebJobs.Script.Grpc/Server/FunctionRpcService.cs:85

• In an async method returning a boolean result, an empty return; may default to false or cause a compile error. Consider returning false explicitly to make the intention clear and ensure correct behavior.

                return;