feat(worker-proxy): proxy extension gRPC calls

[Jacob Viau (jviau)]

Issue describing the changes in this PR

N/A. This is layer 3 of the WorkerProxy extension-RPC stack and follows #11959.

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)

Additional information

Layer 3 ports telemetry-free WorkerProxy extension gRPC ingress above preceding PR #11959. It relays opaque gRPC frames and metadata over the extension RPC stream, enforces transport limits, flow control, cancellation, deadlines, and status/trailer propagation. Metrics and activity enrichment remain intentionally deferred to layer 4.

[Copilot]

🟡 Changes recommended

There are compile-breaking issues in the new ingress (array sizing with uint) and the new test stub (IHttpResponseTrailersFeature missing Available).

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR adds worker-facing extension gRPC ingress to WorkerProxy by relaying opaque gRPC frames and metadata over the already-established Extension RPC stream (layer 3 of the extension-RPC stack).

Changes:

• Introduces ExtensionGrpcIngress to translate HTTP/gRPC framing + metadata into ExtensionRpcMessage start/data/half-close and to translate response headers/data/trailers back to gRPC.
• Wires the ingress into the WorkerProxy HTTP pipeline so worker-facing native gRPC calls are intercepted and proxied over the extension RPC stream.
• Adds unit tests covering basic relay, invalid framing, negotiated limit violations, deadline while negotiating, and disconnect behavior.

File summaries

File	Description
test/Functions.WorkerProxy.Tests/ExtensionGrpcIngressTests.cs	Adds unit tests for extension gRPC ingress framing, metadata propagation, limits, deadlines, and disconnect handling.
src/Functions.WorkerProxy/WorkerProxyApplication.cs	Registers ExtensionGrpcIngress and adds middleware to route eligible requests into the ingress handler.
src/Functions.WorkerProxy/ExtensionGrpcIngress.cs	Implements the ingress relay logic, including framing parsing, metadata mapping, timeout parsing, cancellation/deadline behavior, and status/trailer propagation.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 3
• Review effort level: Lite

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[Copilot]

🟡 Changes recommended

The new ingress response pump does not handle host-side Cancel messages and contains an uncaught overflow path that can fail requests without a proper gRPC status.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 2
• Review effort level: Lite

[Copilot]

🔵 Needs a closer look

The ingress currently accepts malformed grpc-timeout headers without failing the request, and per-call Information-level logs are likely too noisy under load.

Review details

Suppressed comments (3)

Previously missed (2) — in code that hasn't changed since the last review.

src/Functions.WorkerProxy/ExtensionGrpcIngress.cs:260

• If the request includes a grpc-timeout header but it’s malformed, CreateStart currently ignores it (leaving start.Timeout unset) and continues relaying the request. This can result in inconsistent behavior (no local deadline enforcement) and potentially forwards an invalid timeout value to the host side via metadata. Consider treating an invalid grpc-timeout header as a request formatting error (InvalidArgument) by throwing a FormatException when parsing fails.
  src/Functions.WorkerProxy/ExtensionGrpcIngress.cs:746
• These per-extension-call logs are currently emitted at Information level, which can be very high volume for gRPC traffic and increase log ingestion costs/noise. In the existing WorkerProxy relay, comparable lifecycle logs are Debug (e.g., FunctionRpcRelay.Session.cs uses Debug for session termination), so consider making this Debug as well (and similarly for the CallCompleted log).

This issue also appears on line 757 of the same file.

src/Functions.WorkerProxy/ExtensionGrpcIngress.cs:757

• This per-extension-call completion log is emitted at Information level and may be too chatty under load. Consider lowering to Debug to match existing WorkerProxy relay logging patterns and to avoid high-volume info logs.

            LogLevel.Information,

• Files reviewed: 3/3 changed files
• Comments generated: 0 new
• Review effort level: Lite