chore: envoy client + tunnel slop

[NathanFlurry]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[railway-app]

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[NathanFlurry]

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This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• chore: envoy client + tunnel slop #4531 👈 (View in Graphite)
• chore: envoy client #4521
• feat(pb): actors v3 #4463
• feat(ups): implement queue subs #4486
• feat(cache): add in flight deduping #4459
• fix(cache): clean up lib #4457
• fix(config): allow configuring topo dcs via map, fix pg ssl mode config #4456
• fix(api): dont 500 on cross dc response #4449
• chore: update byte units on frontend #4444
• fix: runner alloc idx logic, api auth for actor get #4443
• main

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[claude]

PR Review: Envoy Client Tunnel Implementation

This PR adds the HTTP and WebSocket tunnel module to the envoy client, replacing the TODO stub with a real implementation. The overall structure is solid — good use of staleness checks, synchronous entry creation before async spawning, and the wrapping u16 arithmetic for hibernatable WS deduplication.

Potential Bugs

1. closeTunnelRequestsForActor silently drops in-flight HTTP requests

tunnel/index.ts — When an actor stops, closeTunnelRequestsForActor removes the entry and errors the stream controller, but the spawned fetch task is still running. When it completes, the staleness check (ctx.tunnelRequests.get(key) !== capturedEntry) sees undefined !== capturedEntry and returns without sending any response. The gateway is left hanging indefinitely. Consider sending an explicit 503 before deleting the entry.

2. handleRequestAbort has the same silent-drop issue

tunnel/http.ts — handleRequestAbort removes the entry but the spawned fetch task continues. No response is ever sent to the gateway.

3. Non-Error rejection loses original error information

actor.ts:61-63 — When error is not an Error instance, the rejection wraps it in a generic message, discarding the original. Use new Error("actor start failed", { cause: error }) to preserve the root cause.

4. closeTunnelRequestsForActor does not filter by generation

The function closes all tunnel requests matching actorId regardless of generation. If an old generation's stop completes while a new generation already has active connections, those newer connections will also be closed. Filtering by entry.generation === generation would be safer.

Minor Issues

5. TextEncoder allocated on every string send

websocket.ts — new TextEncoder().encode(data).byteLength > MAX_PAYLOAD_SIZE allocates a full encoder and encodes the string just to get byte length. Use a module-level singleton TextEncoder.

6. sendTunnelMessageRaw always uses messageIndex 0

tunnel/index.ts — Hardcoded to messageIndex: 0 for one-shot error responses. This appears intentional (no prior messages on this request path), but a short comment confirming the invariant would prevent future confusion.

7. Warning noise in resendBufferedTunnelMessages

After reconnect, sendTunnelMessage warns if an entry was removed while disconnected. Functionally correct but can produce noisy logs during normal shutdown-while-disconnected scenarios.

8. as any on streaming Request construction

http.ts — The duplex: "half" as any cast is necessary because TypeScript does not include duplex in RequestInit. A comment explaining this would make it less surprising to reviewers.

9. URL host inconsistency

HTTP requests use http://localhost${path}, WebSocket requests use http://actor${path}. If this is intentional (e.g. for routing differentiation in the config callback), a comment explaining why would help.

Tests

The PR checklist has "I have added tests" unchecked. Given the complexity of tunnel buffering, reconnect resend logic, and hibernatable WebSocket sequencing (wrapping u16 arithmetic), test coverage would be valuable. Flagging since this is a draft.

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The main items worth addressing before merging are the silent HTTP response drop on actor stop/abort (items 1 and 2) and the generation filtering in closeTunnelRequestsForActor (item 4).