feat(engine): rust runner

[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

[NathanFlurry]

• DO NOT MERGE: sandbox benches #4597 : 2 dependent PRs (#4599 , #4600 )
• fix(envoy-client): add tls #4595
• chore: fix driver test suite #4591
• chore: tunnel auth #4588
• chore: remove udb as a dependency of envoy-client #4587
• chore: revert actor v2 hack #4586
• fix: fix pool metadata protocol version refresh, rivetkit native ws #4585
• feat: US-001 - Define SqliteKv trait in rivetkit-sqlite-native #4584
• feat(rust/engine-runner): minimal rust engine runner #4289
• chore: delete kv channel #4583
• feat(engine): rust runner #4582 👈 (View in Graphite)
• chore: remove non-engine drivers #4574 : 1 other dependent PR (#4581 )
• feat: dynamic actors #4397
• fix: driver test suite & sqlite reliability #4559
• fix: remove serverless token #4572
• fix: misc token fixes #4569
• fix(pb): clean up actor stop decision handling #4566
• fix(envoy): use global instance, add signal handlers #4565
• chore: misc fixes, add pb snapshot test #4561
• fix(cache): make in memory cache global #4560
• main

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[claude]

PR Review: feat(engine): rust runner

This is a significant architectural refactor that:

• Introduces a Rust-based test envoy (engine/sdks/rust/test-envoy) replacing the TypeScript one
• Creates @rivetkit/engine-runner and @rivetkit/engine-runner-protocol as new TypeScript packages
• Moves runner-protocol from engine/sdks/rust/runner-protocol to engine/packages/runner-protocol
• Switches datacenter config from array to map format

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Critical: No integration test coverage

rivetkit-typescript/packages/engine-runner/tests/lifecycle.test.ts is entirely commented out. This leaves the new TypeScript runner without any integration tests. These should either be wired up before merging or tracked as a follow-up with a clear TODO referencing the blocker.

---

Performance: Arc<Mutex<HashMap>> throughout envoy.rs

Per CLAUDE.md: "ALWAYS prefer a dedicated concurrency container like scc::HashMap or moka::Cache over Arc<Mutex<HashMap<_,_>>>".

Several fields in Envoy use this pattern:

• actors: Arc<Mutex<HashMap<String, ActorState>>>
• actor_event_indices: Arc<Mutex<HashMap<String, i64>>>
• kv_pending_requests: Arc<Mutex<HashMap<u32, oneshot::Sender<...>>>>
• tunnel_requests: Arc<Mutex<HashMap<String, TunnelRequestState>>>

Even for test code this guideline exists to avoid contention bugs surfacing differently in test vs prod. Consider scc::HashMap or note that this is intentional test-only code.

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Performance: Linear scan in Tunnel::requestToActor

In tunnel.ts, #requestToActor is an Array<{gatewayId, requestId, actorId}> searched linearly (O(n)) when routing requests to actors. Under any non-trivial actor count this will degrade. Use a Map<string, string> keyed on a concatenation of idToStr(gatewayId) and idToStr(requestId).

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Unused constant

In src/mod.ts:

const KV_EXPIRE: number = 30_000;

This constant is declared but does not appear to be used anywhere in the file. Remove it or wire it up.

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PROTOCOL_VERSION sync

src/mod.ts declares const PROTOCOL_VERSION: number = 7 as a private constant. Make sure the value is kept in sync with PROTOCOL_MK2_VERSION in engine/packages/runner-protocol/src/lib.rs (path moved in this PR).

---

Hardcoded commit hash in comment

In tunnel.ts there is a comment referencing a specific commit hash URL. Pinning a comment to a specific commit hash will rot quickly. Reference the file path instead.

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Datacenter config: breaking format change

All config.jsonc files change "datacenters" from an array to a map. This is a silent breaking change for anyone running self-hosted with a config file not under version control. If the engine config parser does not accept both formats, document this migration explicitly.

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Minor: anyhow! vs .context()

In test_runner.rs, RunnerConfigBuilder::build uses .ok_or_else(|| anyhow::anyhow!("...")) while EnvoyConfigBuilder::build already uses .context("...") correctly. Per CLAUDE.md, prefer .context() over anyhow!.

---

Nit: u64 key format padding

In test_runner.rs:

format!("key-{:012x}", rand::random::<u64>())

u64 produces up to 16 hex digits; :012x pads to only 12. Use :016x for a correctly padded hex representation of a u64.

---

Overall the restructuring is clean and the Rust test-envoy is a clear improvement over the TypeScript one. The adapter layer in test_runner.rs maintaining backwards compatibility for existing engine tests is a good pattern. The main concern before merging is restoring integration test coverage in lifecycle.test.ts.

[MasterPtato]

Merge activity

• Apr 8, 8:52 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Apr 8, 9:15 PM UTC: Graphite rebased this pull request as part of a merge.
• Apr 8, 9:16 PM UTC: @MasterPtato merged this pull request with Graphite.