TODO: ktichen sink counter latency

[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]

Warning

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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• TODO: ktichen sink counter latency #5051 👈 (View in Graphite)
• fix(rivetkit): use engine actor stop threshold for shutdown #5049
• DO NOT MERGE: serverless restart race condition #4997
• fix(rivetkit): exit pid1 after signal shutdown #5045
• fix(rivetkit-core): decrement active actor metrics #5044
• fix(envoy-client): dont abort drain after 20s #5043
• temp: patch wasm-pack to point to latest binary #5037
• fix(rivetkit): require engine ping for health #5022
• feat(rivetkit): add current actor metrics #5020
• feat(rivetkit): expose low-cardinality metrics routes #5019
• docs(serverless): document timeout tuning #5018
• feat(kitchen-sink): add load testing harness #5017
• fix(rivetkit): expose client actor metadata #5016
• fix(runtime): avoid bounded dispatch channel stalls #5015
• fix(sqlite): fence remote requests by generation #5014
• feat(rivetkit-core): expose metrics endpoint #5013
• WIP: counter latency monitor #5011
• main

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[claude]

Code Review

This PR adds a Rust counter-latency load-test tool, renames the default runner pool from "default" to "k8s" throughout, and makes several kitchen-sink example improvements (Dockerfile PID 1 fix, WebSocket echo on the counter actor, onSleepStarted broadcast).

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Issues

Pool rename inconsistency (bug)

examples/kitchen-sink/scripts/on-sleep-remote-watch.ts (the new file) defaults to "default" at POOL_NAME = stringFromConfig("pool", ["RIVET_POOL"], "default") while the entire rest of the PR renames that default to "k8s". This new script will silently target the wrong pool when RIVET_POOL is unset.

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eprintln! in Rust code (args.rs, main.rs)

CLAUDE.md: "Never use eprintln! or println! for logging in Rust code. Always use tracing::info!, tracing::warn!, tracing::error!, etc."

EnvConfig::from_env() uses eprintln! + process::exit(1) for fatal errors. It should return anyhow::Result<Self> so the caller controls the exit path and errors go through tracing.

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Mutex<HashMap> in stats.rs

CLAUDE.md: "Never use Mutex<HashMap<...>> or RwLock<HashMap<...>>. Use scc::HashMap."

State::worker_health is a Mutex<HashMap<WorkerId, WorkerHealth>>. The lock is not held across awaits so there is no deadlock risk, but the pattern violates the codebase invariant. Adding scc as a dependency and switching to scc::HashMap would resolve it.

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Magic number 1 for WebSocket ready state (counter.ts, sigterm-sleep-probe.ts)

websocket.readyState !== 1 uses a bare integer where WebSocket.OPEN (or a named constant) is clearer and prevents silent mismatch.

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Em dashes and sentence fragments in comments

CLAUDE.md: "Do not use em dashes. Use periods to separate sentences instead."

counter.ts comment block contains both an arrow character and an em dash. Suggested rewrite: "Plain echo for the rtt counter-latency harness. Any message received is sent back immediately with no state mutation or awaits, to keep the echo path as close to raw WebSocket RTT as possible."

Same fragment/dash pattern appears in file-level comments in args.rs, concurrent.rs, and endpoint.rs.

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Duplicate base36 implementation

rtt.rs defines base36(n: u64) -> String and concurrent.rs defines to_base36(n: u64) -> String with identical logic and different names. These should be consolidated in a shared util.rs module.

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TOCTOU race in sigterm-sleep-probe.ts broadcast

websocket.send() can throw if the socket transitions to CLOSING between the readyState !== 1 guard and the actual send. A try/catch removes the race window.

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Minor notes

• RIVET_PROTOCOLS constant in ws.rs is defined but unused and will produce a compiler warning.
• endpoint.rs reimplements percent-encoding manually; the url crate (already a dependency) exposes percent_encoding::percent_decode_str. The manual + to space translation applies HTML form-encoding semantics that are incorrect for URL auth/path components.
• The Dockerfile CMD comment uses an arrow character and a comma splice; period-separated sentences would follow CLAUDE.md comment style.