Fill out implementation for health check

[andrewnitu]

Description

Implement the placeholder health check function.

Changes Made

• Modify the health check function to return healthy when all of the below conditions are met:
  • inference executor is running
  • websocket with livekit server is open

Pre-Review Checklist

• Build passes: All builds (lint, typecheck, tests) pass locally
• AI-generated code reviewed: Removed unnecessary comments and ensured code quality
• Changes explained: All changes are properly documented and justified above
• Scope appropriate: All changes relate to the PR title, or explanations provided for why they're included
• Video demo: A small video demo showing changes works as expected and did not break any existing functionality using Agent Playground (if applicable)

Testing

• All tests pass
• running node ./examples/src/basic_agent.ts dev locally
  • if livekit URL is wrong, it can't connect, so health check fails
  • if livekit URL is correct, health check passes
• Make sure both restaurant_agent.ts and realtime_agent.ts work properly (for major changes)

Additional Notes

---

Note to reviewers: Please ensure the pre-review checklist is completed before starting your review.

Summary by CodeRabbit

• New Features

  • Health endpoint now reports live system status with clear diagnostic messages.
  • Server accepts a pluggable health provider so root-status responses reflect actual runtime state.
  • Added a process liveness indicator that reflects runtime and connection health.

• Refactor

  • Root status handling updated to use the new health provider and return accurate HTTP status codes.

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Latest commit: f8b0605

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[coderabbitai]

📝 Walkthrough

Walkthrough

Introduces a dynamic health check: new exported HealthCheckResult, HTTPServer constructor now accepts a healthCheckListener, root handler returns 200/503 based on health, adds isAlive getter to SupervisedProc, and worker passes a health function that checks inference process and LiveKit connection. (≤50 words)

Changes

Cohort / File(s)	Summary
HTTP Server API Enhancement agents/src/http_server.ts	Added export interface HealthCheckResult { healthy: boolean; message: string }. Changed HTTPServer constructor signature to accept healthCheckListener: () => HealthCheckResult before workerListener. Root / handler now uses health result to return 200 or 503 with the message.
Process Monitoring agents/src/ipc/supervised_proc.ts	Added public getter get isAlive(): boolean that returns true when the process started, not closing, and its IPC channel is connected.
Worker Health Check Implementation agents/src/worker.ts	Replaced static health payload with a dynamic health() passed to HTTPServer. health() checks: if inference executor missing or not alive → { healthy: false, message: 'inference process not running' }; if not connected to LiveKit → { healthy: false, message: 'not connected to livekit' }; else { healthy: true, message: 'OK' }.

Sequence Diagram(s)

sequenceDiagram
  participant Client as Client
  rect rgba(200,220,255,0.5)
    participant HTTP as HTTPServer
  end
  rect rgba(200,255,200,0.5)
    participant Proc as InferenceProc (SupervisedProc)
    participant LK as LiveKitConnector
  end

  Client->>HTTP: GET /
  HTTP->>HTTP: invoke healthCheckListener()
  HTTP->>Proc: check isAlive
  Proc-->>HTTP: isAlive (true/false)
  HTTP->>LK: check connection state
  LK-->>HTTP: connected (true/false)
  alt healthy
    HTTP-->>Client: 200 OK + message
  else unhealthy
    HTTP-->>Client: 503 Service Unavailable + message
  end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 I peeked at processes, ears all perked and bright,
Pondered LiveKit whispers in the quiet night,
If the proc is hopping and the session's near,
I'll chirp "OK!" — else thump a gentle fear.
🥕✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description includes main sections (Description, Changes Made, Pre-Review Checklist, Testing) with relevant details about the health check implementation and testing performed locally.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title 'Fill out implementation for health check' directly and accurately describes the main change—implementing the health check function that was previously a placeholder.

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✨ Finishing touches

• 📝 Generate docstrings

---

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@agents/src/worker.ts`:
- Around line 351-354: The health check currently treats an existing `#session`
object as "connected" even if the WebSocket is closed; update the condition in
the health check to verify the socket's readyState (e.g., check that
this.#session exists and this.#session.readyState === WebSocket.OPEN or
readyState === 1) instead of solely checking !this.#session, keeping the
surrounding checks for this.#closed and this.#connecting intact (refer to the
fields `#session`, `#closed`, `#connecting` and the health-checking block in the
worker). Ensure you guard access to readyState by confirming this.#session is
truthy before reading it and use the WebSocket.OPEN constant (or numeric 1) so
closed/closing states are treated as unhealthy.

📜 Review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 15dd71b and 804162f.

📒 Files selected for processing (3)

• agents/src/http_server.ts
• agents/src/ipc/supervised_proc.ts
• agents/src/worker.ts

🧰 Additional context used

📓 Path-based instructions (3)

**/*.{ts,tsx,js,jsx}

📄 CodeRabbit inference engine (.cursor/rules/agent-core.mdc)

Add SPDX-FileCopyrightText and SPDX-License-Identifier headers to all newly added files with '// SPDX-FileCopyrightText: 2025 LiveKit, Inc.' and '// SPDX-License-Identifier: Apache-2.0'

Files:

• agents/src/ipc/supervised_proc.ts
• agents/src/http_server.ts
• agents/src/worker.ts

**/*.{ts,tsx}?(test|example|spec)

📄 CodeRabbit inference engine (.cursor/rules/agent-core.mdc)

When testing inference LLM, always use full model names from agents/src/inference/models.ts (e.g., 'openai/gpt-4o-mini' instead of 'gpt-4o-mini')

Files:

• agents/src/ipc/supervised_proc.ts
• agents/src/http_server.ts
• agents/src/worker.ts

**/*.{ts,tsx}?(test|example)

📄 CodeRabbit inference engine (.cursor/rules/agent-core.mdc)

Initialize logger before using any LLM functionality with initializeLogger({ pretty: true }) from '@livekit/agents'

Files:

• agents/src/ipc/supervised_proc.ts
• agents/src/http_server.ts
• agents/src/worker.ts

🧬 Code graph analysis (1)

agents/src/worker.ts (1)

agents/src/http_server.ts (1)

• HTTPServer (20-76)

🔇 Additional comments (4)

agents/src/ipc/supervised_proc.ts (1)

62-64: LGTM!

The isAlive getter correctly combines the three essential conditions for determining process health: started, not closing, and IPC channel connected. The optional chaining with double negation ensures a proper boolean return.

agents/src/worker.ts (1)

358-365: LGTM!

The worker listener callback cleanly provides the required metadata with proper enum-to-string conversion for worker_type.

agents/src/http_server.ts (2)

7-10: LGTM!

Clean and minimal interface definition for health check results.

---

26-52: LGTM!

The constructor signature update and route handler logic correctly implement the dynamic health check mechanism. The 503 status for unhealthy states follows standard HTTP semantics for service availability.

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