Fix RedisMessageQueue race condition by sij411 · Pull Request #532 · fedify-dev/fedify

sij411 · 2026-01-23T15:33:41Z

Summary

Fixed a race condition in RedisMessageQueue.listen() where pub/sub notifications could be missed if enqueue() was called immediately after listen() started
The message handler was attached inside an async callback, allowing a timing window where messages could be published before the handler was ready
Added deterministic regression test using mock Redis to reproduce the bug 100% of the time

Test plan

Run deno test --allow-all packages/redis/src/mq.race.test.ts - deterministic regression tests pass
Run deno test --allow-all packages/redis/src/mq.test.ts with Redis - integration test passes (requires REDIS_URL env)
Pre-commit hooks pass (lint, fmt, types)

Fixes #515

🤖 Generated with Claude Code

gemini-code-assist · 2026-01-23T15:34:01Z

Summary of Changes

Hello @sij411, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical race condition within the RedisMessageQueue's listen() method. Previously, messages could be lost due to a timing issue where the message handler was not yet active when a message was published. The fix ensures that the message handler is fully established before the listen() method proceeds, guaranteeing reliable message delivery. A dedicated, deterministic test case has been introduced to prevent future regressions of this specific issue.

Highlights

Race Condition Fix: Addressed a race condition in RedisMessageQueue.listen() where pub/sub notifications could be missed if enqueue() was called immediately after listen() started.
Root Cause Identified: The race condition was caused by the message handler being attached inside an async callback, creating a timing window where messages could be published before the handler was ready.
Solution Implemented: The listen() method now awaits the Redis subscription before synchronously attaching the message handler, ensuring no notifications are missed.
New Regression Test: A new deterministic regression test (mq.race.test.ts) has been added using a mock Redis client to reliably reproduce the bug and verify the fix.

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sij411 · 2026-01-23T15:35:20Z

/gemini review

gemini-code-assist

Code Review

This pull request effectively addresses a critical race condition in the RedisMessageQueue.listen() method, where pub/sub notifications could be missed. The fix correctly ensures that the message handler is attached synchronously after the Redis subscription is established, preventing messages from being lost during the timing window. The addition of a comprehensive and deterministic regression test suite, including a mock Redis client, is highly commendable and provides strong verification of the fix. The CHANGES.md entry clearly explains the issue and its resolution.

packages/redis/src/mq.ts

packages/redis/src/mq.race.test.ts

packages/redis/src/mq.ts

gemini-code-assist

Code Review

This pull request addresses a race condition in the RedisMessageQueue.listen() method, where pub/sub notifications could be missed if enqueue() was called immediately after listen() started. The fix involves awaiting the subscription before attaching the message handler, ensuring that no messages are missed. The pull request includes a deterministic regression test using mock Redis to reproduce the bug and verify the fix. The changes look good and the tests are well-written.

packages/redis/src/mq.ts

The message handler was attached inside an async callback, allowing a timing window where pub/sub notifications could be missed if enqueue() was called immediately after listen() started. The fix awaits subscribe() and attaches the handler synchronously. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

The unsubscribe() call was async but not awaited, causing "Connection is closed" error when disconnect() was called while unsubscribe() was still pending. The original code didn't have unsubscribe() in the abort handler - disconnect() handles cleanup. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

codecov · 2026-01-24T05:44:04Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

Files with missing lines	Coverage Δ
packages/redis/src/mq.ts	`90.14% <100.00%> (+1.98%)`	⬆️

... and 1 file with indirect coverage changes

🚀 New features to boost your workflow:

📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

…ix/redismq

gemini-code-assist bot reviewed Jan 23, 2026

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sij411 force-pushed the fix/redismq branch from 7d7de06 to 90fe9f2 Compare January 23, 2026 15:47

sij411 marked this pull request as draft January 23, 2026 17:30

sij411 and others added 2 commits January 24, 2026 14:17

Replace Deno specific functions to Node

00c3b99

Merge branch 'main' into fix/redismq

cf88fa7

sij411 marked this pull request as ready for review January 24, 2026 05:49

sij411 added 2 commits January 24, 2026 15:49

Replace @fedify/fixture to node:test for fixing broken pnpm test:node

952bcd5

Merge branch 'fix/redismq' of https://github.com/sij411/fedify into f…

4da1921

…ix/redismq

dahlia added type/bug Something isn't working type/test Testing related driver/redis Redis driver (@fedify/redis) labels Jan 24, 2026

dahlia approved these changes Jan 24, 2026

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dahlia merged commit 7f2bb1d into fedify-dev:main Jan 24, 2026
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Fix RedisMessageQueue race condition#532

Fix RedisMessageQueue race condition#532
dahlia merged 6 commits intofedify-dev:mainfrom
sij411:fix/redismq

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sij411 commented Jan 23, 2026

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