[codex] Fix driver error monitoring

[Alb3e3]

Summary

• add a shared driver monitor that polls driver tasks by completion order
• use it from both serve and daemon so driver failures are observed promptly
• add a regression test for a later failing driver sitting behind an earlier long-running driver

Root cause

serve and daemon collected driver join handles in a FuturesUnordered, but then awaited each join handle from the collection iterator. That made failures depend on insertion order rather than completion order. If an earlier driver kept running and a later Ouroboros Unix socket driver failed to bind, the bind error could remain unread until shutdown.

Fixes #293.

Bounty note

I linked Githoney bounty 64 from #293 with /githoney link-bounty --bountyId 64. The issue bot comment shows a 2025-01-26 deadline, so please confirm whether it is still claimable.

Verification

• cargo test monitor_drivers_observes_later_failures_before_waiting_for_earlier_drivers --no-default-features
• cargo test --no-default-features
• git diff --check

I also tried cargo fmt --check, but this checkout has pre-existing rustfmt drift outside this PR on stable rustfmt, so I left those unrelated files untouched.

Summary by CodeRabbit

• Bug Fixes

  • Improved driver failure detection to respond promptly to errors without waiting for unrelated tasks to complete.

• Refactor

  • Unified driver monitoring and error handling logic across service configurations for consistency.

[Alb3e3]

/githoney link-bounty --bountyId 64

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 7aaf0a61-c249-4229-a90b-4b2c15129044

📥 Commits

Reviewing files that changed from the base of the PR and between 6136eac and ba00b6c.

📒 Files selected for processing (3)

• src/bin/dolos/common.rs
• src/bin/dolos/daemon.rs
• src/bin/dolos/serve.rs

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📝 Walkthrough

Walkthrough

Centralizes driver task monitoring across daemon and serve entry points by extracting inline error-handling logic into a shared monitor_drivers function. The function iterates FuturesUnordered driver tasks, logs failures, and cancels the exit token when any driver fails, with a test validating prompt detection of later failures.

Changes

Driver monitoring refactor

Layer / File(s)	Summary
monitor_drivers implementation and test src/bin/dolos/common.rs	Adds imports for FuturesUnordered, StreamExt, JoinHandle, and expanded tracing levels. Implements async monitor_drivers that awaits driver task handles, ignores successes, and cancels the exit token on any error or join failure. Includes test verifying the function detects a later failure before waiting on a slow earlier task.
daemon.rs integration src/bin/dolos/daemon.rs	Updates tracing imports to remove error (now handled in monitor_drivers). Replaces inline loop over driver results with a single call to monitor_drivers.
serve.rs integration src/bin/dolos/serve.rs	Removes direct tracing::error import. Replaces local async control flow awaiting each driver with a call to monitor_drivers.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• scarmuega

Poem

A rabbit refactors with care and delight, 🐰
Three drivers now monitored—centralized right!
Failures are caught at one shared checkpoint,
No code duplication, no logic misdirect.
One helper to guide them when things go amiss!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title '[codex] Fix driver error monitoring' accurately describes the main change: adding a shared driver monitor function to fix driver error detection ordering.
Linked Issues check	✅ Passed	The PR addresses the core technical requirement from #293 by implementing prompt detection of driver failures through a monitor_drivers function that observes failures by completion order rather than insertion order.
Out of Scope Changes check	✅ Passed	All changes are in-scope: monitor_drivers function implementation, integration into serve and daemon, and regression test are all aligned with fixing driver error monitoring.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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