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fix(tmplexec): handle race condition on tmplexec #5885

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fix(tmplexec): handle race condition on tmplexec #5885

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@babariviere babariviere commented Dec 5, 2024 •
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Proposed changes

The fix copy the lastMatcherEvent pointer to avoid a race condition where:

  1. lastMatcherEvent.Lock() is called
  2. lastMatcherEvent is changed because of a small race condition
  3. lastMatcherEvent.Unlock() failed because the mutex was never locked

This result in an error like this:

fatal error: sync: Unlock of unlocked RWMutex

Here is an example crash log:

crash.log

I don't think this should be the final fix. This should probably wait for the ScanContext to end/stop.

Checklist

  • Pull request is created against the dev branch
  • All checks passed (lint, unit/integration/regression tests etc.) with my changes
  • I have added tests that prove my fix is effective or that my feature works
  • I have added necessary documentation (if appropriate)

Summary by CodeRabbit

  • New Features

    • Enhanced error handling in the execution logic for improved robustness.
    • New mechanism to log failure events, ensuring better tracking of execution outcomes.

  • Bug Fixes

    • Addressed potential race conditions in the execution process.

  • Documentation

    • Updated comments for improved clarity on the execution flow.

@auto-assign auto-assign bot requested a review from dogancanbakir December 5, 2024 09:37
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coderabbitai bot commented Dec 5, 2024 •
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Walkthrough

The pull request introduces modifications to the TemplateExecuter class in pkg/tmplexec/exec.go, specifically enhancing the Execute method to improve thread safety and error handling. The handling of the lastMatcherEvent variable is updated to prevent race conditions by using a local pointer. Additionally, a new mechanism is implemented to log failure events when no callback is called, ensuring robustness in concurrent scenarios. While the Compile method remains unchanged, the overall structure of the Execute method is refined, and minor comment adjustments are made for clarity.

Changes

File Change Summary
pkg/tmplexec/exec.go - Modified Execute method to handle lastMatcherEvent with a local pointer to avoid race conditions.
- Introduced logging for failure events with a fakeEvent when callbacks are not called.
- Updated logic in Execute and ExecuteWithResults methods (signatures unchanged).
- Minor comment adjustments for clarity.

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A rabbit hops without delay.
With locks and pointers, safe and sound,
New logs for failures now abound!
In the code, we weave our tale,
Robust and swift, we shall not fail! 🌼

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coderabbitai bot reviewed Dec 5, 2024
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Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI
Review profile: CHILL

📥 Commits

Reviewing files that changed from the base of the PR and between 2549592 and 82c3f9a.

📒 Files selected for processing (1)
  • pkg/tmplexec/exec.go (1 hunks)

pkg/tmplexec/exec.go
Comment on lines +217 to +222
// copy lastMatcherEvent pointer to avoid race condition where lastMatcherEvent is changed after the lock.
event := lastMatcherEvent
event.Lock()
event.InternalEvent["error"] = getErrorCause(ctx.GenerateErrorMessage())
event.Unlock()
writeFailureCallback(event, e.options.Options.MatcherStatus)
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🛠️ Refactor suggestion

Refactor the workaround for handling unmatched events

The current implementation includes a workaround to handle cases where the callback is not called and matcher-status is true, as indicated by the TODO comment. This approach may lead to maintenance challenges and unexpected behaviors.

Consider refactoring this section to wait for the ScanContext to complete before proceeding. This would ensure proper synchronization and more robust handling of unmatched events.

Would you like assistance in proposing a refactored implementation for this section?

@babariviere babariviere changed the title fix(tmplexec): handle rare condition on tmplexec fix(tmplexec): handle race condition on tmplexec Dec 5, 2024
@dogancanbakir dogancanbakir requested review from dwisiswant0, tarunKoyalwar and ehsandeep and removed request for dogancanbakir December 5, 2024 11:19
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Hi @babariviere, this should come with a detailed issue report providing clear steps to reproduce it to properly understood and addressed effectively.

@babariviere
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@dwisiswant0 It's really hard to reproduce since there is really small time frame between the Lock and Unlock. Maybe a time.Sleep in-between should do the trick but I have not yet tested it, and don't have the time.

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@dwisiswant0 have you checked the [crash.log](https://github.com/user-attachments/files/18020825/crash.log) file in the initial description?

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@dwisiswant0 dwisiswant0 Awaiting requested review from dwisiswant0

@tarunKoyalwar tarunKoyalwar Awaiting requested review from tarunKoyalwar

@ehsandeep ehsandeep Awaiting requested review from ehsandeep

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4 participants
@babariviere @dwisiswant0 @gnuletik @ehsandeep