Improved aio handling in SubtocPreloader

[Ozaq]

Description

Improved aio handling in SubtocPreloader

Now suspends for up to 1 sec, then logs stall and retries.

Also addresses missing error handling and cancellation on exception
throwing.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

🌈🌦️📖🚧 Documentation FDB 🚧📖🌦️🌈
https://sites.ecmwf.int/docs/dev-section/fdb/pull-requests/PR-249

[codecov-commenter]

Codecov Report

❌ Patch coverage is 55.10204% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.14%. Comparing base (ef36e0f) to head (6401089).

Files with missing lines	Patch %	Lines
src/fdb5/toc/TocHandler.cc	55.10%	22 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #249      +/-   ##
===========================================
- Coverage    71.22%   71.14%   -0.08%     
===========================================
  Files          376      376              
  Lines        23762    23787      +25     
  Branches      2478     2484       +6     
===========================================
- Hits         16924    16923       -1     
- Misses        6838     6864      +26     

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[Ozaq]

@claude[agent] Review

[Claude]

@Ozaq I've opened a new pull request, #252, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

Pull request overview

This PR updates the SubToc preloading path in TocHandler to improve robustness around AIO reads by adding timeout-based aio_suspend() handling, additional debug logging, and cleanup-on-exception behavior.

Changes:

• Add a 1s timeout to aio_suspend() and log when reads appear stalled before retrying.
• Add RAII cancellation/reaping for outstanding AIO requests during stack unwinding.
• Update Python test CMake environments to further isolate against globally installed libraries via FINDLIBS_DISABLE_PACKAGE.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/fdb5/toc/TocHandler.cc	Adds AIO timeout/retry logging and introduces cleanup logic for AIO requests during errors.
tests/pyfdb/CMakeLists.txt	Extends test environment variables to disable package-based library discovery.

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[Ozaq]

@claude review

[Copilot]

Pull request overview

This PR improves robustness/observability of asynchronous SubToc preloading by adding timeout-based stall logging and attempting to ensure AIO requests are cancelled/cleaned up on exceptions, and it adjusts Python test environments to avoid accidentally picking up globally installed dependencies.

Changes:

• Add a 1s aio_suspend() timeout loop that logs stalled SubToc reads and retries.
• Add RAII cleanup for file descriptors and AIO requests during stack unwinding.
• Update tests/pyfdb CMake test environment to disable package-based findlibs resolution.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
tests/pyfdb/CMakeLists.txt	Adds FINDLIBS_DISABLE_PACKAGE=yes to test environments to avoid using globally installed packages/libs.
src/fdb5/toc/TocHandler.cc	Enhances SubToc AIO preload logic with timeout logging and introduces RAII cancellation/reaping on exceptions.

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