Address PR review feedback from @champtar about the OCI chart caching
mechanism. The previous implementation used a 60-second timeout which
was arbitrary and caused race conditions when helm deployments took
longer (e.g., deployments triggering scaling up/down).
Changes:
- Replace 60s refresh marker timeout with proper reader-writer locks
- Use shared locks (RLock) when using cached charts (allows concurrent reads)
- Use exclusive locks (Lock) when refreshing/downloading charts
- Hold locks during entire helm operation lifecycle (not just during download)
- Add getNamedRWMutex() for in-process RW coordination
- Update PrepareCharts() to return locks map for lifecycle management
- Add chartLockReleaser in run.go to release locks after helm callback
- Remove unused mutexMap and getNamedMutex (replaced by RW versions)
- Add comprehensive tests for shared/exclusive lock behavior
This eliminates the race condition where one process could delete a
cached chart while another process's helm command was still using it.
Fixes review comment on PR #2298
Signed-off-by: Aditya Menon <amenon@canarytechnologies.com>
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