Fix race in ScanIteratorBase.Dispose causing intermittent ObjectDisposedException#1667
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Two changes to Dispose(): 1. Move 'loadCompletionEvents = default' from inside the per-frame loop to after the loop. With frameSize=2, the old code nulled the entire array on the first iteration (i=0), causing iteration i=1 to skip waiting for its in-flight async read. The read callback (AsyncReadPageWithObjectsCallback) would then access the already-disposed CircularDiskReadBuffer, crashing the test host with an unhandled ObjectDisposedException. 2. Separate the Wait (which can throw on cancellation) from resource cleanup. The event, CTS, and read buffer disposals now run unconditionally after the try/catch, ensuring resources are always cleaned up even when the wait fails. Co-authored-by: Copilot <[email protected]>
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Pull request overview
This PR fixes an intermittent ObjectDisposedException during disk-scan iterator teardown by ensuring all per-frame async page-load completion events are awaited and disposed correctly (especially important under double-page buffering).
Changes:
- Refactors
ScanIteratorBase.Dispose()to wait on each frame’sloadCompletionEvents[i]before disposing associated resources. - Moves
loadCompletionEvents = defaultto after the per-frame loop to avoid prematurely nulling the array. - Ensures completion events, cancellation token sources, and read buffers are disposed even if the wait throws.
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Fixes an intermittent test host crash (ObjectDisposedException: Cannot access a disposed object. Object name: 'CircularDiskReadBuffer') observed in CI during InsDelIns_LocalMemory.
Root cause: In ScanIteratorBase.Dispose(), loadCompletionEvents = default was inside the per-frame loop, nulling the entire array after processing frame 0. With DoublePageBuffering (frameSize=2), frame 1's completion event was never waited on, so its CircularDiskReadBuffer was disposed while AsyncReadPageWithObjectsCallback was still using it on a thread pool thread.
Fix: Move loadCompletionEvents = default from inside the loop to after the loop, ensuring all frames are properly awaited before their read buffers are disposed.