Operational Defect Database
BugZero found this defect 25 days ago.
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MongoDB | 2652720
BlockingResultsMerger doesn't yield session when disposing cursors
Last update date:
4/25/2024
Affected products:
MongoDB Server
Affected releases:
No affected releases provided.
Fixed releases:
No fixed releases provided.
Description:
Info
Suppose the following scenario: Operation A runs an aggregation on shard S1 with an AsyncResultsMerger of cursors C1 on S1, C2 on S2. Operation A then sends a getMore to S1 (itself) for C1 Operation A subsequently fails and attempts to dispose the cursors by sending a killCursors command to S1, and S2 for their cursors. The getMore sent previously (C1 on S1) gets executed as Operation B Operation A now waits so that all outstanding requests fail their cursors. This will deadlock the server in a multi-document transaction since waiting for the kills to take place will not yield the session. As a result Operation A will have the session checked out, which is required by Operation B, which in turn is required by Operation A to finish and yield the session.
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