Operational Defect Database
BugZero found this defect 129 days ago.
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MongoDB | 2543519
Resharding remainingOpTime algorithm doesn't work with low elapsedTime
Last update date:
3/13/2024
Affected products:
MongoDB Server
Affected releases:
5.0.0
6.0.0
7.0.0
7.2.0
Fixed releases:
No fixed releases provided.
Description:
Info
In the following algorithm for calculating remainingTime to complete for resharding op, used by resharding commit monitor: Milliseconds remainingTime(Milliseconds elapsedTime, double elapsedWork, double totalWork) { elapsedWork = std::min(elapsedWork, totalWork); double remainingMsec = 1.0 * elapsedTime.count() * (totalWork / elapsedWork - 1); return Milliseconds(Milliseconds::rep(remainingMsec)); } If the elapsedTime is of the order of few ms, the remainingMsec can be incorrectly reported. For example in the HELP-54235, with ~300k fetched oplog entries (totalWork) and a 1000 applied oplog entries (elapsedWork) and a value of elapsedTime as 6ms will result in engaging the CS as: remainingMsec = 1.0 * 6 * (300-1) ≈ 1800 ms = 1.8 seconds This algorithm needs to change to handle this edge case.
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