[SERVER-52676] Hedged reads should ignore stale errors - MongoDB Jira

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Backwards Compatibility:
Fully Compatible
Operating System:
ALL
Backport Requested:

v4.4
Steps To Reproduce:
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An insert occurs and it's majority written, but haven't been replicated on one of the nodes

A count operation is performed

The fastest request is the one to the node that haven't replicate the insert yet

A StaleDB or StaleShardVersion error is thrown
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An insert occurs and it's majority written, but haven't been replicated on one of the nodes A count operation is performed The fastest request is the one to the node that haven't replicate the insert yet A StaleDB or StaleShardVersion error is thrown
Linked BF Score:
45

Imagine the following scenario with a sharded cluster with 1 router, and 1 shard with 3 nodes and hedged reads active:

An insert occurs and it's majority written, but haven't been replicated on one of the nodes
A count operation is performed
The fastest request is the one to the node that haven't replicate the insert yet
A StaleDB or StaleShardVersion error is thrown

The current code only ignores MaxTimeMSExpired errors so a stale error will make the operation fail.