What means this Log Message - "ctx": "ReplCoordExtern-0", "msg": "Recreating cursor for oplog fetcher due to error"

I checked this log message while looking at the log message.

{“t”: {"$date": “2021-12-01T16:53:40.190+09:00”}, “s”: “I”, “c”: “REPL”, “id”: 21275, “ctx”: “ReplCoordExtern-0”, “msg”: “Recreating cursor for oplog fetcher due to error”, “attr”: {“lastOpTimeFetched”: {“ts”: {"$timestamp": {“t”: 1638342675, “i”: 13} }, “attemptsRemaining”: 1, “error”: “CursorNotFound: Error while getting the next batch in the oplog fetcher :: caused by :: cursor id 5487530264003139393 not found”} }

Although it is “I”, I want to know the meaning of the log message.
This log message came from the secondary that gave the slaveDelay option.

What is “Oplog Fetcher”?
And what kind of work does this do?

Hi @Kim_Hakseon ,

Oplog fetcher is a process that fetches oplogs from a source replicating server (usually primary).

So it make sense it is present on any secondary. From time to time it might fail due to timeouts or closed cursors on the primary and it will restart from the last successful point.

Therefore this should not indicate on any immediate problem. However if it happens often it should be investigated…


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Thank you so much for your answer.

Additionally, when a secondary to which the slaveDelay option is applied fetches the primary’s oplog, what is the timeout that occurs?

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