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    Type:Improvement 
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    Resolution: Works as Designed
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    Priority:Major - P3 
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    None
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    Affects Version/s: 4.0.14
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    Component/s: Replication
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    None
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        Fully Compatible
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        (copied to CRM)
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        None
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        None
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        None
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        None
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During an initial sync we can fail to clone a collection from the sync source. The messages logged are as follows.
YYYY-MM-DDTHH:MM:SSZ I REPL [repl writer worker 1] Finished cloning data: InitialSyncFailure: Failed to clone 1 collection(s) in 'DBNAME' from HOST:PORT. Beginning oplog replay.
To improve diagnostics it would be a good idea to log the collection name that failed.