With the introduction of the $collStats aggregation stage, users have the ability to obtain result based on read preference. 

However, it is important for tools like mongosync to have the ability to get $collStats for each node since the index metadata could be different. Because $collStats is not querying each node, mongosync could not fully validate that there is no corrupted index for each node. 

Add a new flag called targetAllNodes to $collStats which, if set, stipulates that it should target every data-bearing member in each shard and return an exhaustive list of results from all nodes in the cluster. 

Ideally, it would do similar work as the targetAllNodes option for $curentOp described in SERVER-34633.