We currently document a serverStatus field shardingStatistics.resharding.totalOperationTimeElapsedMillis, however this field was never actually reported by the old metrics implementation as of 6.0 and is also not reported by the new implementation which we started using in 6.1.

The oldest running resharding operation's elapsed time in milliseconds should be reported in the output of serverStatus as shardingStatistics.resharding.oldestActive.totalOperationTimeElapsedMillis.

Consider also adding a counter for the elapsed time for the most recent successful operation, to ease tracking resharding performance in atlas based on historical serverStatus data.