Currently, resharding tracks metrics via ReshardingMetrics reported in $currentOp and ReshardingCumulativeMetrics (via its base class) reported in serverStatus. Because the serverStatus command returns metrics from the whole host in aggregate, it's difficult to capture metrics that are specific to a particular operation. As such, there are some metrics (e.g. duration spent in each phase) that are only reported by $currentOp. However, $currentOp is only available while the operation is still running, which limits its usefulness when trying to do analysis after the fact. Therefore, we should log the BSON object returned by reportForCurrentOp() at the end of the resharding operation.