Often, when investigating HELP tickets related to balancing, we need to access and combine data from FTDC, logs and configdump to figure some basic metrics such as:

• Migration throughput (how fast is this shard cloning data)
• Range deleter throughout (how fast is this shard executing its range deletions)
• Number of orphans documents (how many orphans documents are waiting to be deleted)

The following statistics should be available on serverStatus under the shardingStatistics group (besides the currently already available):

• countDocsClonedOnCatchUpOnRecipient: the number of documents cloned during the catch up phase of the migration
• countBytesClonedOnCatchUpOnRecipient: the number of bytes cloned during the catch up phase of the migration
• countDonorMoveChunkCommitted: the total number of migrations committed by the node
• countDonorMoveChunkAborted: the number of migrations aborted in the node
• totalDonorMoveChunkTimeMillis: the total amount of time a migration took from beginning to end
• totalRecipientCriticalSectionTimeMillis: the amount of time in milliseconds the recipient of a migration spent holding the critical section