The mongos fsync with lock command should ensure that there are no DDL operations in progress on any shard. The fsync with lock command must first lock the shard and then verify if any DDL operations are in progress (this ordering of operations, inhibits any new DDL operation from starting before locking the shard). If any in-progress DDL operations are detected on any shard, the mongos fsync with lock command must fail, unlock any locked shards and return an appropriate error to the user.
Determine if an additional parameter (to detect DDL operations in progress) must be passed while broadcasting the fsync with lock command to all shards.
This capability will only be available in v6.0 and above.