SERVER-35639 added the port to the hostname in changelog entries. However, if the replset membership of shards is changing frequently, it can still be hard to match up this host:port with the corresponding shard, eg. if a config dump from the appropriate time is not available (since the entries in config.shards are not versioned). Therefore, it would be useful if changelog entries also included an optional field which is the name of the shard performing the operation (for operations on shards), "config" for operations on configsvrs, and absent for operations on mongos.