Very important for us feature, to identify client processes, appname is not avaible while connecting over sharded cluster environment (e.g over mongos). appname only appear in log file, prodused by mongos.
If we connect named client to mongod directly - then currentOp show appname of the client:

2017-03-29T15:16:54.381+0700 I NETWORK  [conn1] received client metadata from 127.0.0.1:38611 conn1: { application: { *name: "MongoDB Shell"* }, driver: { name: "MongoDB Internal Client", version: ...

via client_metadata.cpp

   log() << "received client metadata from " << client->getRemote().toString() << " "
          << client->desc() << ": " << getDocument();

My question is how to patch mongo (mongos) sources, so this information be avaible in currentOp output - while caller of currentOp - connects over mongos. (I'm will be propose this behaviour avaible in general release, but now its important for us).