When running a $currentOp agg with idleCursors: true, the host field for output documents with type: "idleCursor" doesn't include the port — but it should, like the type: "op" documents. Without this it's impossible to distinguish between multiple mongod/mongos servers running on different ports of a host.

It uses getHostNameCached() but should use getHostNameCachedAndPort() instead (see also $collStats).