Currently mongoS logs a warning "mongos collstats doesn't know about: $gleStats" when collstats is executed, because the code in "src/mongo/s/commands_public.cpp:1210" doesn't list that field.

Alternatively, we may want to restructure the code to eliminate the need of explicit listing of all mongoD response fields. mongoS should be only aware of those that need special handling, like indexsizes and number of documents.