Compressor 2 can accelerate processing by distributing the work to multiple computers. If you're using an Apple QMaster cluster for distributed processing, a user must be logged in to each Compressor service node (a computer providing Compressor-distributed processing services) for full functionality. If a service node displays the login screen, that computer will be bypassed in the processing distribution.
For more information on distributed processing, open Compressor and choose Help > Distributed Processing Setup.