Brian is an administrator process for Borealis. It acts as a router for all messages in the system and it is responsible for controlling the flow of logic. This process was originally called Brain, but after repeated misspellings, the name Brian stuck.
Brian implements a ZMQ router in order for all the other processes to connect. Using a ZMQ router lets us to use a feature of ZMQ for named sockets. The premise of named sockets is that we can connect a single router address, and when we connect we can supply a name for the socket we are connecting from. ZMQ’s router process will then automatically know how to send data to that socket if another socket sends to the identity instead of an address. This makes following the flow of messages much easier to track. By having all messages flow through a router, its possible to log the flow of data between sockets to make sure that the pipeline of messages is occuring in the correct order, and if not it is a helpful tool in debugging.
Brian is also responsible for rate controlling the system. Since all the traffic routes through this module, it is an ideal place to make sure that the pipeline isn’t being overwhelmed by any modules. This step is very important to make sure that the GPU processing isn’t being overloaded with work or that too many new requests enter the USRP driver.