We currently know when/how many times multiplanner ran and its exit conditions because there are counters for it. We'll need something similar for CBR, to be able to assess whether it is running or not. We initially just need a counter to know how many times it was ran. Candidate location here: https://github.com/10gen/mongo/blob/c451c03ca2078bbeb43a0671799fd783db1a133f/src/mongo/db/query/get_executor.cpp#L523