When clients find that they're failing a lot of circuits, they back off from their computed cbt value, which puts them in the "launch a bunch of test circuits so we can get a better estimate of our cbt" phase. By default they launch 100 circuits, one per circuit_build_times_test_frequency(), from circuit_build_needed_circs() which calls circuit_predict_and_launch_new() which does ``` if (num < MAX_UNUSED_OPEN_CIRCUITS-2 && get_options()->LearnCircuitBuildTimeout && circuit_build_times_needs_circuits_now(&circ_times)) { flags = CIRCLAUNCH_NEED_CAPACITY; log_info(LD_CIRC, "Have %d clean circs need another buildtime test circ.", num); circuit_launch(CIRCUIT_PURPOSE_C_GENERAL, flags); ``` I think while our network is overloaded (legacy/trac#9657), we should turn this behavior off. To do it, we need to set ``` cbtdisabled=1 cbtmincircs=1 ``` in our consensus params. (We need to set both because there's a bug where it doesn't look at cbtdisabled when making the decision. But I'll open that as a separate ticket.)