Currently, ~~a relay is measured to~~ when measuring a relay, circuits are attempted to be built a maximum of 3 consecutives times when the previous ~~measurements fail~~ attempt fails, but in most of the cases, when ~~measuring a relay~~ building a circuit fails the first time, it will also fail the consecutives times. The relay will be measured anyway in the next iteration. Based on what we talked in https://trac.torproject.org/projects/tor/wiki/org/meetings/2019BrusselsNetworkTeam/Notes/SBWSRoadmap#Questions Edit: the three attempts happen when trying to build the circuit when measuring a relay, but it's not three attempts to measure the relay.