Currently, we persist the 'commitQuorum' value that user provided for createIndexes cmd, into "config.system.IndexBuilds collection, only on receiving first ready to commit vote by primary. If current primary gets restarted/rolled back before receiving any votes, and gets re-elected, then new primary would not know about the commit quorum value. Currently, we crash our system. As, our current contract is, two phase index build should have a commit quorum value set.
To be noted, all the nodes who are eligible to become primary should have the commit quorum value, as the 2 phase index build can survive state transition and any node can act as coordinator for the 2 phase index build.