Currently a member with a lower machine version will never vote for a member with a higher machine version. This is to avoid a higher versioned member being elected before there is a quorum of higher versioned members. This is somewhat too restrictive in the edge case where there already is a quorum of higher versioned members but the quorum is lost.
Say if node A (leader) and B run version 2 and node C run version 1 and A is terminated currently neither B nor C can be elected leader. To allow C to vote for B we could allow this if the effective machine version known by C matches the machine version of B.
To do so we can add a clause for this in the ra_server:process_pre_vote function to allow this specific case.
Currently a member with a lower machine version will never vote for a member with a higher machine version. This is to avoid a higher versioned member being elected before there is a quorum of higher versioned members. This is somewhat too restrictive in the edge case where there already is a quorum of higher versioned members but the quorum is lost.
Say if node A (leader) and B run version 2 and node C run version 1 and A is terminated currently neither B nor C can be elected leader. To allow C to vote for B we could allow this if the effective machine version known by C matches the machine version of B.
To do so we can add a clause for this in the
ra_server:process_pre_votefunction to allow this specific case.