Method handle_request_vote

nodedb-raft/src/node/rpc/request_vote.rs:18–71

Handle incoming RequestVote RPC. Learners and observers never grant votes: by definition they are not members of the voting set for this term, and granting a vote could let an incorrect quorum form.

(&mut self, req: &RequestVoteRequest)

    /// members of the voting set for this term, and granting a vote could
    /// let an incorrect quorum form.
    pub fn handle_request_vote(&mut self, req: &RequestVoteRequest) -> RequestVoteResponse {
        match self.role {
            NodeRole::Learner | NodeRole::Observer => {
                // Learners and observers never grant votes.
                return RequestVoteResponse {
                    term: self.hard_state.current_term,
                    vote_granted: false,
                };
            }
            NodeRole::Follower | NodeRole::Candidate | NodeRole::Leader => {}
        }

        if req.term > self.hard_state.current_term {
            self.become_follower(req.term);
        }

        if req.term < self.hard_state.current_term {
            return RequestVoteResponse {
                term: self.hard_state.current_term,
                vote_granted: false,
            };
        }

        let voted_for = self.hard_state.voted_for;
        let can_vote = voted_for == 0 || voted_for == req.candidate_id;

        let log_ok = req.last_log_term > self.log.last_term()
            || (req.last_log_term == self.log.last_term()
                && req.last_log_index >= self.log.last_index());

        if can_vote && log_ok {
            self.hard_state.voted_for = req.candidate_id;
            self.persist_hard_state();
            self.reset_election_timeout();

            debug!(
                node = self.config.node_id,
                group = self.config.group_id,
                candidate = req.candidate_id,
                term = req.term,
                "granted vote"
            );

            RequestVoteResponse {
                term: self.hard_state.current_term,
                vote_granted: true,
            }
        } else {
            RequestVoteResponse {
                term: self.hard_state.current_term,
                vote_granted: false,
            }
        }
    }

    /// Handle RequestVote response (candidate only).
    pub fn handle_request_vote_response(&mut self, peer: u64, resp: &RequestVoteResponse) {