// Phase2RPC handles ClassicPaxos.Phase2 rpc. func (this *Paxos) Phase2RPC(header *msgpb.Header, request *thispb.Phase2Request) (status error) { if !this.IsAcceptor() { this.Errorf("this paxos instance is not an acceptor; rejecting %s", header) return errs.ErrInvalid } lock, errLock := this.ctlr.TimedLock(msg.RequestTimeout(header), "acceptor") if errLock != nil { return errLock } defer lock.Unlock() clientID := header.GetMessengerId() respond := func() error { response := thispb.Phase2Response{} response.PromisedBallot = proto.Int64(this.promisedBallot) if this.votedBallot >= 0 { response.VotedBallot = proto.Int64(this.votedBallot) response.VotedValue = this.votedValue } message := thispb.PaxosMessage{} message.Phase2Response = &response errSend := msg.SendResponseProto(this.msn, header, &message) if errSend != nil { this.Errorf("could not send phase2 response to %s: %v", clientID, errSend) return errSend } return nil } ballot := request.GetBallotNumber() if ballot < this.promisedBallot { this.Warningf("phase2 request from %s is ignored due to stale ballot %d", clientID, ballot) return respond() } if ballot > this.promisedBallot { this.Errorf("phase2 request from client %s without acquiring a prior "+ "promise", clientID) return respond() } value := request.GetProposedValue() // Save the phase2 vote into the wal. change := thispb.AcceptorChange{} change.VotedBallot = proto.Int64(ballot) change.VotedValue = value if err := this.doUpdateAcceptor(&change); err != nil { this.Errorf("could not update acceptor state: %v", err) return err } this.Infof("this acceptor has voted for %d in ballot %s", ballot, value) if err := respond(); err != nil { return err } // Schedule a notification to all learners. _ = this.alarm.ScheduleAt(this.uid, time.Now(), this.NotifyAllLearners) return nil }