// 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 }
// doPhase2 performs classic paxos phase2 steps. func (this *Paxos) doPhase2(ctxHeader *msgpb.Header, ballot int64, value []byte, acceptorList []string) error { phase2request := thispb.Phase2Request{} phase2request.BallotNumber = proto.Int64(ballot) phase2request.ProposedValue = value message := thispb.PaxosMessage{} message.Phase2Request = &phase2request header := msg.NewNestedRequest(this.msn, ctxHeader, this.namespace, this.uid, "ClassicPaxos.Phase2") defer this.msn.CloseMessage(header) count, errSend := msg.SendAllProto(this.msn, acceptorList, header, &message) if errSend != nil && count < this.MajoritySize() { this.Errorf("could not send phase2 request to majority acceptors: %v", errSend) return errSend } this.Infof("send phase2 request %s to acceptors: %v", header, acceptorList) responseMap := make(map[string]*thispb.Phase2Response) for ii := 0; ii < count && len(responseMap) < this.MajoritySize(); ii++ { message := thispb.PaxosMessage{} resHeader, errRecv := msg.ReceiveProto(this.msn, header, &message) if errRecv != nil { break } acceptor := resHeader.GetMessengerId() if _, ok := responseMap[acceptor]; ok { this.Warningf("duplicate phase2 response from %s (ignored)", acceptor) continue } if message.Phase2Response == nil { this.Warningf("phase2 response data is empty from %s (ignored)", acceptor) continue } response := message.GetPhase2Response() promisedBallot := response.GetPromisedBallot() if promisedBallot < ballot { this.Errorf("as per phase2 response, acceptor %s seems to have rolled "+ "back on his phase1 promise to ballot %d", acceptor, ballot) continue } if promisedBallot > ballot { this.Warningf("acceptor %s has moved on to higher ballot %d", acceptor, promisedBallot) break } responseMap[acceptor] = response } if len(responseMap) < this.MajoritySize() { this.Warningf("could not get majority phase2 votes %v for value [%s] "+ "ballot %d", responseMap, value, ballot) return errs.ErrRetry } this.Infof("value [%s] is chosen by phase2 responses %v", value, responseMap) return nil }