// 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 }
// doPhase1 performs classic paxos phase1 steps. func (this *Paxos) doPhase1(ctxHeader *msgpb.Header, ballot int64, phase1AcceptorList []string) ([]byte, []string, error) { phase1request := thispb.Phase1Request{} phase1request.BallotNumber = proto.Int64(ballot) message := thispb.PaxosMessage{} message.Phase1Request = &phase1request reqHeader := msg.NewNestedRequest(this.msn, ctxHeader, this.namespace, this.uid, "ClassicPaxos.Phase1") defer this.msn.CloseMessage(reqHeader) count, errSend := msg.SendAllProto(this.msn, phase1AcceptorList, reqHeader, &message) if errSend != nil && count < this.MajoritySize() { this.Errorf("could not send phase1 request to majority nodes: %v", errSend) return nil, nil, errSend } this.Infof("sent phase1 request %s to acceptors %v", reqHeader, phase1AcceptorList) var acceptorList []string maxVotedBallot := int64(-1) var maxVotedValue []byte responseMap := make(map[string]*thispb.Phase1Response) for ii := 0; ii < count && len(responseMap) < this.MajoritySize(); ii++ { message := thispb.PaxosMessage{} resHeader, errRecv := msg.ReceiveProto(this.msn, reqHeader, &message) if errRecv != nil { this.Warningf("could not receive more phase1 responses for %s: %v", reqHeader, errRecv) break } acceptor := resHeader.GetMessengerId() if _, ok := responseMap[acceptor]; ok { this.Warningf("duplicate phase1 response from %s (ignored)", acceptor) continue } if message.Phase1Response == nil { this.Warningf("phase1 response data is empty from %s (ignored)", acceptor) continue } response := message.GetPhase1Response() if response.PromisedBallot == nil { this.Warningf("phase1 response from %s has no promise ballot", acceptor) continue } promisedBallot := response.GetPromisedBallot() if promisedBallot > ballot { this.Warningf("acceptor %s has moved on to ballot %d", acceptor, promisedBallot) break } if promisedBallot < ballot { this.Errorf("acceptor %s did not promise this ballot %d", acceptor, ballot) continue } // We received a promise from this acceptor. acceptorList = append(acceptorList, acceptor) responseMap[acceptor] = response // If there was a voted value already, we need to pick the max voted value. if response.VotedBallot != nil { votedBallot := response.GetVotedBallot() if votedBallot > maxVotedBallot { maxVotedBallot = votedBallot maxVotedValue = response.GetVotedValue() } } } if len(responseMap) < this.MajoritySize() { this.Warningf("could not get majority phase1 votes %v for ballot %d", responseMap, ballot) return nil, nil, errs.ErrRetry } if maxVotedValue == nil { this.Infof("no prior value was chosen as per phase1 responses %v", responseMap) } else { this.Infof("value [%s] could have been chosen as per phase1 responses %v", maxVotedValue, responseMap) } return maxVotedValue, acceptorList, nil }