// 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
}
