// ElectLeader performs a leader election for the next round.
func (this *Election) ElectLeader(timeout time.Duration) (
string, int64, error) {
lock := this.ctlr.ReadLockAll()
target := this.msn.UID()
if !this.InCommittee() {
target = this.committee[rand.Intn(len(this.committee))]
}
lock.Unlock()
request := thispb.ElectRequest{}
request.ElectionRound = proto.Int64(this.CurrentRound() + 1)
message := thispb.ElectionMessage{}
message.ElectRequest = &request
reqHeader := this.msn.NewRequest(this.namespace, this.uid, "Election.Elect",
timeout)
defer this.msn.CloseMessage(reqHeader)
if err := msg.SendProto(this.msn, target, reqHeader, &message); err != nil {
this.Errorf("could not send elect request to %s: %v", target, err)
return "", -1, err
}
message.Reset()
_, errRecv := msg.ReceiveProto(this.msn, reqHeader, &message)
if errRecv != nil {
this.Errorf("could not receive elect response from %s: %v", target,
errRecv)
return "", -1, errRecv
}
if message.ElectResponse == nil {
this.Errorf("elect response from %s is empty", target)
return "", -1, errs.ErrCorrupt
}
response := message.GetElectResponse()
change := thispb.ElectionChange{}
change.ElectionRound = response.ElectionRound
change.ElectionWinner = response.ElectionWinner
if err := this.UpdateElection(&change); err != nil {
this.Errorf("could not update to new election round: %v", err)
return "", -1, err
}
newRound := response.GetElectionRound()
newLeader := response.GetElectionWinner()
return newLeader, newRound, nil
}
// Propose proposes given value for a consensus.
//
// value: The value to propose for consensus.
//
// timeout: Maximum time duration for the propose operation.
//
// Returns the chosen value on success.
func (this *Paxos) Propose(value []byte, timeout time.Duration) (
[]byte, error) {
// If local instance is not a proposer, find a random proposer.
proposer := this.msn.UID()
if !this.IsProposer() {
proposer = this.proposerList[rand.Intn(len(this.proposerList))]
this.Infof("using %s as the proposer", proposer)
}
// Send the propose request.
request := thispb.ProposeRequest{}
request.ProposedValue = value
message := thispb.PaxosMessage{}
message.ProposeRequest = &request
reqHeader := this.msn.NewRequest(this.namespace, this.uid,
"ClassicPaxos.Propose", timeout)
errSend := msg.SendProto(this.msn, proposer, reqHeader, &message)
if errSend != nil {
this.Errorf("could not send propose request to %s: %v", proposer, errSend)
return nil, errSend
}
// Wait for the response.
_, errRecv := msg.ReceiveProto(this.msn, reqHeader, &message)
if errRecv != nil {
this.Errorf("could not receive propose response from %s: %v", proposer,
errRecv)
return nil, errRecv
}
if message.ProposeResponse == nil {
this.Errorf("propose response from %s is empty", proposer)
return nil, errs.ErrCorrupt
}
response := message.GetProposeResponse()
return response.GetChosenValue(), nil
}