// RefreshLeader queries committee members for the latest election information.
func (this *Election) RefreshLeader(timeout time.Duration) (
string, int64, error) {
lock := this.ctlr.ReadLock("config")
committee := append([]string{}, this.committee...)
lock.Unlock()
request := thispb.StatusRequest{}
message := thispb.ElectionMessage{}
message.StatusRequest = &request
reqHeader := this.msn.NewRequest(this.namespace, this.uid, "Election.Status",
timeout)
defer this.msn.CloseMessage(reqHeader)
count, errSend := msg.SendAllProto(this.msn, committee, reqHeader, &message)
if errSend != nil && count < this.MajoritySize() {
this.Errorf("could not send status request to committee: %v", errSend)
return "", -1, errSend
}
// Wait for majority number of status responses and pick the winner for the
// largest election round. It may also happen that no election round exists
// because this instance is just created.
maxElectionRound := int64(-1)
maxElectionWinner := ""
remoteSet := make(map[string]struct{})
for ii := 0; ii < count && len(remoteSet) < this.MajoritySize(); ii++ {
message := thispb.ElectionMessage{}
resHeader, errRecv := msg.ReceiveProto(this.msn, reqHeader, &message)
if errRecv != nil {
this.Warningf("could not receive any more status responses for %s: %v",
reqHeader, errRecv)
break
}
memberID := resHeader.GetMessengerId()
if _, ok := remoteSet[memberID]; ok {
this.Warningf("duplicate status response from %s (ignored)", memberID)
continue
}
// TODO Check the response header for errors.
if message.StatusResponse == nil {
this.Warningf("status response data is empty from %s (ignored)",
memberID)
continue
}
response := message.GetStatusResponse()
if response.ElectionRound != nil {
round := response.GetElectionRound()
if round > maxElectionRound {
maxElectionRound = round
maxElectionWinner = response.GetElectionWinner()
}
}
remoteSet[memberID] = struct{}{}
}
if len(remoteSet) < this.MajoritySize() {
this.Errorf("could not get majority responses %v in finding leader",
remoteSet)
return "", -1, errs.ErrRetry
}
if maxElectionRound > this.CurrentRound() {
change := thispb.ElectionChange{}
change.ElectionRound = proto.Int64(maxElectionRound)
change.ElectionWinner = proto.String(maxElectionWinner)
if err := this.UpdateElection(&change); err != nil {
this.Errorf("could not update election status: %v", err)
return maxElectionWinner, maxElectionRound, err
}
}
this.Infof("found %s as the last known leader in round %d",
maxElectionWinner, maxElectionRound)
return maxElectionWinner, maxElectionRound, nil
}
