Esempio n. 1
0
File: paxos.go Progetto: bvk/ascent
// NotifyAllLearners sends the current vote to all learners.
func (this *Paxos) NotifyAllLearners() (status error) {
	if !this.IsConfigured() || !this.IsAcceptor() {
		return nil
	}

	defer func() {
		if status != nil && !errs.IsClosed(status) {
			now := time.Now()
			next := now.Add(this.opts.LearnRetryInterval)
			_ = this.alarm.ScheduleAt(this.uid, next, this.NotifyAllLearners)
		}
	}()

	rlock := this.ctlr.ReadLock("acceptor", "config")
	// Stop notifications when all learners know the consensus value.
	if len(this.doneLearnerSet) == len(this.learnerList) {
		rlock.Unlock()
		return nil
	}
	// Make a copy of what we need: learners and the vote map.
	numLearners := len(this.learnerList)
	learnerList := append([]string{}, this.learnerList...)
	votedValueMap := make(map[int64][]byte)
	for ballot, value := range this.votedValueMap {
		if ackMap := this.learnerAckMap[ballot]; len(ackMap) < numLearners {
			votedValueMap[ballot] = value
		}
	}
	rlock.Unlock()

	request := thispb.LearnRequest{}
	for ballot, value := range votedValueMap {
		request.VotedBallotList = append(request.VotedBallotList, ballot)
		request.VotedValueList = append(request.VotedValueList, value)
	}
	message := thispb.PaxosMessage{}
	message.LearnRequest = &request

	// Send notification to all learners.
	reqHeader := this.msn.NewRequest(this.namespace, this.uid,
		"ClassicPaxos.Learn", this.opts.LearnTimeout)
	defer this.msn.CloseMessage(reqHeader)

	count, errSend := msg.SendAllProto(this.msn, learnerList, reqHeader,
		&message)
	if errSend != nil {
		this.Errorf("could not send learn request to all learners: %v", errSend)
		return errSend
	}

	// Wait for responses from all learners.
	for ii := 0; ii < count; ii++ {
		message := thispb.PaxosMessage{}
		resHeader, errRecv := msg.ReceiveProto(this.msn, reqHeader, &message)
		if errRecv != nil {
			this.Warningf("could not receive learner responses: %v", errRecv)
			break
		}

		learner := resHeader.GetMessengerId()
		if message.LearnResponse == nil {
			continue
		}
		response := message.GetLearnResponse()

		// Save the learner acknowledgment to the wal.
		change := thispb.AcceptorChange{}
		change.AckedLearner = proto.String(learner)
		if response.GetKnowsChosenValue() {
			change.AckedChosenValue = proto.Bool(true)
		} else {
			for ballot := range votedValueMap {
				change.AckedBallotList = append(change.AckedBallotList, ballot)
			}
		}
		if err := this.UpdateAcceptor(&change); err != nil {
			this.Errorf("could not update acceptor state: %v", err)
			return err
		}
	}
	return nil
}
Esempio n. 2
0
File: paxos.go Progetto: bvk/ascent
// 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
}
Esempio n. 3
0
File: paxos.go Progetto: bvk/ascent
// 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
}
Esempio n. 4
0
// 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
}