consensus: calculate prevote message delay metric

internal/consensus/metrics.go

@@ -64,6 +64,21 @@ type Metrics struct {
 
 	// Histogram of time taken per step annotated with reason that the step proceeded.
 	StepTime metrics.Histogram
+
+	// QuroumPrevoteMessageDelay is the difference in seconds between the proposal
+	// timestamp and the timestamp of the prevote that achieved a quorum in the prevote step.
+	// The prevote that achieved a quorum in the prevote step is determined by first
+	// sorting all of the collected prevotes in a round in ascending order of
+	// timestamp and iterating over this list from lowest timestamp to highest.
+	// During iteration, the total represented by iterated prevotes is kept track of.
+	// The prevote that achieved a quorum is the prevote that brings the summed
+	// voting power in this iteration to above 2/3 of the power on the network.
+	QuorumPrevoteMessageDelay metrics.Gauge
+
+	// FullPrevoteMessageDelay is the difference in seconds between the proposal
+	// timestamp and the timestamp of the prevote that achieved 100% of the voting
+	// power on the network in the prevote step when prevotes are ordered by timestamp.
+	FullPrevoteMessageDelay metrics.Gauge
 }
 
 // PrometheusMetrics returns Metrics build using Prometheus client library.
@@ -196,6 +211,20 @@ func PrometheusMetrics(namespace string, labelsAndValues ...string) *Metrics {
 			Name:      "step_time",
 			Help:      "Time spent per step.",
 		}, append(labels, "step", "reason")).With(labelsAndValues...),
+		QuorumPrevoteMessageDelay: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
+			Namespace: namespace,
+			Subsystem: MetricsSubsystem,
+			Name:      "quorum_prevote_message_delay",
+			Help: "Difference in seconds between the proposal timestamp and the timestamp " +
+				"of the prevote that achieved a quorum in the prevote step.",
+		}, labels).With(labelsAndValues...),
+		FullPrevoteMessageDelay: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
+			Namespace: namespace,
+			Subsystem: MetricsSubsystem,
+			Name:      "complete_prevote_message_delay",
+			Help: "Difference in seconds between the proposal timestamp and the timestamp " +
+				"of the prevote that achieved 100% of the voting power in the prevote step.",
+		}, labels).With(labelsAndValues...),
 	}
 }
 

internal/consensus/state.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"os"
 	"runtime/debug"
+	"sort"
 	"sync"
 	"time"
 
@@ -1680,6 +1681,8 @@ func (cs *State) finalizeCommit(ctx context.Context, height int64) {
 		return
 	}
 
+	cs.calculatePrevoteMessageDelayMetrics()
+
 	blockID, ok := cs.Votes.Precommits(cs.CommitRound).TwoThirdsMajority()
 	block, blockParts := cs.ProposalBlock, cs.ProposalBlockParts
 
@@ -2414,6 +2417,26 @@ func (cs *State) checkDoubleSigningRisk(height int64) error {
 	return nil
 }
 
+func (cs *State) calculatePrevoteMessageDelayMetrics() {
+	ps := cs.Votes.Prevotes(cs.Round)
+	pl := ps.List()
+	sort.Slice(pl, func(i, j int) bool {
+		return pl[i].Timestamp.Before(pl[j].Timestamp)
+	})
+	var votingPowerSeen int64
+	for _, v := range pl {
+		_, val := cs.Validators.GetByAddress(v.ValidatorAddress)
+		votingPowerSeen += val.VotingPower
+		if votingPowerSeen >= cs.Validators.TotalVotingPower()*(2/3+1) {
+			cs.metrics.QuorumPrevoteMessageDelay.Set(v.Timestamp.Sub(cs.Proposal.Timestamp).Seconds())
+			break
+		}
+	}
+	if ps.HasAll() {
+		cs.metrics.FullPrevoteMessageDelay.Set(pl[len(pl)-1].Timestamp.Sub(cs.Proposal.Timestamp).Seconds())
+	}
+}
+
 //---------------------------------------------------------
 
 func CompareHRS(h1 int64, r1 int32, s1 cstypes.RoundStepType, h2 int64, r2 int32, s2 cstypes.RoundStepType) int {

types/vote_set.go

@@ -378,6 +378,15 @@ func (voteSet *VoteSet) GetByIndex(valIndex int32) *Vote {
 	return voteSet.votes[valIndex]
 }
 
+// List returns a copy of the list of votes stored by the VoteSet.
+func (voteSet *VoteSet) List() []Vote {
+	votes := make([]Vote, len(voteSet.votes))
+	for i := range voteSet.votes {
+		votes[i] = *voteSet.votes[i]
+	}
+	return votes
+}
+
 func (voteSet *VoteSet) GetByAddress(address []byte) *Vote {
 	if voteSet == nil {
 		return nil