consensus/bor: eliminate contract calls for current span

consensus/bor/bor.go

@@ -49,6 +49,11 @@ const (
 	inmemorySignatures = 4096 // Number of recent block signatures to keep in memory
 )
 
+const (
+	spanLength    = 6400 // Number of blocks in a span
+	zerothSpanEnd = 255  // End block of 0th span
+)
+
 // Bor protocol constants.
 var (
 	defaultSprintLength = map[string]uint64{
@@ -1094,39 +1099,44 @@ func (c *Bor) Close() error {
 	return nil
 }
 
-func (c *Bor) checkAndCommitSpan(
-	state *state.StateDB,
-	header *types.Header,
-	chain core.ChainContext,
-) error {
-	var ctx = context.Background()
-	headerNumber := header.Number.Uint64()
+// SpanIdAt returns the corresponding span id for the given block number.
+func SpanIdAt(blockNum uint64) uint64 {
+	if blockNum > zerothSpanEnd {
+		return 1 + (blockNum-zerothSpanEnd-1)/spanLength
+	}
+	return 0
+}
 
-	span, err := c.spanner.GetCurrentSpan(ctx, header.ParentHash)
-	if err != nil {
-		return err
+// SpanEndBlockNum returns the number of the last block in the given span.
+func SpanEndBlockNum(spanId uint64) uint64 {
+	if spanId > 0 {
+		return spanId*spanLength + zerothSpanEnd
 	}
+	return zerothSpanEnd
+}
+
+func (c *Bor) checkAndCommitSpan(state *state.StateDB, header *types.Header, chain core.ChainContext) error {
+	// Find the current span at parent block
+	headerNumber := header.Number.Uint64()
+	spanId := SpanIdAt(headerNumber)
+	sprintLength := c.config.CalculateSprint(headerNumber)
 
-	if c.needToCommitSpan(span, headerNumber) {
-		return c.FetchAndCommitSpan(ctx, span.ID+1, state, header, chain)
+	// Fetch the next span if required
+	if needToCommitSpan(spanId, headerNumber, sprintLength) {
+		return c.FetchAndCommitSpan(context.Background(), spanId+1, state, header, chain)
 	}
 
 	return nil
 }
 
-func (c *Bor) needToCommitSpan(currentSpan *span.Span, headerNumber uint64) bool {
-	// if span is nil
-	if currentSpan == nil {
-		return false
-	}
-
-	// check span is not set initially
-	if currentSpan.EndBlock == 0 {
+func needToCommitSpan(spanId, headerNumber, sprintLength uint64) bool {
+	// Find the end block of the given span
+	spanEndBlock := SpanEndBlockNum(spanId)
+	if spanId == 0 && headerNumber == sprintLength {
+		// when in span 0 we fetch the next span (span 1) at the beginning of sprint 2 (block 16)
 		return true
-	}
-
-	// if current block is first block of last sprint in current span
-	if currentSpan.EndBlock > c.config.CalculateSprint(headerNumber) && currentSpan.EndBlock-c.config.CalculateSprint(headerNumber)+1 == headerNumber {
+	} else if spanEndBlock-sprintLength+1 == headerNumber {
+		// for subsequent spans, we always fetch the next span at the beginning of the last sprint of current span
 		return true
 	}
 

consensus/bor/bor_test.go

@@ -2,6 +2,7 @@ package bor
 
 import (
 	"math/big"
+	"strconv"
 	"testing"
 
 	"github.com/holiman/uint256"
@@ -162,3 +163,36 @@ func TestEncodeSigHeaderJaipur(t *testing.T) {
 	hash = SealHash(h, &params.BorConfig{JaipurBlock: big.NewInt(10)})
 	require.Equal(t, hash, hashWithoutBaseFee)
 }
+
+func TestNeedToCommitSpan(t *testing.T) {
+	type test struct {
+		spanId       uint64
+		headerNumber uint64
+		want         bool
+	}
+
+	tests := []test{
+		{spanId: 0, headerNumber: 1, want: false},
+		{spanId: 0, headerNumber: 15, want: false},
+		{spanId: 0, headerNumber: 16, want: true}, // Second sprint start
+		{spanId: 0, headerNumber: 17, want: false},
+		{spanId: 1, headerNumber: 256, want: false},
+		{spanId: 1, headerNumber: 6639, want: false},
+		{spanId: 1, headerNumber: 6640, want: true}, // First block of last sprint of span 1
+		{spanId: 1, headerNumber: 6641, want: false},
+		{spanId: 1, headerNumber: 6655, want: false},
+		{spanId: 100, headerNumber: 633856, want: false},
+		{spanId: 100, headerNumber: 640239, want: false},
+		{spanId: 100, headerNumber: 640240, want: true}, // First block of last sprint of span 100
+		{spanId: 100, headerNumber: 640241, want: false},
+	}
+
+	for _, test := range tests {
+		test := test
+		name := "id=" + strconv.FormatUint(test.spanId, 10) + ",number=" + strconv.FormatUint(test.headerNumber, 10)
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+			require.Equal(t, test.want, needToCommitSpan(test.spanId, test.headerNumber, 16))
+		})
+	}
+}

consensus/bor/snapshot.go

@@ -147,6 +147,9 @@ func (s *Snapshot) apply(headers []*types.Header, c *Bor) (*Snapshot, error) {
 		// add recents
 		snap.Recents[number] = signer
 
+		// TODO
+		// Can't we do this step for the last header only?
+
 		// change validator set and change proposer
 		if number > 0 && (number+1)%s.chainConfig.Bor.CalculateSprint(number) == 0 {
 			if err := validateHeaderExtraField(header.Extra); err != nil {