Merge pull request #600 from nspcc-dev/feature/smart_proposal

consensus: try to use previous proposal after ChangeView

Closes #591.

pkg/consensus/consensus.go

@@ -55,6 +55,7 @@ type service struct {
 	// everything in single thread.
 	messages     chan Payload
 	transactions chan *transaction.Transaction
+	lastProposal []util.Uint256
 }
 
 // Config is a configuration for consensus services.
@@ -205,7 +206,9 @@ func (s *service) OnPayload(cp *Payload) {
 	// we use switch here because other payloads could be possibly added in future
 	switch cp.Type() {
 	case payload.PrepareRequestType:
-		s.txx.Add(&cp.GetPrepareRequest().(*prepareRequest).minerTx)
+		req := cp.GetPrepareRequest().(*prepareRequest)
+		s.txx.Add(&req.minerTx)
+		s.lastProposal = req.transactionHashes
 	}
 
 	s.messages <- *cp
@@ -328,7 +331,23 @@ func (s *service) getBlock(h util.Uint256) block.Block {
 
 func (s *service) getVerifiedTx(count int) []block.Transaction {
 	pool := s.Config.Chain.GetMemPool()
-	txx := pool.GetVerifiedTransactions()
+
+	var txx []*transaction.Transaction
+
+	if s.dbft.ViewNumber > 0 {
+		txx = make([]*transaction.Transaction, 0, len(s.lastProposal))
+		for i := range s.lastProposal {
+			if tx, ok := pool.TryGetValue(s.lastProposal[i]); ok {
+				txx = append(txx, tx)
+			}
+		}
+
+		if len(txx) < len(s.lastProposal)/2 {
+			txx = pool.GetVerifiedTransactions()
+		}
+	} else {
+		txx = pool.GetVerifiedTransactions()
+	}
 
 	res := make([]block.Transaction, len(txx)+1)
 	for i := range txx {

pkg/consensus/consensus_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/CityOfZion/neo-go/pkg/core/transaction"
 	"github.com/CityOfZion/neo-go/pkg/util"
 	"github.com/nspcc-dev/dbft/block"
+	"github.com/nspcc-dev/dbft/payload"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/zap/zaptest"
 )
@@ -28,6 +29,53 @@ func TestNewService(t *testing.T) {
 	require.Equal(t, tx, txx[1])
 }
 
+func TestService_GetVerified(t *testing.T) {
+	srv := newTestService(t)
+	txs := []*transaction.Transaction{
+		newMinerTx(1),
+		newMinerTx(2),
+		newMinerTx(3),
+		newMinerTx(4),
+	}
+	pool := srv.Chain.GetMemPool()
+	item := core.NewPoolItem(txs[3], new(feer))
+
+	require.True(t, pool.TryAdd(txs[3].Hash(), item))
+
+	hashes := []util.Uint256{txs[0].Hash(), txs[1].Hash(), txs[2].Hash()}
+
+	p := new(Payload)
+	p.SetType(payload.PrepareRequestType)
+	p.SetPayload(&prepareRequest{transactionHashes: hashes})
+	p.SetValidatorIndex(1)
+
+	priv, _ := getTestValidator(1)
+	require.NoError(t, p.Sign(priv))
+
+	srv.OnPayload(p)
+	require.Equal(t, hashes, srv.lastProposal)
+
+	srv.dbft.ViewNumber = 1
+
+	t.Run("new transactions will be proposed in case of failure", func(t *testing.T) {
+		txx := srv.getVerifiedTx(10)
+		require.Equal(t, 2, len(txx), "there is only 1 tx in mempool")
+		require.Equal(t, txs[3], txx[1])
+	})
+
+	t.Run("more than half of the last proposal will be reused", func(t *testing.T) {
+		for _, tx := range txs[:2] {
+			item := core.NewPoolItem(tx, new(feer))
+			require.True(t, pool.TryAdd(tx.Hash(), item))
+		}
+
+		txx := srv.getVerifiedTx(10)
+		require.Contains(t, txx, txs[0])
+		require.Contains(t, txx, txs[1])
+		require.NotContains(t, txx, txs[2])
+	})
+}
+
 func TestService_ValidatePayload(t *testing.T) {
 	srv := newTestService(t)
 	priv, _ := getTestValidator(1)