fix(baseapp): select txs correctly with no-op mempool

CHANGELOG.md

@@ -62,6 +62,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Bug Fixes
 
+* (baseapp) [#17769](https://github.com/cosmos/cosmos-sdk/pull/17769) Ensure we respect block size constraints in the `DefaultProposalHandler`'s `PrepareProposal` handler when a nil or no-op mempool is used. We provide a `TxSelector` type to assist in making transaction selection generalized. We also fix a comparison bug in tx selection when `req.maxTxBytes` is reached.
 * (types) [#16583](https://github.com/cosmos/cosmos-sdk/pull/16583), [#17372](https://github.com/cosmos/cosmos-sdk/pull/17372), [#17421](https://github.com/cosmos/cosmos-sdk/pull/17421), [#17713](https://github.com/cosmos/cosmos-sdk/pull/17713) Introduce `PreBlock`, which executes in `FinalizeBlock` before `BeginBlock`. It allows the application to modify consensus parameters and have access to VE state. Note, `PreFinalizeBlockHook` is replaced by`PreBlocker`.
 * (baseapp) [#17518](https://github.com/cosmos/cosmos-sdk/pull/17518) Utilizing voting power from vote extensions (CometBFT) instead of the current bonded tokens (x/staking) to determine if a set of vote extensions are valid.
 * (config) [#17649](https://github.com/cosmos/cosmos-sdk/pull/17649) Fix `mempool.max-txs` configuration is invalid in `app.config`.

baseapp/abci_utils.go

@@ -139,23 +139,32 @@ type (
 	ProposalTxVerifier interface {
 		PrepareProposalVerifyTx(tx sdk.Tx) ([]byte, error)
 		ProcessProposalVerifyTx(txBz []byte) (sdk.Tx, error)
+		TxDecode(txBz []byte) (sdk.Tx, error)
+		TxEncode(tx sdk.Tx) ([]byte, error)
 	}
 
 	// DefaultProposalHandler defines the default ABCI PrepareProposal and
 	// ProcessProposal handlers.
 	DefaultProposalHandler struct {
 		mempool    mempool.Mempool
 		txVerifier ProposalTxVerifier
+		txSelector TxSelector
 	}
 )
 
-func NewDefaultProposalHandler(mp mempool.Mempool, txVerifier ProposalTxVerifier) DefaultProposalHandler {
-	return DefaultProposalHandler{
+func NewDefaultProposalHandler(mp mempool.Mempool, txVerifier ProposalTxVerifier) *DefaultProposalHandler {
+	return &DefaultProposalHandler{
 		mempool:    mp,
 		txVerifier: txVerifier,
+		txSelector: NewDefaultTxSelector(),
 	}
 }
 
+// SetTxSelector sets the TxSelector function on the DefaultProposalHandler.
+func (h *DefaultProposalHandler) SetTxSelector(ts TxSelector) {
+	h.txSelector = ts
+}
+
 // PrepareProposalHandler returns the default implementation for processing an
 // ABCI proposal. The application's mempool is enumerated and all valid
 // transactions are added to the proposal. Transactions are valid if they:
@@ -176,77 +185,61 @@ func NewDefaultProposalHandler(mp mempool.Mempool, txVerifier ProposalTxVerifier
 // - If no mempool is set or if the mempool is a no-op mempool, the transactions
 // requested from CometBFT will simply be returned, which, by default, are in
 // FIFO order.
-func (h DefaultProposalHandler) PrepareProposalHandler() sdk.PrepareProposalHandler {
+func (h *DefaultProposalHandler) PrepareProposalHandler() sdk.PrepareProposalHandler {
 	return func(ctx sdk.Context, req *abci.RequestPrepareProposal) (*abci.ResponsePrepareProposal, error) {
+		var maxBlockGas uint64
+		if b := ctx.ConsensusParams().Block; b != nil {
+			maxBlockGas = uint64(b.MaxGas)
+		}
+
+		defer h.txSelector.Clear()
+
 		// If the mempool is nil or NoOp we simply return the transactions
 		// requested from CometBFT, which, by default, should be in FIFO order.
+		//
+		// Note, we still need to ensure the transactions returned respect req.MaxTxBytes.
 		_, isNoOp := h.mempool.(mempool.NoOpMempool)
 		if h.mempool == nil || isNoOp {
-			return &abci.ResponsePrepareProposal{Txs: req.Txs}, nil
-		}
+			for _, txBz := range req.Txs {
+				tx, err := h.txVerifier.TxDecode(txBz)
+				if err != nil {
+					return nil, err
+				}
 
-		var maxBlockGas int64
-		if b := ctx.ConsensusParams().Block; b != nil {
-			maxBlockGas = b.MaxGas
-		}
+				stop := h.txSelector.SelectTxForProposal(uint64(req.MaxTxBytes), maxBlockGas, tx, txBz)
+				if stop {
+					break
+				}
+			}
 
-		var (
-			selectedTxs  [][]byte
-			totalTxBytes int64
-			totalTxGas   uint64
-		)
+			return &abci.ResponsePrepareProposal{Txs: h.txSelector.SelectedTxs()}, nil
+		}
 
 		iterator := h.mempool.Select(ctx, req.Txs)
-
 		for iterator != nil {
 			memTx := iterator.Tx()
 
 			// NOTE: Since transaction verification was already executed in CheckTx,
 			// which calls mempool.Insert, in theory everything in the pool should be
 			// valid. But some mempool implementations may insert invalid txs, so we
 			// check again.
-			bz, err := h.txVerifier.PrepareProposalVerifyTx(memTx)
+			txBz, err := h.txVerifier.PrepareProposalVerifyTx(memTx)
 			if err != nil {
 				err := h.mempool.Remove(memTx)
 				if err != nil && !errors.Is(err, mempool.ErrTxNotFound) {
 					return nil, err
 				}
 			} else {
-				var txGasLimit uint64
-				txSize := int64(len(bz))
-
-				gasTx, ok := memTx.(GasTx)
-				if ok {
-					txGasLimit = gasTx.GetGas()
-				}
-
-				// only add the transaction to the proposal if we have enough capacity
-				if (txSize + totalTxBytes) < req.MaxTxBytes {
-					// If there is a max block gas limit, add the tx only if the limit has
-					// not been met.
-					if maxBlockGas > 0 {
-						if (txGasLimit + totalTxGas) <= uint64(maxBlockGas) {
-							totalTxGas += txGasLimit
-							totalTxBytes += txSize
-							selectedTxs = append(selectedTxs, bz)
-						}
-					} else {
-						totalTxBytes += txSize
-						selectedTxs = append(selectedTxs, bz)
-					}
-				}
-
-				// Check if we've reached capacity. If so, we cannot select any more
-				// transactions.
-				if totalTxBytes >= req.MaxTxBytes || (maxBlockGas > 0 && (totalTxGas >= uint64(maxBlockGas))) {
+				stop := h.txSelector.SelectTxForProposal(uint64(req.MaxTxBytes), maxBlockGas, memTx, txBz)
+				if stop {
 					break
 				}
 			}
 
 			iterator = iterator.Next()
 		}
 
-		return &abci.ResponsePrepareProposal{Txs: selectedTxs}, nil
+		return &abci.ResponsePrepareProposal{Txs: h.txSelector.SelectedTxs()}, nil
 	}
 }
 
@@ -261,7 +254,7 @@ func (h DefaultProposalHandler) PrepareProposalHandler() sdk.PrepareProposalHand
 // DefaultPrepareProposal. It is very important that the same validation logic
 // is used in both steps, and applications must ensure that this is the case in
 // non-default handlers.
-func (h DefaultProposalHandler) ProcessProposalHandler() sdk.ProcessProposalHandler {
+func (h *DefaultProposalHandler) ProcessProposalHandler() sdk.ProcessProposalHandler {
 	// If the mempool is nil or NoOp we simply return ACCEPT,
 	// because PrepareProposal may have included txs that could fail verification.
 	_, isNoOp := h.mempool.(mempool.NoOpMempool)
@@ -330,3 +323,73 @@ func NoOpVerifyVoteExtensionHandler() sdk.VerifyVoteExtensionHandler {
 		return &abci.ResponseVerifyVoteExtension{Status: abci.ResponseVerifyVoteExtension_ACCEPT}, nil
 	}
 }
+
+// TxSelector defines a helper type that assists in selecting transactions during
+// mempool transaction selection in PrepareProposal. It keeps track of the total
+// number of bytes and total gas of the selected transactions. It also keeps
+// track of the selected transactions themselves.
+type TxSelector interface {
+	// SelectedTxs should return a copy of the selected transactions.
+	SelectedTxs() [][]byte
+
+	// Clear should clear the TxSelector, nulling out all relevant fields.
+	Clear()
+
+	// SelectTxForProposal should attempt to select a transaction for inclusion in
+	// a proposal based on inclusion criteria defined by the TxSelector. It must
+	// return <true> if the caller should halt the transaction selection loop
+	// (typically over a mempool) or <false> otherwise.
+	SelectTxForProposal(maxTxBytes, maxBlockGas uint64, memTx sdk.Tx, txBz []byte) bool
+}
+
+type defaultTxSelector struct {
+	totalTxBytes uint64
+	totalTxGas   uint64
+	selectedTxs  [][]byte
+}
+
+func NewDefaultTxSelector() TxSelector {
+	return &defaultTxSelector{}
+}
+
+func (ts *defaultTxSelector) SelectedTxs() [][]byte {
+	txs := make([][]byte, len(ts.selectedTxs))
+	copy(txs, ts.selectedTxs)
+	return txs
+}
+
+func (ts *defaultTxSelector) Clear() {
+	ts.totalTxBytes = 0
+	ts.totalTxGas = 0
+	ts.selectedTxs = nil
+}
+
+func (ts *defaultTxSelector) SelectTxForProposal(maxTxBytes, maxBlockGas uint64, memTx sdk.Tx, txBz []byte) bool {
+	txSize := uint64(len(txBz))
+
+	var txGasLimit uint64
+	if memTx != nil {
+		if gasTx, ok := memTx.(GasTx); ok {
+			txGasLimit = gasTx.GetGas()
+		}
+	}
+
+	// only add the transaction to the proposal if we have enough capacity
+	if (txSize + ts.totalTxBytes) <= maxTxBytes {
+		// If there is a max block gas limit, add the tx only if the limit has
+		// not been met.
+		if maxBlockGas > 0 {
+			if (txGasLimit + ts.totalTxGas) <= maxBlockGas {
+				ts.totalTxGas += txGasLimit
+				ts.totalTxBytes += txSize
+				ts.selectedTxs = append(ts.selectedTxs, txBz)
+			}
+		} else {
+			ts.totalTxBytes += txSize
+			ts.selectedTxs = append(ts.selectedTxs, txBz)
+		}
+	}
+
+	// check if we've reached capacity; if so, we cannot select any more transactions
+	return ts.totalTxBytes >= maxTxBytes || (maxBlockGas > 0 && (ts.totalTxGas >= maxBlockGas))
+}

baseapp/abci_utils_test.go

@@ -8,14 +8,22 @@ import (
 	"github.com/cometbft/cometbft/crypto/secp256k1"
 	cmtprotocrypto "github.com/cometbft/cometbft/proto/tendermint/crypto"
 	cmtproto "github.com/cometbft/cometbft/proto/tendermint/types"
+	dbm "github.com/cosmos/cosmos-db"
 	protoio "github.com/cosmos/gogoproto/io"
 	"github.com/cosmos/gogoproto/proto"
 	"github.com/golang/mock/gomock"
 	"github.com/stretchr/testify/suite"
 
+	"cosmossdk.io/log"
+
 	"github.com/cosmos/cosmos-sdk/baseapp"
+	baseapptestutil "github.com/cosmos/cosmos-sdk/baseapp/testutil"
 	"github.com/cosmos/cosmos-sdk/baseapp/testutil/mock"
+	codectestutil "github.com/cosmos/cosmos-sdk/codec/testutil"
+	"github.com/cosmos/cosmos-sdk/testutil/testdata"
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/types/mempool"
+	authtx "github.com/cosmos/cosmos-sdk/x/auth/tx"
 )
 
 const (
@@ -274,6 +282,93 @@ func (s *ABCIUtilsTestSuite) TestValidateVoteExtensionsTwoVotesNilAbsent() {
 	s.Require().Error(baseapp.ValidateVoteExtensions(s.ctx, s.valStore, 3, chainID, llc))
 }
 
+func (s *ABCIUtilsTestSuite) TestDefaultProposalHandler_NoOpMempoolTxSelection() {
+	// create a codec for marshaling
+	cdc := codectestutil.CodecOptions{}.NewCodec()
+	baseapptestutil.RegisterInterfaces(cdc.InterfaceRegistry())
+
+	// create a baseapp along with a tx config for tx generation
+	txConfig := authtx.NewTxConfig(cdc, authtx.DefaultSignModes)
+	app := baseapp.NewBaseApp(s.T().Name(), log.NewNopLogger(), dbm.NewMemDB(), txConfig.TxDecoder())
+
+	// create a proposal handler
+	ph := baseapp.NewDefaultProposalHandler(mempool.NoOpMempool{}, app)
+	handler := ph.PrepareProposalHandler()
+
+	// build a tx
+	_, _, addr := testdata.KeyTestPubAddr()
+	builder := txConfig.NewTxBuilder()
+	s.Require().NoError(builder.SetMsgs(
+		&baseapptestutil.MsgCounter{Counter: 0, FailOnHandler: false, Signer: addr.String()},
+	))
+	builder.SetGasLimit(100)
+	setTxSignature(s.T(), builder, 0)
+
+	// encode the tx to be used in the proposal request
+	tx := builder.GetTx()
+	txBz, err := txConfig.TxEncoder()(tx)
+	s.Require().NoError(err)
+	s.Require().Len(txBz, 152)
+
+	testCases := map[string]struct {
+		ctx         sdk.Context
+		req         *abci.RequestPrepareProposal
+		expectedTxs int
+	}{
+		"small max tx bytes": {
+			ctx: s.ctx,
+			req: &abci.RequestPrepareProposal{
+				Txs:        [][]byte{txBz, txBz, txBz, txBz, txBz},
+				MaxTxBytes: 10,
+			},
+			expectedTxs: 0,
+		},
+		"small max gas": {
+			ctx: s.ctx.WithConsensusParams(cmtproto.ConsensusParams{
+				Block: &cmtproto.BlockParams{
+					MaxGas: 10,
+				},
+			}),
+			req: &abci.RequestPrepareProposal{
+				Txs:        [][]byte{txBz, txBz, txBz, txBz, txBz},
+				MaxTxBytes: 456,
+			},
+			expectedTxs: 0,
+		},
+		"large max tx bytes": {
+			ctx: s.ctx,
+			req: &abci.RequestPrepareProposal{
+				Txs:        [][]byte{txBz, txBz, txBz, txBz, txBz},
+				MaxTxBytes: 456,
+			},
+			expectedTxs: 3,
+		},
+		"max gas and tx bytes": {
+			ctx: s.ctx.WithConsensusParams(cmtproto.ConsensusParams{
+				Block: &cmtproto.BlockParams{
+					MaxGas: 200,
+				},
+			}),
+			req: &abci.RequestPrepareProposal{
+				Txs:        [][]byte{txBz, txBz, txBz, txBz, txBz},
+				MaxTxBytes: 456,
+			},
+			expectedTxs: 2,
+		},
+	}
+
+	for name, tc := range testCases {
+		s.Run(name, func() {
+			// iterate multiple times to ensure the tx selector is cleared each time
+			for i := 0; i < 5; i++ {
+				resp, err := handler(tc.ctx, tc.req)
+				s.Require().NoError(err)
+				s.Require().Len(resp.Txs, tc.expectedTxs)
+			}
+		})
+	}
+}
+
 func marshalDelimitedFn(msg proto.Message) ([]byte, error) {
 	var buf bytes.Buffer
 	if err := protoio.NewDelimitedWriter(&buf).WriteMsg(msg); err != nil {

baseapp/baseapp.go

@@ -1092,6 +1092,14 @@ func (app *BaseApp) ProcessProposalVerifyTx(txBz []byte) (sdk.Tx, error) {
 	return tx, nil
 }
 
+func (app *BaseApp) TxDecode(txBytes []byte) (sdk.Tx, error) {
+	return app.txDecoder(txBytes)
+}
+
+func (app *BaseApp) TxEncode(tx sdk.Tx) ([]byte, error) {
+	return app.txEncoder(tx)
+}
+
 // Close is called in start cmd to gracefully cleanup resources.
 func (app *BaseApp) Close() error {
 	var errs []error