mempool: make max_msg_bytes configurable (#3826)

* mempool: make max_msg_bytes configurable

* apply suggestions from code review

* update changelog pending

* apply suggestions from code review again

mempool/clist_mempool.go

@@ -220,9 +220,10 @@ func (mem *CListMempool) CheckTxWithInfo(tx types.Tx, cb func(*abci.Response), t
 	var (
 		memSize  = mem.Size()
 		txsBytes = mem.TxsBytes()
+		txSize   = len(tx)
 	)
 	if memSize >= mem.config.Size ||
-		int64(len(tx))+txsBytes > mem.config.MaxTxsBytes {
+		int64(txSize)+txsBytes > mem.config.MaxTxsBytes {
 		return ErrMempoolIsFull{
 			memSize, mem.config.Size,
 			txsBytes, mem.config.MaxTxsBytes}
@@ -231,8 +232,8 @@ func (mem *CListMempool) CheckTxWithInfo(tx types.Tx, cb func(*abci.Response), t
 	// The size of the corresponding amino-encoded TxMessage
 	// can't be larger than the maxMsgSize, otherwise we can't
 	// relay it to peers.
-	if len(tx) > maxTxSize {
-		return ErrTxTooLarge
+	if max := calcMaxTxSize(mem.config.MaxMsgBytes); txSize > max {
+		return ErrTxTooLarge{max, txSize}
 	}
 
 	if mem.preCheck != nil {

mempool/clist_mempool_test.go

@@ -426,6 +426,9 @@ func TestMempoolMaxMsgSize(t *testing.T) {
 	mempl, cleanup := newMempoolWithApp(cc)
 	defer cleanup()
 
+	maxMsgSize := mempl.config.MaxMsgBytes
+	maxTxSize := calcMaxTxSize(mempl.config.MaxMsgBytes)
+
 	testCases := []struct {
 		len int
 		err bool
@@ -462,7 +465,7 @@ func TestMempoolMaxMsgSize(t *testing.T) {
 			require.NoError(t, err, caseString)
 		} else {
 			require.True(t, len(encoded) > maxMsgSize, caseString)
-			require.Equal(t, err, ErrTxTooLarge, caseString)
+			require.Equal(t, err, ErrTxTooLarge{maxTxSize, testCase.len}, caseString)
 		}
 	}
 

mempool/errors.go

@@ -9,11 +9,18 @@ import (
 var (
 	// ErrTxInCache is returned to the client if we saw tx earlier
 	ErrTxInCache = errors.New("Tx already exists in cache")
-
-	// ErrTxTooLarge means the tx is too big to be sent in a message to other peers
-	ErrTxTooLarge = fmt.Errorf("Tx too large. Max size is %d", maxTxSize)
 )
 
+// ErrTxTooLarge means the tx is too big to be sent in a message to other peers
+type ErrTxTooLarge struct {
+	max    int
+	actual int
+}
+
+func (e ErrTxTooLarge) Error() string {
+	return fmt.Sprintf("Tx too large. Max size is %d, but got %d", e.max, e.actual)
+}
+
 // ErrMempoolIsFull means Tendermint & an application can't handle that much load
 type ErrMempoolIsFull struct {
 	numTxs int

mempool/reactor.go

@@ -19,8 +19,7 @@ import (
 const (
 	MempoolChannel = byte(0x30)
 
-	maxMsgSize = 1048576        // 1MB TODO make it configurable
-	maxTxSize  = maxMsgSize - 8 // account for amino overhead of TxMessage
+	aminoOverheadForTxMessage = 8
 
 	peerCatchupSleepIntervalMS = 100 // If peer is behind, sleep this amount
 
@@ -156,7 +155,7 @@ func (memR *Reactor) RemovePeer(peer p2p.Peer, reason interface{}) {
 // Receive implements Reactor.
 // It adds any received transactions to the mempool.
 func (memR *Reactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
-	msg, err := decodeMsg(msgBytes)
+	msg, err := memR.decodeMsg(msgBytes)
 	if err != nil {
 		memR.Logger.Error("Error decoding message", "src", src, "chId", chID, "msg", msg, "err", err, "bytes", msgBytes)
 		memR.Switch.StopPeerForError(src, err)
@@ -263,9 +262,9 @@ func RegisterMempoolMessages(cdc *amino.Codec) {
 	cdc.RegisterConcrete(&TxMessage{}, "tendermint/mempool/TxMessage", nil)
 }
 
-func decodeMsg(bz []byte) (msg MempoolMessage, err error) {
-	if len(bz) > maxMsgSize {
-		return msg, fmt.Errorf("Msg exceeds max size (%d > %d)", len(bz), maxMsgSize)
+func (memR *Reactor) decodeMsg(bz []byte) (msg MempoolMessage, err error) {
+	if l := len(bz); l > memR.config.MaxMsgBytes {
+		return msg, ErrTxTooLarge{memR.config.MaxMsgBytes, l}
 	}
 	err = cdc.UnmarshalBinaryBare(bz, &msg)
 	return
@@ -282,3 +281,9 @@ type TxMessage struct {
 func (m *TxMessage) String() string {
 	return fmt.Sprintf("[TxMessage %v]", m.Tx)
 }
+
+// calcMaxTxSize returns the max size of Tx
+// account for amino overhead of TxMessage
+func calcMaxTxSize(maxMsgSize int) int {
+	return maxMsgSize - aminoOverheadForTxMessage
+}