From 6ec0a1ba7ce07a9c314a3de87d8b3e42ab1cc1df Mon Sep 17 00:00:00 2001
From: hexoscott <70711990+hexoscott@users.noreply.github.com>
Date: Fri, 2 Dec 2022 15:32:56 +0000
Subject: [PATCH] txpool to consider available gas in Best call (#755)

---
 txpool/pool.go               | 27 ++++++++++++++++++++++++---
 txpool/txpool_grpc_server.go | 17 +++++++++--------
 2 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/txpool/pool.go b/txpool/pool.go
index 0983e5c0d..6c0305f78 100644
--- a/txpool/pool.go
+++ b/txpool/pool.go
@@ -34,6 +34,9 @@ import (
 	"github.com/google/btree"
 	"github.com/hashicorp/golang-lru/simplelru"
 	"github.com/holiman/uint256"
+	"github.com/ledgerwatch/log/v3"
+	"go.uber.org/atomic"
+
 	"github.com/ledgerwatch/erigon-lib/chain"
 	"github.com/ledgerwatch/erigon-lib/common"
 	"github.com/ledgerwatch/erigon-lib/common/cmp"
@@ -47,8 +50,6 @@ import (
 	"github.com/ledgerwatch/erigon-lib/kv/kvcache"
 	"github.com/ledgerwatch/erigon-lib/kv/mdbx"
 	"github.com/ledgerwatch/erigon-lib/types"
-	"github.com/ledgerwatch/log/v3"
-	"go.uber.org/atomic"
 )
 
 var (
@@ -599,7 +600,7 @@ func (p *TxPool) Started() bool                      { return p.started.Load() }
 
 // Best - returns top `n` elements of pending queue
 // id doesn't perform full copy of txs, however underlying elements are immutable
-func (p *TxPool) Best(n uint16, txs *types.TxsRlp, tx kv.Tx, onTopOf uint64) (bool, error) {
+func (p *TxPool) Best(n uint16, txs *types.TxsRlp, tx kv.Tx, onTopOf, availableGas uint64) (bool, error) {
 	// First wait for the corresponding block to arrive
 	if p.lastSeenBlock.Load() < onTopOf {
 		return false, nil // Too early
@@ -615,6 +616,12 @@ func (p *TxPool) Best(n uint16, txs *types.TxsRlp, tx kv.Tx, onTopOf uint64) (bo
 
 		best := p.pending.best
 		for i := 0; j < int(n) && i < len(best.ms); i++ {
+
+			// if we wouldn't have enough gas for a standard transaction then quit out early
+			if availableGas < fixedgas.TxGas {
+				break
+			}
+
 			mt := best.ms[i]
 			if mt.Tx.Gas >= p.blockGasLimit.Load() {
 				// Skip transactions with very large gas limit
@@ -628,6 +635,20 @@ func (p *TxPool) Best(n uint16, txs *types.TxsRlp, tx kv.Tx, onTopOf uint64) (bo
 				toRemove = append(toRemove, mt)
 				continue
 			}
+
+			// make sure we have enough gas in the caller to add this transaction.
+			// not an exact science using intrinsic gas but as close as we could hope for at
+			// this stage
+			intrinsicGas, _ := CalcIntrinsicGas(uint64(mt.Tx.DataLen), uint64(mt.Tx.DataNonZeroLen), nil, mt.Tx.Creation, true, true)
+			if intrinsicGas > availableGas {
+				// we might find another TX with a low enough intrinsic gas to include so carry on
+				continue
+			}
+
+			if intrinsicGas <= availableGas { // check for potential underflow
+				availableGas -= intrinsicGas
+			}
+
 			txs.Txs[j] = rlpTx
 			copy(txs.Senders.At(j), sender)
 			txs.IsLocal[j] = isLocal
diff --git a/txpool/txpool_grpc_server.go b/txpool/txpool_grpc_server.go
index 40ae62722..1c73a0813 100644
--- a/txpool/txpool_grpc_server.go
+++ b/txpool/txpool_grpc_server.go
@@ -28,12 +28,6 @@ import (
 	grpc_middleware "github.com/grpc-ecosystem/go-grpc-middleware"
 	grpc_recovery "github.com/grpc-ecosystem/go-grpc-middleware/recovery"
 	"github.com/holiman/uint256"
-	"github.com/ledgerwatch/erigon-lib/common"
-	"github.com/ledgerwatch/erigon-lib/gointerfaces"
-	txpool_proto "github.com/ledgerwatch/erigon-lib/gointerfaces/txpool"
-	types2 "github.com/ledgerwatch/erigon-lib/gointerfaces/types"
-	"github.com/ledgerwatch/erigon-lib/kv"
-	"github.com/ledgerwatch/erigon-lib/types"
 	"github.com/ledgerwatch/log/v3"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
@@ -42,6 +36,13 @@ import (
 	"google.golang.org/grpc/keepalive"
 	"google.golang.org/grpc/reflection"
 	"google.golang.org/protobuf/types/known/emptypb"
+
+	"github.com/ledgerwatch/erigon-lib/common"
+	"github.com/ledgerwatch/erigon-lib/gointerfaces"
+	txpool_proto "github.com/ledgerwatch/erigon-lib/gointerfaces/txpool"
+	types2 "github.com/ledgerwatch/erigon-lib/gointerfaces/types"
+	"github.com/ledgerwatch/erigon-lib/kv"
+	"github.com/ledgerwatch/erigon-lib/types"
 )
 
 // TxPoolAPIVersion
@@ -50,7 +51,7 @@ var TxPoolAPIVersion = &types2.VersionReply{Major: 1, Minor: 0, Patch: 0}
 type txPool interface {
 	ValidateSerializedTxn(serializedTxn []byte) error
 
-	Best(n uint16, txs *types.TxsRlp, tx kv.Tx, onTopOf uint64) (bool, error)
+	Best(n uint16, txs *types.TxsRlp, tx kv.Tx, onTopOf, availableGas uint64) (bool, error)
 	GetRlp(tx kv.Tx, hash []byte) ([]byte, error)
 	AddLocalTxs(ctx context.Context, newTxs types.TxSlots, tx kv.Tx) ([]DiscardReason, error)
 	deprecatedForEach(_ context.Context, f func(rlp, sender []byte, t SubPoolType), tx kv.Tx)
@@ -154,7 +155,7 @@ func (s *GrpcServer) Pending(ctx context.Context, _ *emptypb.Empty) (*txpool_pro
 	reply := &txpool_proto.PendingReply{}
 	reply.Txs = make([]*txpool_proto.PendingReply_Tx, 0, 32)
 	txSlots := types.TxsRlp{}
-	if _, err := s.txPool.Best(math.MaxInt16, &txSlots, tx, 0 /* onTopOf */); err != nil {
+	if _, err := s.txPool.Best(math.MaxInt16, &txSlots, tx, 0 /* onTopOf */, math.MaxUint64 /* available gas */); err != nil {
 		return nil, err
 	}
 	var senderArr [20]byte