rpc: Update GetGasPrice RPC endpoint with global MinGasPrice (#1108)

* return MinGasPrice as minium on GetGasPrice api

* update logic

* update changelog

* globalmingsprice comment

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

rpc/backend/backend.go

@@ -69,6 +69,7 @@ type EVMBackend interface {
 	GetTxByTxIndex(height int64, txIndex uint) (*tmrpctypes.ResultTx, error)
 	EstimateGas(args evmtypes.TransactionArgs, blockNrOptional *types.BlockNumber) (hexutil.Uint64, error)
 	BaseFee(height int64) (*big.Int, error)
+	GlobalMinGasPrice() (sdk.Dec, error)
 
 	// Fee API
 	FeeHistory(blockCount rpc.DecimalOrHex, lastBlock rpc.BlockNumber, rewardPercentiles []float64) (*types.FeeHistoryResult, error)

rpc/backend/evm_backend.go

@@ -818,6 +818,15 @@ func (b *Backend) BaseFee(height int64) (*big.Int, error) {
 	return res.BaseFee.BigInt(), nil
 }
 
+// GlobalMinGasPrice returns MinGasPrice param from FeeMarket
+func (b *Backend) GlobalMinGasPrice() (sdk.Dec, error) {
+	res, err := b.queryClient.FeeMarket.Params(b.ctx, &feemarkettypes.QueryParamsRequest{})
+	if err != nil {
+		return sdk.ZeroDec(), err
+	}
+	return res.Params.MinGasPrice, nil
+}
+
 // FeeHistory returns data relevant for fee estimation based on the specified range of blocks.
 func (b *Backend) FeeHistory(
 	userBlockCount rpc.DecimalOrHex, // number blocks to fetch, maximum is 100

rpc/namespaces/ethereum/eth/api.go

@@ -211,6 +211,16 @@ func (e *PublicAPI) GasPrice() (*hexutil.Big, error) {
 		result = big.NewInt(e.backend.RPCMinGasPrice())
 	}
 
+	// return at least GlobalMinGasPrice from FeeMarket module
+	minGasPrice, err := e.backend.GlobalMinGasPrice()
+	if err != nil {
+		return nil, err
+	}
+	minGasPriceInt := minGasPrice.BigInt()
+	if result.Cmp(minGasPriceInt) < 0 {
+		result = minGasPriceInt
+	}
+
 	return (*hexutil.Big)(result), nil
 }