update metadata implementation

services/construction/metadata.go

@@ -117,23 +117,24 @@ func (a *APIService) ConstructionMetadata(
 		return nil, svcErrors.WrapErr(svcErrors.ErrGeth, err)
 	}
 
+	// Ensure the gas tip is at least 30 gwei. This is the minimum gas price recommended by the Polygon team.
+	// See https://forum.polygon.technology/t/recommended-min-gas-price-setting/7604 for additional context.
+	// This minimum must be applied to the tip, not the cap to effectivley mitigate spam (since the tip goes to miners)
+	minTip := big.NewInt(30000000000) // 30 gwei
+	if minTip.Cmp(gasTip) == 1 {
+		gasTip = minTip
+	}
+
 	var gasCap *big.Int
 	if input.GasCap == nil {
-		// Set default max fee to double the last base fee plus priority tip
+		// Set default max fee to double the last base fee plus multiplied priority tip
 		// to ensure tx is highly likely to go out in the next block.
 		multiplier := big.NewInt(2)
 		gasCap = new(big.Int).Add(gasTip, new(big.Int).Mul(header.BaseFee, multiplier))
 	} else {
 		gasCap = input.GasCap
 	}
 
-	// Ensure the gas cap is at least 30 gwei, the minimum gas price that the node will accept on mainnet.
-	// See https://forum.polygon.technology/t/recommended-min-gas-price-setting/7604 for additional context.
-	minFee := big.NewInt(30000000000) // 30 gwei
-	if minFee.Cmp(gasCap) == 1 {
-		gasCap = minFee
-	}
-
 	metadata := &metadata{
 		Nonce:           nonce,
 		GasLimit:        gasLimit,
@@ -152,7 +153,7 @@ func (a *APIService) ConstructionMetadata(
 	}
 
 	// Find suggested gas usage. Note that this figure accounts for the minimum (30 gwei), and
-	// is potentially doubled the block base fee.
+	// is potentially double the block base fee.
 	suggestedFee := gasCap.Int64() * int64(gasLimit)
 
 	return &types.ConstructionMetadataResponse{