Support a 'gas multiplier' which can be used to increase gasLimit

[JasperTimm]

Hi there,

Other libraries like Truffle and Web3 support a 'gas multiplier', so that the default gasLimit sent to the provider is:

gasLimit = gasEstimate * GAS_MULTIPLIER

(1.25 for Truffle and 1.5 for Web3 by default I believe, but they can be set)

Are there plans for ethers to support something like this? I have a few transactions which use a few proxy calls to other contracts and the estimate is sometimes not enough, hence the reason for being able to uniformly increase the suggested gas across all transactions.

[Ty-Sir]

I was just thinking the same thing. Here's a makeshift version I am using for my current project where the user sets 'speedyTx' true in local storage upon connecting their wallet to the dapp.

const speedUpTx = (gasPrice) => {
  const isSpeedyOn = window.localStorage.getItem('speedyTx');
  let newGasPrice;
  if(isSpeedyOn === "true"){
    newGasPrice = Math.round(gasPrice * 1.3);
  } else {
    newGasPrice = Math.round(gasPrice * 1);
  }
  newGasPrice = newGasPrice.toString(16);
  return "0x".concat(newGasPrice);
}

const rollDice = async () => {
  try{
    const price = await props.web3.getGasPrice();
    const newPrice = speedUpTx(price);
    const writeInstance = new ethers.Contract(GameAddress, abi.Game, signer);
    const roll = await writeInstance.rollDice({from: account, gasPrice: newPrice});
    const result = await roll.wait(2);
    if(result.status === 1) {
      //do sutff
    }
  } catch(error){
    console.log(error.message)
}

[JasperTimm]

Hey @Ty-Sir - gasPrice is not quite the same as gasLimit. Your implementation is for increasing the gasPrice of the transaction to ensure it gets taken up quickly right?

My problem is a little different - the gasLimit is the amount of gas the transaction can use before it runs out of gas and reverts. This is normally set by an estimate given by the network but in some cases the estimate is not enough.

[Ty-Sir]

Yes you are correct, I misread your question as gasPrice not gasLimit. Been debugging far too long atm 😵‍💫

[ricmoo]

I haven’t heard of this before in other libraries, but is definitely something I used to do manually before in some of my old projects.

I changed this tactic to instead include the gas property in my ABI, since when the gas estimation goes awry, I often found a multiplier didn’t always solve the problem anyways, and setting an explicit gas in the ABI also saves the estimate call.

But can you link to the docs for the multiplier in the other projects that do this? One concern I have are using IEEE 754 decimal numbers, which would mean rounding, but since it’s an approximation, this is likely fine, but I’d like to see how and when other projects are using this. :)

[JasperTimm]

Sure!

Truffle: https://trufflesuite.com/docs/truffle/reference/contract-abstractions#mycontractgasmultipliergas_multiplier
Hardhat: https://hardhat.org/config/ (search for gasMultiplier)
Web3: From experimentation it looks like the default is 1.5 but I can't see it referenced in the docs...

Out of curiosity @ricmoo - can you show a quick example of including the gas in the ABI? Is that something Solidity supports?

[zemse]

[
   {
        "constant": false,
        "inputs": [
            {
                "name": "_from",
                "type": "address"
            },
            {
                "name": "_to",
                "type": "address"
            },
            {
                "name": "_value",
                "type": "uint256"
            }
        ],
        "name": "transferFrom",
        "outputs": [
            {
                "name": "",
                "type": "bool"
            }
        ],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function",
        "gas": 80000 // you can just add this property here
    }
]

[JasperTimm]

Ah ok, this is just manually editing the ABI to add a 'gas' property, I see. I thought there would be some fancy way of specifying it in Solidity so it gets included in the ABI.

Cheers @zemse !

[zemse]

@JasperTimm You can simply extend the provider class to add a gas multiplier. Then you can just use this provider wherever in you code and it should have the multiplier.

class JsonRpcProviderWithIncreasedGasLimit extends JsonRpcProvider {
    async estimateGas(transaction) {
        const actualResult = await super.estimateGas(transaction);
        return actualResult * 2;
    }
}

[JasperTimm]

Thanks @zemse, I agree that's a good solution for the time being. I think it's worth considering integrating a gas multiplier into all providers as part of ethers.js though.