Best Practices for Recommendation regarding Gas Price & Limit in a Dapp

Question

I am developing a Dapp. I was wondering what are the best practices for user recommendation regarding gas price and limit in such a Dapp? Should I be using the following methods in my contract, or should I rely on the user's wallet (e.g. MetaMask) to recommend these values to the users? What are the pros and cons of each technique? In which scenarios should I use one instead of the other?

 web3.eth.getGasPrice([callback])
 myContract.methods.myMethod().estimateGas()

Thank you. J

Answer 1

My recommendation:

Configure gas-price according to user-input, allowing for the current price as default (you'll need to implement function scan):

async function getGasPrice(web3) {
    while (true) {
        const nodeGasPrice = await web3.eth.getGasPrice();
        const userGasPrice = await scan(`Enter gas-price or leave empty to use ${nodeGasPrice}: `);
        if (/^\d+$/.test(userGasPrice))
            return userGasPrice;
        if (userGasPrice == '')
            return nodeGasPrice;
        console.log('Illegal gas-price');
    }
}

Configure gas-limit using estimateGas, but capped with a minimum threshold in order to handle inaccurate estimations:

const MIN_GAS_LIMIT = 100000;

async function getGasLimit(web3, transaction, userAddress, value = 0) {
    const gasLimit = await transaction.estimateGas({from: userAddress, value: value});
    return Math.max(gasLimit, MIN_GAS_LIMIT);
}