estimate the gasLimit for calling a function in a smartcontract ethers.js is erroring out

[ishan-verma]

I'm trying to estimate the gasLimit for calling a function in a smartcontract but ethers.js is erroring out
[Error caught attackArbitrageOpportunity: Error: cannot estimate gas; transaction may fail or may require manual gas limit (method="estimateGas", transaction={"from":"0x652694fe1f10D0dEc1BGR9496bB7220d7799","gasPrice":{"type":"BigNumber","hex":"0x1f4add4dac"},"to":"0x8Daa352694fe1f10D549d4B496b8f0a38B76668a3106","data":"0x0c5c9fa800000000000000000000a0b86991c6218b36
here is the code

const smartContract = new ethers.Contract(contractAddress, contractABI.abi, this.signer)
const transactionOptions = {
               gasPrice: gasPrice

           }
const tempgasfixlimit = await smartContract.estimateGas.functionInOurSmartContract(fromToken, fromAmount, params, transactionOptions)
       console.log("magic:",tempgasfixlimit)

[ricmoo]

What signer are you using? Ethers should t be emitting anything with the error attackArbitrageOpportunity.

What provider are you using?

[ishan-verma]

attackArbitrageOpportunity i just a console.log that I added. Here is signer and provider code

const ethChainProvider = new ethers.getDefaultProvider(
        "homestead",
        constants.WEB_SOCKET_ADDRESS
      );
 const signer = new ethers.Wallet(privateKey, ethChainProvider)

[ricmoo]

Oh! I see. :)

This error just means your node cannot guess how much it will cost to run the transaction. This can happen for a few reasons; 1) if there is a revert in your contract, it may be getting triggered, 2) the execution cost of the transaction exceeds the configured transaction or block gas limit, 3) sometimes a node seems to just “give up” on estimating, often (bit not always?) when it calls out to other contracts.

Do any of those cases seem possible?

[ricmoo]

(I just noticed too, there does not seem to be a contract deployed to that address on mainnet. Did you forget to deploy it?) sorry looked at the from address instead of the to.

[ishan-verma]

thanks for your response! is there a way to calculate gas limit for calling this function? do you think it is worth checking out estimateGas function of web or something similar?

[ricmoo]

The estimateGas function just calls the estimateGas of the provider, so there is nothing interesting internal to examine. And that just simulates the execution in the Provider’s node, which runs the EVM code with the available blockchain data (contract data, bytecode, etc). Also make sure your node is synced.

The best thing to do is to look at the contract source to figure out what could be unpredictable.

If you are certain the contract will succeed, you can try using a much higher gas limit for now to get an idea of how mu it will cost, then you can hard-code a reasonable worst-case value. I generally use values baked into the ABI.

[amankaushik0874]

what if the transaction is using 30 Million gas. it's the highest number for a block, How to increase after that. I am writing huge number of data. But still the transaction cost of using 30 Million gas is $0.04, I think I can increase the gas limit if possible. Any solution @ricmoo ?

[EvilJordan]

Given that output error from @ishan-verma, how does one parse it since it's all returned as a string?

[Error caught attackArbitrageOpportunity: Error: cannot estimate gas; transaction may fail or may require manual gas limit (method="estimateGas", transaction={"from":"0x652694fe1f10D0dEc1BGR9496bB7220d7799","gasPrice":{"type":"BigNumber","hex":"0x1f4add4dac"},"to":"0x8Daa352694fe1f10D549d4B496b8f0a38B76668a3106","data":"0x0c5c9fa800000000000000000000a0b86991c6218b36

[ricmoo]

Parse the error.message? It is intended as a human-readable error. Many of those properties are available on the actual error object though. The main thing I expect people to look at programmatically is the error.code which will match one of the error codes.

[EvilJordan]

Parse the error. The error return object is that entire string, so there's no way to call error.code or error.message... unless I've done something horribly wrong (same issue as with #1237 (comment))

[ricmoo]

@EvilJordan Can you provide a concise example? I’m not sure where in that sample you are getting a string thrown. If that is the case, it is certainly a bug.

If you use string concatenation with an error (e.g. console.log("error: " + error)), it is coerced into a string.

[KeerthanaRamalingam]

I am tried calling a function in my smart contract, and for estimating gas for a function, I used the below code and its worked,

        // Raw Transaction
        var rawTx = {
            nonce: nonce
        };

        // Gas limit
        let findgaslimit = await provider.estimateGas(signature, destination, data, rawTx);
        rawTx.gasLimit = findgaslimit;
        
        // Populate Transaction
        let unsignedTx = await contractInstance.populateTransaction.forward(signature, destination, data, rawTx)

        // Send Transaction
        let response = await wallet.sendTransaction(unsignedTx);
        await response.wait();

Hope it helps!

[pawangspandey]

I think we don't even need to pass the gas limit and gas price as it can be automatically set.
Source: https://docs.ethers.io/v5/api/contract/contract/#contract-functionsSend
But we can override the gas limit and gas price.

Example with overridden gas limit and gas price.

   contract.methodName(
     params,
    { gasLimit: ethers.utils.hexlify(250000), gasPrice: ethers.utils.parseUnits('5', "gwei") },
     );

with automated gas limit and gas price set by ether

   contract.methodName(
     params
     );

Hope this will help.

[layonthebeech]

Can you read the smart contract without paying gas?

[OxQuasar]

Yes this ^ is what I want to know as well. I'm calling a Uniswap GetAmountsOut function which should not require gas to run, but I'm still getting a gas error. With no gas override I get a unpredictable gas limit error. With a gas override I get a insufficient funds error (my account has funds).