"out of gas" when reading contract method

[niklasnatter]

Hey,
thanks a lot for this library, the API is a pleasure to use!

I am quite new in this space and running into a out of gas error while reading a contract method.
I am trying to read the virtual price of the curve 3pool from the curve registry contract with the following code:

  const ethersProvider = ethers.getDefaultProvider();

  const contract = new ethers.Contract(
    '0x90e00ace148ca3b23ac1bc8c240c2a7dd9c2d7f5',
    curveRegistryABI,
    ethersProvider
  );

  const result = await contract.get_virtual_price_from_lp_token(
    '0x6c3F90f043a72FA612cbac8115EE7e52BDe6E490'
  );

I created a runnable version of the code on StackBlitz here:
https://stackblitz.com/edit/js-yb9cxz?file=index.js

Unfortunately, the call fails to meet the quorum with the following results:

[
   {
      "weight":1,
      "start":1623831102192,
      "error":{
         "reason":"processing response error",
         "code":"SERVER_ERROR",
         "body":"{\"jsonrpc\":\"2.0\",\"id\":42,\"error\":{\"code\":-32000,\"message\":\"out of gas\"}}",
         "error":{
            "code":-32000
         },
         "requestBody":"{\"method\":\"eth_call\",\"params\":[{\"gas\":\"0x60b8\",\"to\":\"0x90e00ace148ca3b23ac1bc8c240c2a7dd9c2d7f5\",\"data\":\"0xc5b7074a0000000000000000000000002fe94ea3d5d4a175184081439753de15aef9d614\"},\"latest\"],\"id\":42,\"jsonrpc\":\"2.0\"}",
         "requestMethod":"POST",
         "url":"https://mainnet.infura.io/v3/84842078b09946638c03157f83405213"
      }
   },
   {
      "weight":1,
      "start":1623831102192,
      "error":{
         "reason":"processing response error",
         "code":"SERVER_ERROR",
         "body":"{\"jsonrpc\": \"2.0\", \"id\": 43, \"error\": {\"code\": -32000, \"message\": \"out of gas\"}}",
         "error":{
            "code":-32000
         },
         "requestBody":"{\"method\":\"eth_call\",\"params\":[{\"gas\":\"0x60b8\",\"to\":\"0x90e00ace148ca3b23ac1bc8c240c2a7dd9c2d7f5\",\"data\":\"0xc5b7074a0000000000000000000000002fe94ea3d5d4a175184081439753de15aef9d614\"},\"latest\"],\"id\":43,\"jsonrpc\":\"2.0\"}",
         "requestMethod":"POST",
         "url":"https://eth-mainnet.alchemyapi.io/v2/_gg7wSSi0KMBsdKnGVfHDueq6xMB9EkC"
      }
   },
   {
      "weight":1,
      "start":1623831104192,
      "error":{
         "reason":"processing response error",
         "code":"SERVER_ERROR",
         "body":"{\"jsonrpc\":\"2.0\",\"id\":43,\"error\":{\"code\":-32000,\"message\":\"out of gas\"}}",
         "error":{
            "code":-32000
         },
         "requestBody":"{\"method\":\"eth_call\",\"params\":[{\"gas\":\"0x60b8\",\"to\":\"0x90e00ace148ca3b23ac1bc8c240c2a7dd9c2d7f5\",\"data\":\"0xc5b7074a0000000000000000000000002fe94ea3d5d4a175184081439753de15aef9d614\"},\"latest\"],\"id\":43,\"jsonrpc\":\"2.0\"}",
         "requestMethod":"POST",
         "url":"https://cloudflare-eth.com/"
      }
   },
   {
      "weight":1,
      "start":1623831104192,
      "result":"0x0000000000000000000000000000000000000000000000000dea6b5f8bba8495"
   }
]

I am sure there is a simple explanation for the behaviour, but I havent found a solution beside setting an explicitgasLimit yet.
Am I doing something wrong?
Do I need to explicitly set the gasLimit for each contract call in the overrides? If yes, how should I estimate the limits?

Thanks in advance!

[zemse]

Such error is also observed when the method doesn't exist on the contract. Can you verify if the address you're using is correct and it contains the method?

[niklasnatter]

Thanks again for the answer! I figured that the ABI that I exported from Etherscan includes a gas property in the method definition:

  {
    name: 'get_virtual_price_from_lp_token',
    outputs: [
      {
        type: 'uint256',
        name: ''
      }
    ],
    inputs: [
      {
        type: 'address',
        name: '_token'
      }
    ],
    stateMutability: 'view',
    type: 'function',
    gas: 2080
  }

When I remove this property from the ABI, the call succeeds and I get the correct result 🥳

I dont have a lot of experience in this space - maybe it is bad practice to export the contract ABI from Etherscan?
Interestingly, this gas property did not make any problem while I was using web3.js. Maybe the property is handled differently in ethers compared to web3.js?

Anyway, I am glad that things are working now - thanks a lot for your fast response!

[zemse]

Seems this is how it is done.

ethers.js/packages/contracts/src.ts/index.ts

Lines 224 to 238 in ce8f1e4

	// If there was no "gasLimit" override, but the ABI specifies a default, use it
	if (tx.gasLimit == null && fragment.gas != null) {
	// Conmpute the intrinisic gas cost for this transaction
	// @TODO: This is based on the yellow paper as of Petersburg; this is something
	// we may wish to parameterize in v6 as part of the Network object. Since this
	// is always a non-nil to address, we can ignore G_create, but may wish to add
	// similar logic to the ContractFactory.
	let intrinsic = 21000;
	const bytes = arrayify(data);
	for (let i = 0; i < bytes.length; i++) {
	intrinsic += 4;
	if (bytes[i]) { intrinsic += 64; }
	}
	tx.gasLimit = BigNumber.from(fragment.gas).add(intrinsic);
	}

[zemse]

the ABI that I exported from Etherscan includes a gas property in the method definition

Oh I think etherscan tried the value for some input, but the input you're using might be causing a longer execution path than usual.

Anyway glad that it's figured out :)

[zemse]

this gas property did not make any problem while I was using web3.js

That could mean web3.js did not use that value. While here ethers.js took the value seriously. This feature is particularly useful if your method is very costly, as some nodes have default gas limit when they go over view methods (to prevent abuse of resources), I think it is about 500,000 or something. So if your method is going to cost more, it can be specified in ABI, and ethers.js can use it without needing an override.

[niklasnatter]

Thanks again for the explanation! 🙂

I will unset the gas property of the Etherscan ABIs before using them for now like this:

etherscanABI.map(item => ({ ...item, gas: undefined }));