gas exceeds allowance

Question

I'm testing my smart contract on ropsten and I have written an async function that lets me send TRANSACTION transactions from TRANSACTION different accounts. For some reason when TRANSACTION > 20 i get caught in the catch statment with a gas exceeds allowance error and i can't figure out why. I have similarly written a function to fund an arbitrary amount of accounts with eth. Litterally all that is done on the smart contract when invoking instance.methods.addSubmission... is push a uint256 into an array in a mapping(uint256 => uint256[])

async function multipleTx() {
  let accounts = await web3.eth.getAccounts()
  console.log('Issuing Transactions...')
  let totalGasUsed = 0
  const promisesArr = []
  const sendBlockNumber = await web3.eth.getBlockNumber()
  const sendTimeStamp = Date.now()

  for (let i = 0; i < TRANSACTIONS; i++) {
    console.log('account', i, 'is', accounts[i])
    promisesArr.push(
      instance.methods.addSubmissionNoCheck(1, 139).send({
        from: accounts[i],
        gasPrice: 10000000000,
      })
    )
  }
  await Promise.all(promisesArr)
    .then(async (receipts) => {
      let lastBlock = receipts[0].blockNumber
      receipts.forEach((receipt) => {
        totalGasUsed += receipt.gasUsed
        lastBlock =
          receipt.blockNumber > lastBlock ? receipt.blockNumber : lastBlock
      })
      await outputResults(
        sendTimeStamp,
        totalGasUsed,
        sendBlockNumber,
        lastBlock
      )
    })
    .catch((error) => {
      console.log('multipleTX():', error)
    })
}

console output:

multipleTX(): Error: gas required exceeds allowance (8000029) or always failing
transaction
    at C:\Users\Diddi\Documents\mjukvaruteknik\examensarbete\tqdt33\node_modules
\@truffle\hdwallet-provider\node_modules\web3-provider-engine\subproviders\provi
der.js:18:36
    at XMLHttpRequest.request.onreadystatechange (C:\Users\Diddi\Documents\mjukv
aruteknik\examensarbete\tqdt33\node_modules\web3-providers-http\src\index.js:96:
13)
    at XMLHttpRequestEventTarget.dispatchEvent (C:\Users\Diddi\Documents\mjukvar
uteknik\examensarbete\tqdt33\node_modules\xhr2-cookies\xml-http-request-event-ta
rget.ts:44:13)
    at XMLHttpRequest._setReadyState (C:\Users\Diddi\Documents\mjukvaruteknik\ex
amensarbete\tqdt33\node_modules\xhr2-cookies\xml-http-request.ts:219:8)
    at XMLHttpRequest._onHttpResponseEnd (C:\Users\Diddi\Documents\mjukvarutekni
k\examensarbete\tqdt33\node_modules\xhr2-cookies\xml-http-request.ts:345:8)
    at IncomingMessage.<anonymous> (C:\Users\Diddi\Documents\mjukvaruteknik\exam
ensarbete\tqdt33\node_modules\xhr2-cookies\xml-http-request.ts:311:39)
    at IncomingMessage.emit (events.js:228:7)
    at endReadableNT (_stream_readable.js:1185:12)
    at processTicksAndRejections (internal/process/task_queues.js:81:21)

smart contract function

mapping(uint256 => uint256[]) public submissions;

function addSubmissionNoCheck(uint256 key, uint256 timeAtLocation) external {
  submissions[key].push(timeAtLocation);
}

Update:

I have removed the gas limit specification as per my own solution below and instead and overfunded the accounts and it seems to work now. I've ran multiple times doing 20 transactions from 20 different accounts. However i feel like if the problem was insufficent funds in the accounts i should receive the Insufficient funds for gas * price + value error.

Answer 1

I seem to have solved my issues by setting a lower gas limit on each of the transactions such that they sum up to a gas limit lower than 8,000,000 GAS which is the gas limit of a block. So for instance, with 20 transactions, i set it to 75000since I saw based on the receipts my tx costs in the worst case my addSubmission function costs 69095. 75000 * 20 < 8,000,000 and it went through.

Why did it work? Thoughts

web3 is calculating the potential gas required by taking gas limit * number of transacting accounts and if this exceeds block gas limit it fails. Now it does work if in the for loop i use the same account then I can fire off 20 transactions without a problem but since i use multiple accounts for whatever reason web3 first caluclates gas limits as if it was separate accounts but then when the promise.All runs it applies the calculated gas such that it's ONE transaction from ONE account and it exceeds the block gas limit and therefore fails. This might be because the walletprovider for the web3 instance uses the same mneumonic? i set it the following way

const walletProvider = new HDWalletProvider(mnemonic, infura.endpoint, 0, 100)
const web3 = new Web3(walletProvider)

Answer 2

This seem to have been entirely a problem with Infura. I suspect it is in regard to their rate limits. Nevertheless we have now set up our own ethereum node using geth and are able to isssue as many transactions as we want pretty much problem free!