How to use JsonRpcBatchProvider

[alex-sumner]

Hi, I am trying to use the JsonRpcBatchProvider and I wondered if anyone would be kind enough to tell me whether I am using it in the intended way?

My code looks like this:

const batchProvider = new ethers.providers.JsonRpcBatchProvider(url);  
const wallet = new ethers.Wallet(privateKey, batchProvider);
const ZERO = BigNumber.from(0)

let wallet: ethers.Signer = getSigner();
let myContract: ethers.Contract = getContract();
let nonce: BigNumber;

async function test() {
  const requests: TransactionRequest[] = [];
  nonce = ZERO;
  for (let i = 0; i < 100; i++) {
    const tx = await getTx(i);
    requests.push(tx);
  }
  const promises: any[] = [];
  for (let tx of requests) {
    promises.push(wallet.sendTransaction(tx));
  }
  await Promise.all(promises);
}

async function getTx(i: number) {
  const txData = myContract.interface.encodeFunctionData("myFunction", [i]);
  const txReq: TransactionRequest = {
    to: myContract.address,
    data: txData,
  };
  const tx = await wallet.populateTransaction(txReq);
  if (nonce.eq(ZERO)) {
    nonce = BigNumber.from(tx.nonce);
  } else {
    nonce = nonce.add(1);
    tx.nonce = nonce;
  }
  return tx;
}

So I populate an array of Promises by repeatedly calling Signer.sendTransaction. I give the transaction for each a nonce one greater than the last, and then await all of them.

I guess my questions are:

1. Does this look right?
2. Is there a better way of doing it?
3. Does anyone have experience of doing it, and any advice on how many requests can go in one batch?
4. Does anyone have experience of, or advice about, doing this on Arbitrum?

Many thanks!