Await Token Info in Parallel

[bh2smith]

This method is currently inefficient and slow when used to fetch many tokens at once. This could be easily improved by sending out EVM queries in parallel (i.e. with await Promise.all).

dex-contracts/src/fee_token_liquidity.ts

Lines 29 to 51 in f5a3dbc

	for (const id of tokenIds) {
	const tokenAddress = await exchange.tokenIdToAddressMap(id);
	let tokenInfo;
	try {
	const tokenInstance = await ERC20.at(tokenAddress);
	const symbol = await tokenInstance.symbol();
	const decimals = (await tokenInstance.decimals()).toNumber();
	tokenInfo = {
	id: id,
	symbol: symbol,
	decimals: decimals,
	address: tokenAddress,
	};
	} catch (err) {
	// This generic try-catch is essentially a TokenNotFoundError
	// Could occur when the given ID slot is not occupied by a registered token on the exhchange
	// or if the code registered at address occupied by a token slot is not that of and ERC20 token
	tokenInfo = {
	id: id,
	address: tokenAddress,
	};
	}
	tokenObjects.set(id, tokenInfo);

While improving this, it would also be nice to refactor this to use the batch exchange viewer contract changes that were introduced in #860

[nlordell]

I would suggest using https://web3js.readthedocs.io/en/v1.2.9/include_package-core.html?highlight=batch#batchrequest

This would send all the EVM calls to the node in a single batch request, which would (in theory) allow the node to better optimize the access to blockchain data and improve performance even further.

[bh2smith]

Very nice suggestion! Thanks @nlordell. This also means we now have many other places we can improve with this!

[bh2smith]

@nlordell - Not sure that we have access to the web3 artifact from within this method. Is this going to be more involved that originally expected? Do I really want to pass this into the function...?

[nlordell]

Not sure that we have access to the web3 artifact from within this method

I think you have access to the underlying Web3 contract instance with instance.contract.