multiCall.js

The multiCall.js file has one function executeTryMultiCall() that calls all RPC URLs for a chain in parallel using promises. Workers can can execute it once per chain using their own promises to get responses for all chains at once. See a simple code example in the pricesWorker.

Each call to executeTryMultiCall() can call one or more functions (declared in the parameter contractCalls) but only on a single contract for the chain passed. See the code comments at the top of the multiCall.js file to learn more about how to use multiCall.js.

 * @param {*} chain - target chain to call
 * @param {*} contractAddress - target contract address on the chain to call
 * @param {*} contractAbi - target contract abi
 * @param {*} contractCalls - encoded function calls on the contract
 * @param {*} updateDbFlag - whether or not to update the RPC provider database info
 * @returns new Promise (fulfilled or rejected)

Workflow

Execute the contractCalls for all chain RPC URLs using internal promises.
For each RPC URL gets its last block number and networkID and stored then a callData array
Places the return values for the contractCalls into the callData array.
If all PRC URLs fail then the return promise is tagged as promise.status === 'rejected' and the callData will contain the error message for each RPC URL.
If the all RPC URLS succeed then the callData array will have rows for the results of all callData and the promise tagged as promise.status === 'fulfilled'. The callData is returned with the top row having the hightest block number.
If some RPC URLs fail then the callData will have a mixture of callData values and RPC URL error messages and the promise tagged as promise.status === 'fulfilled'. The callData is returned with the top row having the hightest block number and the RPC URLS that errored at the bottom of the callData array.

If updateDbFlag is true then the RPC provider info, for the chain, will be updated in the database CHAINS table.

"providers": {
    "rpc": {
        "https://rpc.apechain.com/http": {
            "health": true,
            "runtime": 0.706,
            "networkId": 33139,
            "blockNumber": 21227946
        },
        ...
    }
}

Workflow​

Workflow