@0xsequence/multicall

An Ethereum provider wrapper that aggregates multiple operations in one, reducing the network load on clients and servers. The project aims to be plug-and-play with existing ether.js integrations.

For more info see 0xsequence project page.

Inspired by MakerDAO Multicall.js.

Installation

yarn add @0xsequence/multicall

or

npm install --save @0xsequence/multicall

Usage

Sequence Multicall works by implementing ethers.Provider and wrapping an existing ethers.Provider; this wrapped provider can transparently aggregate supported JSON-RPC calls.

import { providers } from '@0xsequence/multicall'
import { providers as ethersProviders } from 'ethers'

// MulticallProvider can wrap and extend with multicall functionality
// any ethers.js provider, it's not limited to JsonRpcProvider
const provider = new providers.MulticallProvider(new ethersProviders.JsonRpcProvider("https://cloudflare-eth.com/"))

Making aggregated calls

Multicall leverages RPC calls' asynchronous nature to perform the aggregation; it implements a buffer with a configurable 50ms delay and aggregates all operations received within that window.

Explicit usage of the functionality can be forced by making multiple calls using Promise.all.

// Both requests are aggregated into a single RPC call
const [balance, supply] = await Promise.all([
  provider.getBalance("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2"),
  dai.totalSupply()
])

Methods can also be aggregated without using Promise.all, as long as there are no await in between calls.

// DON'T
const balance = await provider.getBalance("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2")
const supply = await dai.totalSupply()

// DO
const balancePromise = provider.getBalance("0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2")
const supplyPromise = dai.totalSupply()

const balance = await balancePromise
const supply = await supplyPromise

Using the provider

The MulticallProvider instance can be used in any context where an ethers.Provider is expected, including contract interfaces, middlewares, or libraries; all calls to the same provider are candidates for aggregation.

// Uses a single JSON-RPC call

const abi = [
    "function balanceOf(address owner) view returns (uint256)",
    "function totalSupply() view returns (uint256)",
    "function symbol() view returns (string)",
]

const uni = new ethers.Contract("0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984", abi, provider)
const dai = new ethers.Contract("0x6B175474E89094C44Da98b954EedeAC495271d0F", abi, provider)

const uniTotalSupplyPromise = uni.totalSupply()

const [totalSupply, balance, daiSymbol, uniSymbol] = await Promise.all([
  dai.totalSupply(),
  dai.balanceOf("0xAb5801a7D398351b8bE11C439e05C5B3259aeC9B"),
  dai.symbol(),
  uni.symbol()
])

const uniTotalSupply = await uniTotalSupplyPromise

Supported methods

The following JSON-RPC methods are supported for call aggregation:

All other RPC methods that are part of the standard are forwarded to the parent provider without any modifications.

⚠️ Using mixed blocktags will make some calls skip aggregation.

Error handling

The multicall wrapper is designed to work with any exiting ether.js integration transparently; this includes error handling for cases when multicall fails, is wrongly configured, or the contract does not support it.

JSON-RPC Calls are forwarded to the parent provider on any of the following cases:

• Multicall contract is not deployed on the given network
• Individual call fails (only failed calls are forwarded)
• Batch call fails (all calls are forwarded)
• Invalid RPC Call (invalid address, etc.)
• Mixed blocktags within a batch
• Unsupported special parameters (see supported methods)
• Unsupported method

Configuration

The MulticallProvider comes with a pre-defined configuration; it's ready to work out-of-the-box on the networks: Mainnet, Ropsten, Kovan, Rinkeby, Görli, and Matic (Mainnet).

DEFAULT_CONF = {
  batchSize: 50,
  timeWindow: 50, // ms
  contract: "0xCa731e0f33Afbcfa9363d6F7449d1f5447d10C80"
}

Supported networks

The utility contract is 0xCa731e0f33Afbcfa9363d6F7449d1f5447d10C80, it has been deployed using an Universal Deployer and it uses the same address on all networks. It can be used on any of these chains without configuration changes.

It can be deployed on any network that supports the CREATE2 opcode.