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2.4.4 • Public • Published

Web3 Functions SDK & Hardhat Plugin

This SDK allows builders to build & run Web3 Functions as well as provides a hardhat plugin for ease integration in Hardhat developer environments:

Getting Started with Web3 Functions

Project Setup

  1. Install project dependencies
yarn install
  1. If you want to use a private RPC provider,
    • Copy .env.example to init your own .env file
cp .env.example .env
  • Complete your .env file with your private settings
  1. Build project locally
yarn build

Write a Web3Function

  • Create a new file in src/web3-functions
  • Register your web3Function main function using Web3Function.onRun
  • Example:
import { Web3Function, Web3FunctionContext } from "../lib";
import { Contract } from "@ethersproject/contracts";
import ky from "ky"; // we recommend using ky as axios doesn't support fetch by default

const ORACLE_ABI = [
  "function lastUpdated() external view returns(uint256)",
  "function updatePrice(uint256)",

Web3Function.onRun(async (context: Web3FunctionContext) => {
  const { userArgs, gelatoArgs, provider } = context;

  // Retrieve Last oracle update time
  const oracleAddress = "0x6a3c82330164822A8a39C7C0224D20DB35DD030a";
  const oracle = new Contract(oracleAddress, ORACLE_ABI, provider);
  const lastUpdated = parseInt(await oracle.lastUpdated());
  console.log(`Last oracle update: ${lastUpdated}`);

  // Check if it's ready for a new update
  const nextUpdateTime = lastUpdated + 300; // 5 min
  const timestamp = (await provider.getBlock("latest")).timestamp;
  console.log(`Next oracle update: ${nextUpdateTime}`);
  if (timestamp < nextUpdateTime) {
    return { canExec: false, message: `Time not elapsed` };

  // Get current price on coingecko
  const currency = "ethereum";
  const priceData: any = await ky
      { timeout: 5_000, retry: 0 }
  price = Math.floor(priceData[currency].usd);
  console.log(`Updating price: ${price}`);

  // Return execution call data
  return {
    canExec: true,
    callData: oracle.interface.encodeFunctionData("updatePrice", [price]),
  • If your function will use Event trigger, you can get event logs from context by changing context type to Web3FunctionEventContext
import { Web3Function, Web3FunctionEventContext } from "../lib";

Web3Function.onRun(async (context: Web3FunctionEventContext) => {
  const { log } = context;

  // Retrieve event block number
  const blockNumber = log.blockNumber;
  • create your web3Function schema.json to specify your runtime configuration:
  "web3FunctionVersion": "2.0.0",
  "runtime": "js-1.0",
  "memory": 128,
  "timeout": 30,
  "userArgs": {}

Test your web3Function

  • Use yarn test FILENAME command to test your web3Function

  • Options:

    • --logs Show internal Web3Function logs
    • --runtime=thread|docker Use thread if you don't have dockerset up locally (default: thread)
    • --debug Show Runtime debug messages
    • --chain-id=[number] Specify the chainId to be used for your Web3Function (default: 11155111 sepolia)
    • --onFail Run onFail callback of the function
    • --onSuccess Run onSuccess callback of the function
  • Example: yarn test src/web3-functions/index.ts --logs --runtime=thread

  • Output:

    Web3Function Build result:
    ✓ File: ./.tmp/index.js
    ✓ File size: 1.70mb
    ✓ Build time: 109.93ms
    Web3Function running logs:
    > ChainId: 11155111
    > Last oracle update: 1665512172
    > Next oracle update: 1665512472
    > Updating price: 1586
    Web3Function Result:
    ✓ Return value: {
      canExec: true,
      callData: '0x8d6cc56d0000000000000000000000000000000000000000000000000000000000000632'
    Web3Function Runtime stats:
    ✓ Duration: 0.91s
    ✓ Memory: 57.77mb

Deploy / Fetch Web3Function

Use yarn deploy FILENAME command to upload your web3Function.

> yarn deploy ./src/web3-functions/index.ts

Use User arguments

  1. Declare your expected userArgs in you schema, accepted types are 'string', 'string[]', 'number', 'number[]', 'boolean', 'boolean[]':
  "web3FunctionVersion": "2.0.0",
  "runtime": "js-1.0",
  "memory": 128,
  "timeout": 30,
  "userArgs": {
    "currency": "string",
    "oracle": "string"
  1. Access your userArgs from the Web3Function context:
Web3Function.onRun(async (context: Web3FunctionContext) => {
  const { userArgs, gelatoArgs, secrets } = context;

  // User args:
  console.log("Currency:", userArgs.currency);
  console.log("Oracle:", userArgs.oracle);
  1. Add userArgs.json in your web3 function folder:
  "oracle": "0x6a3c82330164822A8a39C7C0224D20DB35DD030a",
  "currency": "ethereum"

Use Secrets (ie: environment variables)

Use secrets to store any private credentials that should not be published on IPFS with your web3 function.

  1. Create a .env file in your web3 function folder, containing your key / value secrets:
  1. Access your secrets from the Web3Function context:
Web3Function.onRun(async (context: Web3FunctionContext) => {
  const { secrets } = context;

  // Get api key from secrets
  const apiKey = await context.secrets.get("API_KEY");
  if (!apiKey) return { canExec: false, message: `API_KEY not set in secrets` };
  1. When creating a task on Gelato UI, you will be asked to enter secrets. They will be store securely in Gelato Network.

Use State / Storage

Web3Functions are stateless scripts, that will run in a new & empty memory context on every execution. If you need to manage some state variable, we provide a simple key/value store that you can access from your web3Function context.

See the above example to read & update values from your storage:

import {
} from "@gelatonetwork/web3-functions-sdk";

Web3Function.onRun(async (context: Web3FunctionContext) => {
  const { storage, provider } = context;

  // Use storage to retrieve previous state (stored values are always string)
  const lastBlockStr = (await storage.get("lastBlockNumber")) ?? "0";
  const lastBlock = parseInt(lastBlockStr);
  console.log(`Last block: ${lastBlock}`);

  const newBlock = await provider.getBlockNumber();
  console.log(`New block: ${newBlock}`);
  if (newBlock > lastBlock) {
    // Update storage to persist your current state (values must be cast to string)
    await storage.set("lastBlockNumber", newBlock.toString());

  return {
    canExec: false,
    message: `Updated block number: ${newBlock.toString()}`,

Test storage execution:

yarn test src/web3-functions/storage/index.ts --logs

You will see your updated key/values:

Simulated Web3Function Storage update:
 ✓ lastBlockNumber: '8321923'

To run your web3 function using mock storage values, add a storage.json in your web3 function folder:

  "lastBlockNumber": "8200000"

Use mock Event Log

To run your web3 function, that will be triggered by Events, with mock event logs, add a log.json in your web3 function folder

  "blockNumber": 10000,
  "blockHash": "0x...",
  "transactionIndex": 60,
  "removed": false,
  "address": "0x...",
  "data": "0x0...",
  "topics": [
  "transactionHash": "0x...",
  "logIndex": 0

Event Trigger Automatic Retry

If you create an event triggered web3 function, it is recommended to configure event retry in your schema.json:

  "eventRetryInterval": 60, // in seconds
  "eventRetryTtl": 3600 // in seconds

In this example, your event will be retried every 60 seconds, and will be retried for 3600 seconds (1 hour) before being discarded.

This mechanism will prevent your event response from being lost if your web3 function is failing due to external conditions like some API downtime or timeout.

Speed run DevX with the Web3 Function Hardhat Plugin

The Web3 Function Hardhat Plugin provides built-in hardhat tasks that will speed your development as well as provide a great DevX for end to end testing.

In order to user the Hardhat Plugin you will need to:

Configure Hardhat

Import Web3 functions Hardhat plugin into hardhat.config.ts:

import "@gelatonetwork/web3-functions-sdk/hardhat-plugin";

const config: HardhatUserConfig = {
  w3f: {
    rootDir: "./web3-functions", //where your Web3 Function is located
    debug: false,
    networks: ["sepolia", "baseSepolia"], //(multiChainProvider) injects provider for these networks

Web3 Function Simulation

Use the following command to run your web3 function locally:
npx hardhat w3f-run W3F_NAME

  • Options:

    • --logs Show internal Web3Function logs
  • Example:
    npx hardhat w3f-run oracle --logs

Deploy Web3 Function to IPFS

Use the following command to deploy your web3 function to IPFS:
npx hardhat w3f-deploy W3F_NAME

  • Example:
    npx hardhat w3f-deploy oracle

E2E testing

The Web3 Function hardhat plugin exposes the w3f object that can be imported directly from hardhat.

This object will help you to instantiate your Web3 Function and run it.

const { w3f } = hre;

oracleW3f = w3f.get("W3F_NAME");

userArgs = {
  currency: "ETH",
  oracleAddress: oracle.address,
let { result } = await oracleW3f.run({ userArgs });

if (result.canExec) {
  const calldata = result.callData[0];
  await owner.sendTransaction({ to: calldata.to, data: calldata.data });


Callbacks allow functions to handle status of on-chain executions, so that function state can be managed accordingly. There are two callbacks that can be provided,

[!NOTE] Callbacks are optional and their runs are accounted as normal runs, which run within plan limits.

  1. onSuccess callback invoked when on-chain execution successful

    Web3Function.onSuccess(async (context: Web3FunctionSuccessContext) => {
      const { transactionHash } = context;
      console.log("onSuccess: txHash: ", transactionHash);

    Web3FunctionSuccessContext provides the transaction hash of the on-chain execution with transactionHash.

  2. onFail callback invoked when

    • InsufficientFunds
    • SimulationFailed
    • ExecutionReverted
    Web3Function.onFail(async (context: Web3FunctionFailContext) => {
      const { reason } = context;
      if (reason === "ExecutionReverted") {
        console.log(`onFail: ${reason} txHash: ${context.transactionHash}`);
      } else if (reason === "SimulationFailed") {
          `onFail: ${reason} callData: ${JSON.stringify(context.callData)}`
      } else {
        console.log(`onFail: ${reason}`);

    Web3FunctionFailContext provides reason of the failure with reason and additional data;

    • SimulationFailed

      Call data provided during function run with callData

    • ExecutionReverted

      transaction hash of the reverted on-chain execution with transactionHash

Testing callbacks

Provide --onFail or --onSuccess flags to test command to test onFail or onSuccess callbacks respectively, example;

$> yarn test src/web3-functions/callbacks/index.ts --logs --runtime=thread --onFail

    Web3Function Build result:
    ✓ Schema: src/web3-functions/callbacks/schema.json
    ✓ Built file: ./.tmp/index.js
    ✓ File size: 0.58mb
    ✓ Build time: 75.25ms

    Web3Function user args validation:
    ✓ canExec: false

    Web3Function running logs:
    > userArgs:  false
    > onFail: SimulationFailed callData: [{"to":"0x0000000000000000000000000000000000000000","data":"0x00000000"}]

    Web3Function onFail result:
    ✓ Success

    Web3Function Runtime stats:
    ✓ Duration: 0.23s
    ✓ Memory: 61.06mb
    ✓ Storage: 0.04kb
    ✓ Network: 0 req [ DL: 0.00kb / UL:  0.00kb]
    ✓ Rpc calls: 0
    ✨  Done in 2.03s.

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