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Web3 Functions Template

Use this template to write, test and deploy Web3 Functions.

What are Web3 Functions?

Web3 Functions are decentralized cloud functions that work similarly to AWS Lambda or Google Cloud, just for web3. They enable developers to execute on-chain transactions based on arbitrary off-chain data (APIs / subgraphs, etc) & computation. These functions are written in Typescript, stored on IPFS and run by Gelato.

Documentation

You can find the official Web3 Functions documentation here.

Private Beta Restriction

Web3 Functions are currently in private Beta and can only be used by whitelisted users. If you would like to be added to the waitlist, please reach out to the team on Discord or apply using this form.

Table of Content

Project Setup

  1. Install project dependencies
yarn install
  1. Configure your local environment:
  • Copy .env.example to init your own .env file
cp .env.example .env
  • Complete your .env file with your private settings
ALCHEMY_ID=
INFURA_ID=
PRIVATE_KEY=

Hardhat Config

In hardhat.config.ts, you can set up configurations for your Web3 Function runtime.

  • rootDir: Directory which contains all web3 functions directories.
  • debug: Run your web3 functions with debug mode on.
  • networks: Provider of these networks will be injected into web3 function's multi chain provider.
  w3f: {
    rootDir: "./web3-functions",
    debug: false,
    networks: ["ethereum", "sepolia", "polygon", "hardhat", "amoy"],
  },

Write a Web3 Function

  • Go to web3-functions/index.ts
  • Write your Web3 Function logic within the Web3Function.onRun function.
  • Example:
import {
  Web3Function,
  Web3FunctionContext,
} from "@gelatonetwork/web3-functions-sdk";
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, multiChainProvider } = context;

  const provider = multiChainProvider.default();

  // Retrieve Last oracle update time
  const oracleAddress = "0x71B9B0F6C999CBbB0FeF9c92B80D54e4973214da";
  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
    .get(
      `https://api.coingecko.com/api/v3/simple/price?ids=${currency}&vs_currencies=usd`,
      { timeout: 5_000, retry: 0 }
    )
    .json();
  price = Math.floor(priceData[currency].usd);
  console.log(`Updating price: ${price}`);

  // Return execution call data
  return {
    canExec: true,
    callData: [{to: oracleAddress, data: oracle.interface.encodeFunctionData("updatePrice", [price])}],
  };
});
  • Each Web3 Function has a schema.json file to specify the runtime configuration. In later versions you will have more optionality to define what resources your Web3 Function requires.
{
  "web3FunctionVersion": "2.0.0",
  "runtime": "js-1.0",
  "memory": 128,
  "timeout": 30,
  "userArgs": {}
}

Test your web3 function

Calling your web3 function

  • Use npx hardhat w3f-run W3FNAME command to test your function (replace W3FNAME with the folder name containing your web3 function)

  • Options:

    • --logs Show internal Web3 Function logs
    • --debug Show Runtime debug messages
    • --network [NETWORK] Set the default runtime network & provider.

If your web3 function has arguments, you can define them in hardhat.config.ts.

Example:
npx hardhat w3f-run oracle --logs

Output:

Web3Function building...

Web3Function Build result:
✓ Schema: web3-functions/examples/oracle/schema.json
✓ Built file: ./.tmp/index.js
✓ File size: 2.46mb
✓ Build time: 255.66ms

Web3Function user args validation:
✓ currency: ethereum
✓ oracle: 0x71B9B0F6C999CBbB0FeF9c92B80D54e4973214da

Web3Function running...

Web3Function Result:
✓ Return value: { canExec: false, message: 'Rpc call failed' }

Web3Function Runtime stats:
✓ Duration: 0.41s
✓ Memory: 65.65mb
✓ Rpc calls: 2

Writing unit test for your web3 function

  • Define your tests in test/index.test.ts
  • Use yarn test command to run unit test suite.

Hardhat will run your tests in a forked environment by default. You can configure this in hardhat.config.ts.

{
  defaultNetwork: "hardhat",

  networks: {
    hardhat: {
      chainId: 31337,
      forking: {
        url: `https://polygon-amoy.g.alchemy.com/v2/${ALCHEMY_ID}`,
        blockNumber: 4628220,
      },
    },
  }
}

w3f class is injected into the hardhat runtime environment.


Calling your web3 function: 
import hre from "hardhat";
const { w3f } = hre;

const oracleW3f = w3f.get("oracle");

const userArgs = {
  currency: "ethereum",
  oracle: oracle.address,
};

const storage = {};

await oracleW3f.run({storage, userArgs});

userArgs and storage are optional here. When passed, it overrides the arguments defined in userArgs.json and storage.json.

Use User arguments

  1. Declare your expected userArgs in your 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. Populate userArgs in userArgs.json and test your web3 function:
{
  "currency": "ethereum",
  "oracle": "0x71B9B0F6C999CBbB0FeF9c92B80D54e4973214da"
}

npx hardhat w3f-run oracle --logs

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 web3 function context.

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

import {
  Web3Function,
  Web3FunctionContext,
} from "@gelatonetwork/web3-functions-sdk";

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

  const provider = multiChainProvider.default();

  // 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:
npx hardhat w3f-run storage --logs

You will see your updated key/values:

Simulated Web3Function Storage update:
 ✓ lastBlockNumber: '8944652'

Use user secrets

  1. Input your secrets in .env file in the same directory as your web3 function.
COINGECKO_API=https://api.coingecko.com/api/v3
  1. Access your secrets from the Web3Function context:
// Get api from secrets
const coingeckoApi = await context.secrets.get("COINGECKO_API");
if (!coingeckoApi)
  return { canExec: false, message: `COINGECKO_API not set in secrets` };
  1. Test your Web3 Function using secrets:
    npx hardhat w3f-run secrets --logs

Deploy your Web3Function on IPFS

Use npx hardhat w3f-deploy W3FNAME command to deploy your web3 function.

Example:
npx hardhat w3f-deploy oracle

The deployer will output your Web3Function IPFS CID, that you can use to create your task:

 ✓ Web3Function deployed to ipfs.
 ✓ CID: Qmbykp8botbdzjX9YEoc14VnC3eeaZoJ4EGzak5KzstRqH

To create a task that runs your Web3 Function every minute, visit:
> https://beta.app.gelato.network/new-task?cid=Qmbykp8botbdzjX9YEoc14VnC3eeaZoJ4EGzak5KzstRqH

Create your Web3Function task

Use the automate-sdk to easily create a new task (make sure you have your private_key in .env):

const { taskId, tx } = await automate.createBatchExecTask({
  name: "Web3Function - Eth Oracle",
  web3FunctionHash: cid,
  web3FunctionArgs: {
    oracle: oracle.address,
    currency: "ethereum",
  },
});
await tx.wait();

If your task utilizes secrets, you can set them after the task has been created.

// Set task specific secrets
const secrets = oracleW3f.getSecrets();
if (Object.keys(secrets).length > 0) {
  await web3Function.secrets.set(secrets, taskId);
  console.log(`Secrets set`);
}

Test it with our sample task creation script:
yarn create-task:oracle

Deploying Web3Function on IPFS...
Web3Function IPFS CID: QmVfDbGGN6qfPs5ocu2ZuzLdBsXpu7zdfPwh14LwFUHLnc

Creating automate task...
Task created, taskId: 0x8438933eb9c6e4632d984b4db1e7672082d367b900e536f86295b2e23dbcaff3
> https://beta.app.gelato.network/task/0x8438933eb9c6e4632d984b4db1e7672082d367b900e536f86295b2e23dbcaff3?chainId=5

More examples

Coingecko oracle

Fetch price data from Coingecko API to update your on-chain Oracle

Source: web3-functions/examples/oracle/index.ts

Run:
npx hardhat w3f-run oracle --logs

Create task:
yarn create-task:oracle

Event listener

Listen to smart contract events and use storage context to maintain your execution state.

Source: web3-functions/examples/event-listener/index.ts

Run:
npx hardhat w3f-run event --logs

Secrets

Fetch data from a private API to update your on-chain Oracle

Source: web3-functions/examples/secrets/index.ts

Run:
npx hardhat w3f-run secrets --logs

Advertising Board

Fetch a random quote from an API and post it on chain.

Source: web3-functions/examples/advertising-board/index.ts

Run:
npx hardhat w3f-run adboard

Create task:
yarn create-task:adboard