Writing Typescript Functions
1) Install dependencies
npm install @gelatonetwork/web3-functions-sdk
or use the template on Github's UI.
2) Fill in your provider rpc url & private key
Note: PRIVATE_KEY
is optional, and only needed if you wish to deploy contracts or create a task from the CLI instead of the UI
// .env file
RPOVIDER_URLS= // <= Your Provider rpc url
PRIVATE_KEY= // <= Your Private key
Typescript Function Example
This typescript function updates an oracle smart contract with data returned by Coingecko's price API at an interval. Check out more examples here.
import { Web3Function, Web3FunctionContext } from "@gelatonetwork/web3-functions-sdk";
import { Contract, ethers } from "ethers";
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])
}],
};
});
Create your function schema.json
to specify your runtime configuration.
{
"web3FunctionVersion": "2.0.0",
"runtime": "js-1.0",
"memory": 128,
"timeout": 30,
"userArgs": {}
}
Note: For now the configuration is fixed and cannot be changed.
Typescript Function Context
When writing the Web3 Function, it is very helpful to understand the context Gelato injects into the execution, providing additional features to widen the Web3 Functions applicability.
Web3Function.onRun(async (context: Web3FunctionContext) => {
const { userArgs, storage, secrets, multiChainProvider, gelatoArgs} = context;
const provider = multiChainProvider.default();
...
}
User Arguments
Declare your expected
userArgs
in your schema.json, accepted types arestring
,string[]
,number
,number[]
,boolean
,boolean[]
:
{
"web3FunctionVersion": "2.0.0",
"runtime": "js-1.0",
"memory": 128,
"timeout": 30,
"userArgs": {
"currency": "string",
"oracle": "string"
}
}
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)
...
});
In the same directory as your web3 function, create a file
userArgs.json
and fill in youruserArgs
to test your web3 function:
{
"currency": "ethereum",
"oracle": "0x71B9B0F6C999CBbB0FeF9c92B80D54e4973214da"
}
Test out the Coingecko oracle web3 function:
npx w3f test path/to/web3-functions/oracle/index.ts --logs
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 above 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()}`,
};
});
To populate the storage values in your testing, in the same directory as your web3 function, create a file storage.json
and fill in the storage values.
{
"lastBlockNumber": "1000"
}
Test out the storage web3 function:
npx w3f test path/to/web3-functions/storage/index.ts --logs
Secrets
In the same directory as your web3 function, create a
.env
file and fill up your secrets.
COINGECKO_API=https://api.coingecko.com/api/v3
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` };
}
Test your web3 function using secrets:
npx w3f test path/to/web3-functions/secrets/index.ts --logs
When deploying a task, you will be able to set your web3 function secrets on our UI or using the SDK, see here
import hre from "hardhat";
import { AutomateSDK, Web3Function } from "@gelatonetwork/automate-sdk";
const { ethers, w3f } = hre;
const adBoardW3f = w3f.get("advertising-board");
const [deployer] = await ethers.getSigners();
const chainId = (await ethers.provider.getNetwork()).chainId;
const automate = new AutomateSDK(chainId, deployer);
const web3Function = new Web3Function(chainId, deployer);
// Deploy Web3Function on IPFS
console.log("Deploying Web3Function on IPFS...");
const cid = await adBoardW3f.deploy();
console.log(`Web3Function IPFS CID: ${cid}`);
// Create task using automate sdk
console.log("Creating automate task...");
const { taskId, tx } = await automate.createBatchExecTask({
name: "Web3Function - Ad Board",
web3FunctionHash: cid,
web3FunctionArgs: {},
});
await tx.wait();
console.log(`Task created, taskId: ${taskId} (tx hash: ${tx.hash})`);
console.log(
`> https://beta.app.gelato.network/task/${taskId}?chainId=${chainId}`
);
// Set task specific secrets
const secrets = adBoardW3f.getSecrets();
if (Object.keys(secrets).length > 0) {
await web3Function.secrets.set(secrets, taskId);
console.log(`Secrets set`);
}
Multichain Provider
The multichainProvider
allows us to instantiate RPC providers for every network Gelato is deployed on.
import {
Web3Function,
Web3FunctionContext,
} from "@gelatonetwork/web3-functions-sdk";
Web3Function.onRun(async (context: Web3FunctionContext) => {
const { multiChainProvider } = context;
// multichainProvider.default() will instantiate
// the provider of the chain the W3F is deployed
const provider = multiChainProvider.default();
// passing the chainId as follows, we can instantiate
// a rpc provider for that network
const polygonProvider = multiChainProvider.chainId(137)
...
// This method fetches the number of remaining RPC calls,
// allowing dynamic adaptations based on the user's plan limits.
const remainingCalls = await multiChainProvider.nbRpcCallsRemaining();
...
}
When testing locally, we can provide the different providers by including them in .env
at the root folder.
// .env file
PROVIDER_URLS=RPC1,RPC2
Interoperability with Other Libraries
Although multiChainProvider
is designed to work seamlessly within the Gelato Web3 Functions SDK, it is possible to extract the underlying RPC URL and use it with other client libraries. This flexibility is valuable for developers who prefer or require features from other libraries, such as viem
.
Here's an example of how to utilize the RPC URL from multiChainProvider
with the viem
library, which can be useful if you need to leverage features specific to viem
:
import { createPublicClient, http } from "viem";
import { polygon } from "viem/chains";
Web3Function.onRun(async (context: Web3FunctionContext) => {
const { multiChainProvider } = context;
const provider = multiChainProvider.default();
const url = provider.connection.url;
// Initialize viem client with the extracted URL
const rpc = createPublicClient({
chain: polygon,
transport: http(url),
});
// Now you can use the viem client for your operations
// ...
});
Gelato Arguments
Gelato injects the chainId
, the gasPrice
, and the taskId
into the context.
chainId: The unique number identifying the blockchain network where the function is running.
gasPrice: The cost of executing transactions on the blockchain.
taskId: A string that uniquely identifies the task.
import {
Web3Function,
Web3FunctionContext,
} from "@gelatonetwork/web3-functions-sdk";
Web3Function.onRun(async (context: Web3FunctionContext) => {
const { gelatoArgs } = context;
// chainId: number
const chainId = gelatoArgs.chainId;
// gasPrice: BigNumber
const gasPrice = gelatoArgs.gasPrice;
// taskId: string
const taskId = gelatoArgs.taskId;
...
}
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