How to deploy a custom gas token chain using the Orbit SDK

UNDER CONSTRUCTION

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info

See the "create a rollup custom fee token" example in the Orbit SDK repository for additional guidance.

Deploying a Custom Gas Token Orbit chain introduces a unique aspect to the standard Orbit chain setup: the ability to pay transaction fees using a specific ERC-20 token instead of ETH. While the setup process largely mirrors that of a standard Rollup Orbit chain, as detailed in the introduction, there are key differences to account for when configuring a Custom Gas Token Orbit chain.

info

Custom gas tokens are only supported on Orbit AnyTrust chains, currently. This feature is not available yet on Rollup Orbit chains.

Key Differences for Custom Gas Token Orbit Chain Deployment

1. Custom gas token specification

The most significant difference is the specification of the ERC-20 token on the parent chain to be used as the gas fee token. This requires selecting an existing ERC-20 token or deploying a new one to be used specifically for transaction fees on your Orbit chain.

Note: Currently, only ERC-20 tokens with 18 decimals are acceptable as gas tokens on Orbit chains.

2. Chain Configuration

You can configure your Orbit chain using the prepareChainConfig method and assigning it to a chainConfig variable.

Example:

import { prepareChainConfig } from '@arbitrum/orbit-sdk';

const chainConfig = prepareChainConfig({
    chainId: Some_Chain_ID,
    nativeToken: yourERC-20TokenAddress,
    DataAvailabilityCommittee: true,
});

To use the prepareChainConfig method as shown in the example above, some inputs need to be defined:

Parameter	Type	Description
chainId	number	Your Orbit chain's chainId.
nativeToken	Address	The contract address on the parent chain of the ERC-20 token your chain will use for gas fees. It needs to have 18 decimals to be accepted on Orbit chains.
DataAvailabilityCommittee	boolean	Should be set to true since only AnyTrust chains can accept ERC-20 tokens.

3. Token Approval Before Deployment Process

In Custom gas token Orbit chains, the owner needs to give allowance to the rollupCreator contract before starting the deployment process so that RollupCreator can spend enough tokens for the deployment process. For this purpose, we defined two APIs on the Orbit SDK:

A. createRollupEnoughCustomFeeTokenAllowance

This API gets related inputs and checks if the rollupCreator contract has enough Allowance on the token from the owner:

import {createRollupEnoughCustomFeeTokenAllowance} from '@arbitrum/orbit-sdk';

const allowanceParams = {
nativeToken,
account: deployer.address,
publicClient: parentChainPublicClient,
};

const enough Allowance = createRollupEnoughCustomFeeTokenAllowance(allowanceParams)

To build the allowanceParams object as shown in the example above, you need to provide with the following:

Parameter	Type	Description
nativeToken	Address	The contract address on the parent chain of the ERC-20 token your chain will use for gas fees.
account	Address	The address Orbit chain's
publicClient	PublicClient	The PublicClient object as defined by the Viem library.

B. createRollupPrepareCustomFeeTokenApprovalTransactionRequest

This API gets related inputs and creates the transaction request to secure enough Allowance from the owner to the RollupCreator to spend nativeToken on the deployment process.

Example:

import { createRollupEnoughCustomFeeTokenAllowance } from '@arbitrum/orbit-sdk';

const allowanceParams = {
  nativeToken,
  account: deployer.address,
  publicClient: parentChainPublicClient,
};

const approvalTxRequest = await createRollupPrepareCustomFeeTokenApprovalTransactionRequest(
  allowanceParams,
);

4. Deployment Process

The overall deployment process, including the use of APIs like createRollupPrepareConfig and createRollupPrepareTransactionRequest, remains similar to the Rollup deployment process. However, attention must be given to incorporating the ERC-20 token details into these configurations.

note

When using the API, you also need to specify nativeToken as a param.

Example:

const txRequest = await createRollupPrepareTransactionRequest({
  params: {
    config,
    batchPoster,
    validators: [validator],
    nativeToken,
  },
  account: deployer.address,
  publicClient: parentChainPublicClient,
});

All other parts would be the same as explained in the Rollup Orbit chain deployment page.