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

UNDER CONSTRUCTION

This document is under construction and may change significantly as we incorporate style guidance and feedback from readers. Feel free to request specific clarifications by clicking the Request an update button at the top of this document.

info

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

This guide will help you configure and deploy a custom gas token Orbit chain.

Custom gas token orbit chains let participants pay transaction fees in ERC-20 token instead of ETH, which is ideal for use cases requiring this feature and low transaction fees. You can learn more on our page covering custom gas token requirements and configuration.

Deploying a custom gas token Orbit chain is similar to deploying an AnyTrust Orbit chain but with additional steps. To take advantage of all the chains configurations supported by Orbit, we recommend reading our short guides about Rollup and AnyTrust configuration.

note
  • Custom gas tokens are not supported yet on Rollup Orbit chains, only on Orbit AnyTrust chains.
  • ERC-20 tokens need 18 decimals to operate as gas tokens on Orbit chains.

1. Custom gas token specification

The difference between custom gas token chains and other Orbit chains is the use of an ERC-20 token as the gas token. Enabling this feature requires that you select an existing ERC-20 token or deploy a new one on the parent chain.

2. Chain configuration

Chain configuration is the same as for any other AnyTrust chain. See more here.

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 token Allowance from the owner:

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

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

const enoughAllowance = await createRollupEnoughCustomFeeTokenAllowance(allowanceParams);

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

ParameterTypeDescription
nativeTokenAddressThe contract address on the parent chain of the ERC-20 token your chain will use for gas fees.
accountAddressThe address of the Orbit chain's deployer.
publicClientPublicClientThe 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 createRollupPrepareDeploymentParamsConfig and createRollupPrepareTransactionRequest, remains similar to the AnyTrust 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,
batchPosters: [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.