How to configure your Arbitrum chain's node using the Arbitrum chain (Orbit) SDK

This guide will walk you through configuring an Arbitrum chain node supporting a Rollup or AnyTrust chain.

UNDER CONSTRUCTION

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info

See the "prepare-node-config" example in the Arbitrum chain (Orbit) SDK repository for additional guidance.

• Prerequisite: having deployed an Arbitrum chain. If you haven't done so yet, you can find detailed instructions in the Rollup Deployment Parameters section of the rollup deployment guide.

Once you have successfully deployed and initialized the Arbitrum chain core contracts, the next step is configuring and running your Arbitrum chain using a Node Config JSON file describing all the configurations for the Arbitrum Node, including settings for the Batch-poster, Validator, and the chain itself.

Example for a Rollup Arbitrum Chain:

{
  'chain': {
    'info-json': stringifyInfoJson([...]),
    'name': chainName,
    // Additional chain-specific configurations
  },
  'parent-chain': {
    connection: {
      url: parentChainRpcUrl,
    },
  },
  'http': {
    addr: '0.0.0.0',
    port: 8449,
    vhosts: '*',
    corsdomain: '*',
    api: ['eth', 'net', 'web3', 'arb', 'debug'],
  },
  'node': {
    // Node-specific settings including sequencer, batch-poster, staker configurations
  },
};

Here are some inputs details from the example above:

Parameters	Description
chain	Details about the hosted chain, including chain ID, name, and core contracts.
parent-chain	Information for connecting to the parent chain.
http	Configuration parameters for the HTTP server.
node	Specific node settings, including sequencer and batch-poster configurations.

Additional configuration for AnyTrust Arbitrum chains:

For AnyTrust Arbitrum chains, the Node Config JSON has an additional segment under the node field. This addition includes settings specific to the AnyTrust model, such as:

• Sequencer's inbox address
• Parent chain node URL
• RPC aggregators

Example addition for AnyTrust Node Config:

{
  ...
  'node': {
    ...
    'sequencer-inbox-address': coreContracts.sequencerInbox,
    'parent-chain-node-url': parentChainRpcUrl,
    'rest-aggregator': {
      enable: true,
      urls: 'http://localhost:9876',
    },
    'rpc-aggregator': {
      'enable': true,
      'assumed-honest': 1,
      'backends': stringifyBackendsJson([...]),
    },
  }
  ...
};

Preparing your node config file

The Node Config file includes three fields types:

1. Information from the Arbitrum deployment chain: Such as the addresses of the core contracts.
2. Parameters configurable by the chain deployer: These parameters, like max-block-speed, can be adjusted to modify your chain's behavior.
3. Fields not typically configured: Like the HTTP section, which usually remains standard.

Let's explore the parameters allowing you to set up a stable, and secure Arbitrum chain tailored to your project's requirements:

Node config generation with Arbitrum chain (Orbit) SDK

Generating a Node Config JSON file to initiate your Arbitrum chain is a step in the deployment process. The Arbitrum chain (Orbit) SDK simplifies this task with an API named prepareNodeConfig. This API takes specific parameters for your Arbitrum chain and returns a JSON file that can be used as the Node Config to initiate the chain.

Here’s an example of using the prepareNodeConfig API to generate the node config:

const nodeConfig = prepareNodeConfig({
  chainName: 'My Orbit Chain',
  chainConfig,
  coreContracts,
  batchPosterPrivateKey: 'BATCH_POSTER_PRIVATE_KEY_HERE',
  validatorPrivateKey: 'VALIDATOR_PRIVATE_KEY_HERE',
  parentChainId: parentChain_chain_id,
  parentChainRpcUrl: parentChain_RPC_URL,
});

Here are some details about the parameters used in the example above:

Parameters	Description
chainName	The name you have chosen for your Arbitrum chain.
chainConfig	Configuration used for chain deployment, returned from the createRollupPrepareTransactionReceipt API.
coreContracts	Addresses of your newly deployed Arbitrum chain's, also returned from the createRollupPrepareTransactionReceipt API.
batchPosterPrivateKey	Private key of the batch-poster account, used for signing batch-posting transactions and related functions.
validatorPrivateKey	Private key of the validator(s), used for validating state, posting assertions (RBlocks) to the parent chain, and initiating challenges if necessary.
parentChainId	Chain ID of the parent chain where your Arbitrum chain is deployed.
parentChainRpcUrl	Parent chain's RPC URL.

If you don't have the chainConfig and coreContracts readily available, you can obtain them using the createRollupPrepareTransaction and createRollupPrepareTransactionReceipt APIs.

Here's an example of how to extract chainConfig and coreContracts using just the transaction hash from your deployment:

import {
  ChainConfig,
  createRollupPrepareTransaction,
  createRollupPrepareTransactionReceipt,
} from '@arbitrum/orbit-sdk';

const tx = createRollupPrepareTransaction({ hash: txHash });
const txReceipt = createRollupPrepareTransactionReceipt({ hash: txHash });
const chainConfig: ChainConfig = JSON.parse(tx.getInputs()[0].config.chainConfig);
const coreContracts = txReceipt.getCoreContracts();

This process ensures that all necessary configurations and contract details are included in your Node Config.