This package is part of ChainSafe's Lodestar project

Lodestar defines all network configuration variables defined in the Ethereum Consensus spec. This tooling may be used to configure testnets, ingest mainnet/testnet config variables, or be used in downstream Lodestar libraries.

npm install @lodestar/config

The Lodestar config package contains several interfaces used in downstream Lodestar libraries:

• ChainConfig - Typescript interface, Default (mainnet) values, and matching SSZ helper type object
• ForkConfig - A fork helper object that's structured around the fork schedule
• ChainForkConfig A wrapper object that implements ChainConfig and ForkConfig
• CachedGenesis - A helper object for caching domains (which relies on the genesis validators root)
• BeaconConfig - A wrapper object that implements all above interfaces

The Ethereum consensus spec defines a bunch of variables that may be easily configured per testnet. These include the GENESIS_TIME, SECONDS_PER_SLOT, and various *_FORK_EPOCHs, *_FORK_VERSIONs, etc. The Lodestar config package exports the ChainConfig interface and matching ChainConfig SSZ type, which include all of these variables, named verbatim from the spec.

import {ChainConfig} from "@lodestar/config";
import {chainConfig} from "@lodestar/config/default";

let config: ChainConfig = chainConfig;
const x: number = config.SECONDS_PER_SLOT;

Mainnet default values are available as a singleton ChainConfig under the default import path.

import {chainConfig} from "@lodestar/config/default";

chainConfig.SECONDS_PER_SLOT === 12;

There are also utility functions to help create a ChainConfig from unknown input and partial configs.

import {createChainConfig, ChainConfig, chainConfigFromJson} from "@lodestar/config";

// example config
let chainConfigObj: Record<string, unknown> = {
  // phase0
  MIN_PER_EPOCH_CHURN_LIMIT: 4,
  CHURN_LIMIT_QUOTIENT: 65536,
  MIN_GENESIS_ACTIVE_VALIDATOR_COUNT: 128,
  MIN_GENESIS_TIME: 1621504614,
  ETH1_FOLLOW_DISTANCE: 2048,
  SECONDS_PER_ETH1_BLOCK: 14,
  DEPOSIT_CHAIN_ID: 5,
  DEPOSIT_NETWORK_ID: 5,
  DEPOSIT_CONTRACT_ADDRESS: "0x2cc88381fe23027743c1f85512bffb383acca7c7",
  EJECTION_BALANCE: 16000000000,
  GENESIS_FORK_VERSION: "0x00004811",
  GENESIS_DELAY: 1100642,
  SECONDS_PER_SLOT: 12,
  MIN_VALIDATOR_WITHDRAWABILITY_DELAY: 256,
  SHARD_COMMITTEE_PERIOD: 256,

  // altair
  INACTIVITY_SCORE_BIAS: 4,
  INACTIVITY_SCORE_RECOVERY_RATE: 16,
  ALTAIR_FORK_VERSION: "0x01004811",
  ALTAIR_FORK_EPOCH: 10,
};

const partialChainConfig: Partial<ChainConfig> = chainConfigFromJson(chainConfigObj);

// Fill in the missing values with mainnet default values
const chainConfig: ChainConfig = createChainConfig(partialChainConfig);

The variables described in the spec can be used to assemble a more structured 'fork schedule'. This info is organized as ForkConfig in the Lodestar config package. In practice, the ChainConfig and ForkConfig are usually combined as a ChainForkConfig.

A ForkConfig provides methods to select the fork info, fork name, fork version, or fork ssz types given a slot.

import {GENESIS_SLOT} from "@lodestar/params";
import {createChainForkConfig, ChainForkConfig} from "@lodestar/config";
import {config as chainConfig} from "@lodestar/config/default";

const config: ChainForkConfig = createChainForkConfig(chainConfig);

const version = config.getForkVersion(GENESIS_SLOT);

For signing Ethereum consensus objects, a cryptographic "domain" is computed and mixed into the signed message. This domain separates signatures made for the Ethereum mainnet from testnets or other instances of the chain. The CachedGenesis interface is used to provide a cache for this purpose. Practically, the domain rarely changes, only per-fork, and so the value can be easily cached. Since the genesis validators root is part of the domain, it is required input to instantiate an CachedGenesis. In practice, the ChainForkConfig and CachedGenesis are usually combined as a BeaconConfig. This is the 'highest level' object exported by the Lodestar config library.

import {DOMAIN_DEPOSIT, GENESIS_SLOT} from "@lodestar/params";
import {createBeaconConfig, BeaconConfig} from "@lodestar/config";
import {config as chainConfig} from "@lodestar/config/default";

// dummy test root
let genesisValidatorsRoot: Uint8Array = new Uint8Array();

const config: BeaconConfig = createBeaconConfig(chainConfig, genesisValidatorsRoot);

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