Substrate Validator Set Pallet

A Substrate pallet to add/remove authorities/validators using extrinsics, in Substrate-based PoA networks.

Note: Current master is compatible with Substrate monthly-2021-10 tag. For older versions, please see releases/tags.

Demo

To see this pallet in action in a Substrate runtime, watch this video - https://www.youtube.com/watch?v=lIYxE-tOAdw

Setup with Substrate Node Template

Add the module's dependency in the Cargo.toml of your runtime directory. Make sure to enter the correct path or git url of the pallet as per your setup.
Make sure that you also have the Substrate session pallet as part of your runtime. This is because the validator-set pallet is dependent on the session pallet.

[dependencies.validator-set]
default-features = false
package = 'substrate-validator-set'
git = 'https://github.com/gautamdhameja/substrate-validator-set.git'
version = '4.0.0-dev'

[dependencies.pallet-session]
default-features = false
git = 'https://github.com/paritytech/substrate.git'
tag = 'monthly-2021-09+1'
version = '4.0.0-dev'

std = [
	...
	'validator-set/std',
	'pallet-session/std',
]

Import OpaqueKeys in your runtime/src/lib.rs.

use sp_runtime::traits::{
	AccountIdLookup, BlakeTwo256, Block as BlockT, Verify, IdentifyAccount, NumberFor, OpaqueKeys
};

Also in runtime/src/lib.rs import the EnsureRoot trait. This would change if you want to configure a custom origin (see below).

	use frame_system::EnsureRoot;

Declare the pallet in your runtime/src/lib.rs. The pallet supports configurable origin and you can either set it to use one of the governance pallets (Collective, Democracy, etc.), or just use root as shown below. But do not use a normal origin here because the addition and removal of validators should be done using elevated privileges.

impl validator_set::Config for Runtime {
	type Event = Event;
	type AddRemoveOrigin = EnsureRoot<AccountId>;
}

Also, declare the session pallet in your runtime/src/lib.rs. The type configuration of session pallet would depend on the ValidatorSet pallet as shown below.

parameter_types! {
	pub const Period: u32 = 2 * MINUTES;
	pub const Offset: u32 = 0;
}

impl pallet_session::Config for Runtime {
	type SessionHandler = <opaque::SessionKeys as OpaqueKeys>::KeyTypeIdProviders;
	type ShouldEndSession = pallet_session::PeriodicSessions<Period, Offset>;
	type NextSessionRotation = pallet_session::PeriodicSessions<Period, Offset>;
	type SessionManager = ValidatorSet;
	type Event = Event;
	type Keys = opaque::SessionKeys;
	type ValidatorId = <Self as frame_system::Config>::AccountId;
	type ValidatorIdOf = validator_set::ValidatorOf<Self>;
	type DisabledValidatorsThreshold = ();
	type WeightInfo = ();
}

Add both session and validator_set pallets in construct_runtime macro. Make sure to add them before Aura and Grandpa pallets and after Balances.

construct_runtime!(
	pub enum Runtime where
		Block = Block,
		NodeBlock = opaque::Block,
		UncheckedExtrinsic = UncheckedExtrinsic
	{
		...
		Balances: pallet_balances::{Pallet, Call, Storage, Config<T>, Event<T>},
		Session: pallet_session::{Pallet, Call, Storage, Event, Config<T>},
		ValidatorSet: validator_set::{Pallet, Call, Storage, Event<T>, Config<T>},
		Aura: pallet_aura::{Pallet, Config<T>},
		Grandpa: pallet_grandpa::{Pallet, Call, Storage, Config, Event},
		...
		...
	}
);

Add genesis config in the chain_spec.rs file for session and validatorset pallets, and update it for Aura and Grandpa pallets. Because the validators are provided by the session pallet, we do not initialize them explicitly for Aura and Grandpa pallets. Order is important, notice that pallet_session is declared after pallet_balances since it depends on it (session accounts should have some balance).

fn testnet_genesis(initial_authorities: Vec<(AccountId, AuraId, GrandpaId)>,
	root_key: AccountId,
	endowed_accounts: Vec<AccountId>,
	_enable_println: bool) -> GenesisConfig {
	GenesisConfig {
		...,
		balances: BalancesConfig {
			balances: endowed_accounts.iter().cloned().map(|k|(k, 1 << 60)).collect(),
		},
		validator_set: ValidatorSetConfig {
			validators: initial_authorities.iter().map(|x| x.0.clone()).collect::<Vec<_>>(),
		},
		session: SessionConfig {
			keys: initial_authorities.iter().map(|x| {
				(x.0.clone(), x.0.clone(), session_keys(x.1.clone(), x.2.clone()))
			}).collect::<Vec<_>>(),
		},
		aura: AuraConfig {
			authorities: vec![],
		},
		grandpa: GrandpaConfig {
			authorities: vec![],
		},
	}
}

Make sure you have the same number and order of session keys for your runtime. First in runtime/src/lib.rs:

pub struct SessionKeys {
	pub aura: Aura,
	pub grandpa: Grandpa,
}

And then in node/src/chain_spec.rs:

fn session_keys(
	aura: AuraId,
	grandpa: GrandpaId,
) -> SessionKeys {
	SessionKeys { aura, grandpa }
}

pub fn authority_keys_from_seed(s: &str) -> (
	AccountId,
	AuraId,
	GrandpaId
) {
	(
		get_account_id_from_seed::<sr25519::Public>(s),
		get_from_seed::<AuraId>(s),
		get_from_seed::<GrandpaId>(s)
	)
}

Import opaque::SessionKeys, ValidatorSetConfig, SessionConfig from the runtime in node/src/chain_spec.rs.

use node_template_runtime::{
	AccountId, AuraConfig, BalancesConfig, GenesisConfig, GrandpaConfig,
	SudoConfig, SystemConfig, WASM_BINARY, Signature, 
	opaque::SessionKeys, ValidatorSetConfig, SessionConfig
};

Run

Once you have set up the pallet in your node/node-template and everything compiles, watch this video to see how to run the chain and add validators - https://www.youtube.com/watch?v=lIYxE-tOAdw.

To use the pallet with the Collective pallet, follow the steps in docs/council-integration.md.

Types for Polkadot JS Apps/API

{
  "Keys": "SessionKeys2"
}

Disclaimer

This code not audited and reviewed for production use cases. You can expect bugs and security vulnerabilities. Do not use it as-is in real applications.

riusricardo/substrate-validator-set

Substrate Validator Set Pallet

Demo

Setup with Substrate Node Template

Run

Types for Polkadot JS Apps/API

Disclaimer