This video demonstrates how to add a new validator in a Substrate PoA network using the ValidatorSet pallet.

Substrate Validator Set

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

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.

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

• Make sure that you also have the Substrate session pallet as part of your runtime. This is because the validator-set pallet is based on the session pallet.

• Declare the pallet in your runtime/src/lib.rs.

pub use validatorset;

impl validatorset::Trait for Runtime {
	type Event = Event;
}

• 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.

impl session::Trait for Runtime {
	type SessionHandler = <opaque::SessionKeys as OpaqueKeys>::KeyTypeIdProviders;
	type ShouldEndSession = ValidatorSet;
	type SessionManager = ValidatorSet;
	type Event = Event;
	type Keys = opaque::SessionKeys;
	type NextSessionRotation = ValidatorSet;
	type ValidatorId = <Self as system::Trait>::AccountId;
	type ValidatorIdOf = validatorset::ValidatorOf<Self>;
	type DisabledValidatorsThreshold = ();
}

• Add both session and validatorset pallets in construct_runtime macro. Make sure to add them before Aura and Grandpa pallets.

construct_runtime!(
	pub enum Runtime where
		Block = Block,
		NodeBlock = opaque::Block,
		UncheckedExtrinsic = UncheckedExtrinsic
	{
		...
		Session: session::{Module, Call, Storage, Event, Config<T>},
		ValidatorSet: validatorset::{Module, Call, Storage, Event<T>, Config<T>},
		Aura: aura::{Module, Config<T>, Inherent(Timestamp)},
		Grandpa: grandpa::{Module, 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.

fn testnet_genesis(initial_authorities: Vec<(AccountId, AuraId, GrandpaId)>,
	root_key: AccountId,
	endowed_accounts: Vec<AccountId>,
	_enable_println: bool) -> GenesisConfig {
	GenesisConfig {
		...,
		validatorset: Some(ValidatorSetConfig {
			validators: initial_authorities.iter().map(|x| x.0.clone()).collect::<Vec<_>>(),
		}),
		session: Some(SessionConfig {
			keys: initial_authorities.iter().map(|x| {
				(x.0.clone(), x.0.clone(), session_keys(x.1.clone(), x.2.clone()))
			}).collect::<Vec<_>>(),
		}),
		aura: Some(AuraConfig {
			authorities: vec![],
		}),
		grandpa: Some(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 src/chain_spec.rs:

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

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

• cargo build --release and then cargo run --release -- --dev

Sample

The usage of this pallet are demonstrated in the Substrate permissioning sample.

Additional 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.

Source Code:
ValidatorSet Pallet: https://github.com/gautamdhameja/substrate-validator-set
Permissioning Sample: https://github.com/gautamdhameja/substrate-permissioning

#substrate #poa #blockchain