extract ShiftSessionManager into separate pallet (paritytech#342)

jonathanudd · Apr 10, 2024 · 6df0341 · 6df0341
1 parent 8589400
commit 6df0341
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Showing 4 changed files with 289 additions and 92 deletions.
diff --git a/bridges/bin/node/runtime/Cargo.toml b/bridges/bin/node/runtime/Cargo.toml
@@ -78,6 +78,11 @@ tag = 'v2.0.0-rc6'
 default-features = false
 git = "https://github.com/paritytech/substrate/"
 
+[dependencies.pallet-shift-session-manager]
+version = "0.1.0"
+default-features = false
+path = "../../../modules/shift-session-manager"
+
 [dependencies.pallet-sudo]
 version = "2.0.0-rc6"
 tag = 'v2.0.0-rc6'
@@ -264,6 +269,7 @@ std = [
 	"pallet-bridge-eth-poa/std",
 	"pallet-grandpa/std",
 	"pallet-randomness-collective-flip/std",
+	"pallet-shift-session-manager/std",
 	"pallet-sudo/std",
 	"pallet-timestamp/std",
 	"pallet-transaction-payment/std",

diff --git a/bridges/bin/node/runtime/src/lib.rs b/bridges/bin/node/runtime/src/lib.rs
@@ -35,7 +35,6 @@ pub mod benches;
 pub mod kovan;
 pub mod rialto;
 
-use codec::{Decode, Encode};
 use pallet_grandpa::{fg_primitives, AuthorityId as GrandpaId, AuthorityList as GrandpaAuthorityList};
 use sp_api::impl_runtime_apis;
 use sp_consensus_aura::sr25519::AuthorityId as AuraId;
@@ -401,63 +400,14 @@ impl pallet_session::Trait for Runtime {
 	type ValidatorIdOf = ();
 	type ShouldEndSession = pallet_session::PeriodicSessions<Period, Offset>;
 	type NextSessionRotation = pallet_session::PeriodicSessions<Period, Offset>;
-	type SessionManager = ShiftSessionManager;
+	type SessionManager = pallet_shift_session_manager::Module<Runtime>;
 	type SessionHandler = <SessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = SessionKeys;
 	type DisabledValidatorsThreshold = ();
 	type WeightInfo = ();
 }
 
-pub struct ShiftSessionManager;
-
-impl ShiftSessionManager {
-	/// Select validators for session.
-	fn select_validators(
-		session_index: sp_staking::SessionIndex,
-		available_validators: &[AccountId],
-	) -> Vec<AccountId> {
-		let available_validators_count = available_validators.len();
-		let count = sp_std::cmp::max(1, 2 * available_validators_count / 3);
-		let offset = session_index as usize % available_validators_count;
-		let end = offset + count;
-		let session_validators = match end.overflowing_sub(available_validators_count) {
-			(wrapped_end, false) if wrapped_end != 0 => available_validators[offset..]
-				.iter()
-				.chain(available_validators[..wrapped_end].iter())
-				.cloned()
-				.collect(),
-			_ => available_validators[offset..end].to_vec(),
-		};
-
-		session_validators
-	}
-}
-
-impl pallet_session::SessionManager<AccountId> for ShiftSessionManager {
-	fn end_session(_: sp_staking::SessionIndex) {}
-	fn start_session(_: sp_staking::SessionIndex) {}
-	fn new_session(session_index: sp_staking::SessionIndex) -> Option<Vec<AccountId>> {
-		// can't access genesis config here :/
-		if session_index == 0 || session_index == 1 {
-			return None;
-		}
-
-		// the idea that on first call (i.e. when session 1 ends) we're reading current
-		// set of validators from session module (they are initial validators) and save
-		// in our 'local storage'.
-		// then for every session we select (deterministically) 2/3 of these initial
-		// validators to serve validators of new session
-		let available_validators = sp_io::storage::get(b":available_validators")
-			.and_then(|validators| Decode::decode(&mut &validators[..]).ok())
-			.unwrap_or_else(|| {
-				let validators = <pallet_session::Module<Runtime>>::validators();
-				sp_io::storage::set(b":available_validators", &validators.encode());
-				validators
-			});
-
-		Some(Self::select_validators(session_index, &available_validators))
-	}
-}
+impl pallet_shift_session_manager::Trait for Runtime {}
 
 construct_runtime!(
 	pub enum Runtime where
@@ -479,6 +429,7 @@ construct_runtime!(
 		TransactionPayment: pallet_transaction_payment::{Module, Storage},
 		Sudo: pallet_sudo::{Module, Call, Config<T>, Storage, Event<T>},
 		Session: pallet_session::{Module, Call, Storage, Event, Config<T>},
+		ShiftSessionManager: pallet_shift_session_manager::{Module},
 	}
 );
 
@@ -771,46 +722,6 @@ mod tests {
 	use super::*;
 	use bp_currency_exchange::DepositInto;
 
-	#[test]
-	fn shift_session_manager_works() {
-		let acc1 = AccountId::from([1u8; 32]);
-		let acc2 = AccountId::from([2u8; 32]);
-		let acc3 = AccountId::from([3u8; 32]);
-		let acc4 = AccountId::from([4u8; 32]);
-		let acc5 = AccountId::from([5u8; 32]);
-		let all_accs = vec![acc1.clone(), acc2.clone(), acc3.clone(), acc4.clone(), acc5.clone()];
-
-		// at least 1 validator is selected
-		assert_eq!(
-			ShiftSessionManager::select_validators(0, &[acc1.clone()]),
-			vec![acc1.clone()],
-		);
-
-		// at session#0, shift is also 0
-		assert_eq!(
-			ShiftSessionManager::select_validators(0, &all_accs),
-			vec![acc1.clone(), acc2.clone(), acc3.clone()],
-		);
-
-		// at session#1, shift is also 1
-		assert_eq!(
-			ShiftSessionManager::select_validators(1, &all_accs),
-			vec![acc2.clone(), acc3.clone(), acc4.clone()],
-		);
-
-		// at session#3, we're wrapping
-		assert_eq!(
-			ShiftSessionManager::select_validators(3, &all_accs),
-			vec![acc4, acc5, acc1.clone()],
-		);
-
-		// at session#5, we're starting from the beginning again
-		assert_eq!(
-			ShiftSessionManager::select_validators(5, &all_accs),
-			vec![acc1, acc2, acc3],
-		);
-	}
-
 	fn run_deposit_into_test(test: impl Fn(AccountId) -> Balance) {
 		let mut ext: sp_io::TestExternalities = SystemConfig::default().build_storage::<Runtime>().unwrap().into();
 		ext.execute_with(|| {

diff --git a/bridges/modules/shift-session-manager/Cargo.toml b/bridges/modules/shift-session-manager/Cargo.toml
@@ -0,0 +1,67 @@
+[package]
+name = "pallet-shift-session-manager"
+description = "A Substrate Runtime module that selects 2/3 of initial validators for every session"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "1.3.1", default-features = false }
+
+# Substrate Based Dependencies
+
+[dependencies.frame-support]
+version = "2.0.0-rc6"
+tag = 'v2.0.0-rc6'
+default-features = false
+git = "https://github.com/paritytech/substrate/"
+
+[dependencies.frame-system]
+version = "2.0.0-rc6"
+tag = 'v2.0.0-rc6'
+default-features = false
+git = "https://github.com/paritytech/substrate/"
+
+[dependencies.pallet-session]
+version = "2.0.0-rc6"
+tag = 'v2.0.0-rc6'
+default-features = false
+git = "https://github.com/paritytech/substrate/"
+
+[dependencies.sp-core]
+version = "2.0.0-rc6"
+tag = 'v2.0.0-rc6'
+default-features = false
+git = "https://github.com/paritytech/substrate/"
+
+[dependencies.sp-runtime]
+version = "2.0.0-rc6"
+tag = 'v2.0.0-rc6'
+default-features = false
+git = "https://github.com/paritytech/substrate/"
+
+[dependencies.sp-staking]
+version = "2.0.0-rc6"
+tag = 'v2.0.0-rc6'
+default-features = false
+git = "https://github.com/paritytech/substrate/"
+
+[dependencies.sp-std]
+version = "2.0.0-rc6"
+tag = 'v2.0.0-rc6'
+default-features = false
+git = "https://github.com/paritytech/substrate/"
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"frame-support/std",
+	"frame-system/std",
+	"pallet-session/std",
+	"sp-core/std",
+	"sp-runtime/std",
+	"sp-staking/std",
+	"sp-std/std",
+]