feat: collator rotation

Cargo.toml

@@ -6,6 +6,7 @@ members = [
   'math',
   'node',
   'pallets/parameters',
+  'pallets/collator-rotation',
   'runtime/basilisk',
   'pallets/marketplace',
   'pallets/asset-registry',
@@ -58,6 +59,7 @@ pallet-asset-registry = { path = "pallets/asset-registry", default-features = fa
 pallet-ema-oracle = { path = "pallets/ema-oracle", default-features = false}
 pallet-lbp = { path = "pallets/lbp", default-features = false }
 pallet-parameters = { path = "pallets/parameters", default-features = false }
+pallet-collator-rotation = { path = "pallets/collator-rotation", default-features = false }
 pallet-route-executor = { path = "pallets/route-executor", default-features = false }
 pallet-transaction-multi-payment = { path = "pallets/transaction-multi-payment", default-features = false }
 pallet-xyk = { path = "pallets/xyk", default-features = false }

integration-tests/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "runtime-integration-tests"
-version = "1.2.1"
+version = "1.2.2"
 description = "Integration tests"
 authors = ["GalacticCouncil"]
 edition = "2021"

integration-tests/src/sessions.rs

@@ -4,88 +4,54 @@ use basilisk_runtime::CollatorRewards;
 use pallet_session::SessionManager;
 use pretty_assertions::assert_eq;
 use xcm_emulator::TestExt;
+
 #[test]
-fn new_session_should_rotate_collators_list() {
+fn new_session_should_alternate_full_set_and_benched_set() {
 	TestNet::reset();
 
 	Basilisk::execute_with(|| {
-		let collator1 = basilisk::invulnerables()[0].0.clone(); //d435...
-		let collator2 = basilisk::invulnerables()[1].0.clone(); //8eaf...
-		let collator3 = basilisk::invulnerables()[2].0.clone(); //90b5...
-		let collator4 = basilisk::invulnerables()[3].0.clone(); //6ebe...
-		let collator5 = basilisk::invulnerables()[4].0.clone(); //ec5e...
-		let collator6 = basilisk::invulnerables()[5].0.clone(); //9c78...
-		let collator7 = basilisk::invulnerables()[6].0.clone(); //a678...
-		let collator8 = basilisk::invulnerables()[7].0.clone(); //2433...
-		let collator9 = basilisk::invulnerables()[8].0.clone(); //ee28...
-		let collator10 = basilisk::invulnerables()[9].0.clone(); //da53...
+		// Invulnerables are stored sorted by `pallet_collator_selection`, so the
+		// inner `CollatorSelection::new_session` returns them in sorted order.
+		// `pallet_collator_rotation` then benches `(N / 2) % len` on odd sessions
+		// only; even sessions pass the full set through unchanged.
+		let collator1 = basilisk::invulnerables()[0].0.clone(); // d435...
+		let collator2 = basilisk::invulnerables()[1].0.clone(); // 8eaf...
+		let collator3 = basilisk::invulnerables()[2].0.clone(); // 90b5...
+		let collator4 = basilisk::invulnerables()[3].0.clone(); // 6ebe...
+		let collator5 = basilisk::invulnerables()[4].0.clone(); // ec5e...
+		let collator6 = basilisk::invulnerables()[5].0.clone(); // 9c78...
+		let collator7 = basilisk::invulnerables()[6].0.clone(); // a678...
+		let collator8 = basilisk::invulnerables()[7].0.clone(); // 2433...
+		let collator9 = basilisk::invulnerables()[8].0.clone(); // ee28...
+		let collator10 = basilisk::invulnerables()[9].0.clone(); // da53...
+
+		let full_sorted = vec![
+			collator8.clone(),
+			collator4.clone(),
+			collator2.clone(),
+			collator3.clone(),
+			collator6.clone(),
+			collator7.clone(),
+			collator1.clone(),
+			collator10.clone(),
+			collator5.clone(),
+			collator9.clone(),
+		];
 
-		let collators = CollatorRewards::new_session(0).unwrap();
-		assert_eq!(
-			collators,
-			vec![
-				collator8.clone(),
-				collator4.clone(),
-				collator2.clone(),
-				collator3.clone(),
-				collator6.clone(),
-				collator7.clone(),
-				collator1.clone(),
-				collator10.clone(),
-				collator5.clone(),
-				collator9.clone()
-			]
-		);
+		// Session 0 (even): full set, no bench.
+		assert_eq!(CollatorRewards::new_session(0).unwrap(), full_sorted);
 
-		let collators = CollatorRewards::new_session(1).unwrap();
-		assert_eq!(
-			collators,
-			vec![
-				collator4.clone(),
-				collator2.clone(),
-				collator3.clone(),
-				collator6.clone(),
-				collator7.clone(),
-				collator1.clone(),
-				collator10.clone(),
-				collator5.clone(),
-				collator9.clone(),
-				collator8.clone(),
-			]
-		);
+		// Session 1 (odd, bench index 1/2 = 0): collator at sorted position 0.
+		let mut session1 = full_sorted.clone();
+		session1.remove(0);
+		assert_eq!(CollatorRewards::new_session(1).unwrap(), session1);
 
-		let collators = CollatorRewards::new_session(2).unwrap();
-		assert_eq!(
-			collators,
-			vec![
-				collator2.clone(),
-				collator3.clone(),
-				collator6.clone(),
-				collator7.clone(),
-				collator1.clone(),
-				collator10.clone(),
-				collator5.clone(),
-				collator9.clone(),
-				collator8.clone(),
-				collator4.clone(),
-			]
-		);
+		// Session 2 (even): full set returns.
+		assert_eq!(CollatorRewards::new_session(2).unwrap(), full_sorted);
 
-		let collators = CollatorRewards::new_session(3).unwrap();
-		assert_eq!(
-			collators,
-			vec![
-				collator3.clone(),
-				collator6.clone(),
-				collator7.clone(),
-				collator1.clone(),
-				collator10.clone(),
-				collator5.clone(),
-				collator9.clone(),
-				collator8.clone(),
-				collator4.clone(),
-				collator2.clone(),
-			]
-		);
+		// Session 3 (odd, bench index 3/2 = 1): collator at sorted position 1.
+		let mut session3 = full_sorted.clone();
+		session3.remove(1);
+		assert_eq!(CollatorRewards::new_session(3).unwrap(), session3);
 	});
 }

pallets/collator-rotation/Cargo.toml

@@ -0,0 +1,43 @@
+[package]
+name = "pallet-collator-rotation"
+version = "1.0.0"
+authors = ["GalacticCouncil"]
+edition = "2021"
+license = "Apache-2.0"
+homepage = "https://github.com/galacticcouncil/Basilisk-node"
+repository = "https://github.com/galacticcouncil/Basilisk-node"
+description = "Wraps a SessionManager and benches one collator per session, rotating by session index"
+
+[dependencies]
+codec = { workspace = true, features = ["derive", "max-encoded-len"] }
+scale-info = { workspace = true }
+frame-support = { workspace = true }
+frame-system = { workspace = true }
+pallet-session = { workspace = true }
+sp-staking = { workspace = true }
+sp-std = { workspace = true }
+
+[dev-dependencies]
+sp-core = { workspace = true }
+sp-io = { workspace = true }
+sp-runtime = { workspace = true }
+
+[features]
+default = ["std"]
+std = [
+    "codec/std",
+    "scale-info/std",
+    "frame-support/std",
+    "frame-system/std",
+    "pallet-session/std",
+    "sp-staking/std",
+    "sp-std/std",
+    "sp-core/std",
+    "sp-io/std",
+    "sp-runtime/std",
+]
+try-runtime = [
+    "frame-support/try-runtime",
+    "frame-system/try-runtime",
+    "pallet-session/try-runtime",
+]

pallets/collator-rotation/src/lib.rs

@@ -0,0 +1,63 @@
+// This file is part of Basilisk-node.
+//
+// Copyright (C) 2020-2026  Intergalactic, Limited (GIB).
+// SPDX-License-Identifier: Apache-2.0
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[cfg(test)]
+mod mock;
+#[cfg(test)]
+mod tests;
+
+pub use pallet::*;
+
+use pallet_session::SessionManager;
+use sp_staking::SessionIndex;
+use sp_std::vec::Vec;
+
+#[frame_support::pallet]
+pub mod pallet {
+	use super::*;
+
+	#[pallet::config]
+	pub trait Config: frame_system::Config<RuntimeEvent: From<Event<Self>>> {
+		type Inner: SessionManager<Self::AccountId>;
+	}
+
+	#[pallet::pallet]
+	pub struct Pallet<T>(_);
+
+	#[pallet::event]
+	#[pallet::generate_deposit(pub(crate) fn deposit_event)]
+	pub enum Event<T: Config> {
+		CollatorBenched {
+			who: T::AccountId,
+			session_index: SessionIndex,
+		},
+	}
+}
+
+impl<T: Config> SessionManager<T::AccountId> for Pallet<T> {
+	fn new_session(new_index: SessionIndex) -> Option<Vec<T::AccountId>> {
+		let mut collators = T::Inner::new_session(new_index)?;
+		// bench 1 collator every odd session rotation
+		if new_index % 2 == 1 && collators.len() > 1 {
+			let bench_idx = ((new_index / 2) as usize) % collators.len();
+			let benched = collators.remove(bench_idx);
+			Self::deposit_event(Event::CollatorBenched {
+				who: benched,
+				session_index: new_index,
+			});
+		}
+		Some(collators)
+	}
+
+	fn end_session(end_index: SessionIndex) {
+		T::Inner::end_session(end_index)
+	}
+
+	fn start_session(start_index: SessionIndex) {
+		T::Inner::start_session(start_index)
+	}
+}