paras: `initialize_para_now` and `ParachainsCache` (#4934)

This commit adds a new primitive called `ParachainsCache` to manipulate
the `Parachains` storage entry in a more convenient way.

Then, on top of that, this commit changes the logic of
`initialize_para_now` so that it is identical to what is used for
initialization of onboarding.

polkadot/runtime/parachains/src/hrmp/benchmarking.rs

@@ -17,7 +17,7 @@
 use crate::{
 	configuration::Pallet as Configuration,
 	hrmp::{Pallet as Hrmp, *},
-	paras::Pallet as Paras,
+	paras::{Pallet as Paras, ParachainsCache},
 	shared::Pallet as Shared,
 };
 use frame_support::{assert_ok, traits::Currency};
@@ -26,14 +26,16 @@ type BalanceOf<T> =
 	<<T as Config>::Currency as Currency<<T as frame_system::Config>::AccountId>>::Balance;
 
 fn register_parachain_with_balance<T: Config>(id: ParaId, balance: BalanceOf<T>) {
-	assert_ok!(Paras::<T>::initialize_para_now(
+	let mut parachains = ParachainsCache::new();
+	Paras::<T>::initialize_para_now(
+		&mut parachains,
 		id,
-		crate::paras::ParaGenesisArgs {
+		&crate::paras::ParaGenesisArgs {
 			parachain: true,
 			genesis_head: vec![1].into(),
 			validation_code: vec![1].into(),
 		},
-	));
+	);
 	T::Currency::make_free_balance_be(&id.into_account(), balance);
 }
 

polkadot/runtime/parachains/src/paras/mod.rs

@@ -537,6 +537,8 @@ pub mod pallet {
 		StorageValue<_, Vec<ValidationCodeHash>, ValueQuery>;
 
 	/// All parachains. Ordered ascending by `ParaId`. Parathreads are not included.
+	///
+	/// Consider using the [`ParachainsCache`] type of modifying.
 	#[pallet::storage]
 	#[pallet::getter(fn parachains)]
 	pub(crate) type Parachains<T: Config> = StorageValue<_, Vec<ParaId>, ValueQuery>;
@@ -683,30 +685,14 @@ pub mod pallet {
 	#[pallet::genesis_build]
 	impl<T: Config> GenesisBuild<T> for GenesisConfig {
 		fn build(&self) {
-			let mut parachains: Vec<_> = self
-				.paras
-				.iter()
-				.filter(|(_, args)| args.parachain)
-				.map(|&(ref id, _)| id)
-				.cloned()
-				.collect();
-
-			parachains.sort();
-			parachains.dedup();
-
-			Parachains::<T>::put(&parachains);
-
+			let mut parachains = ParachainsCache::new();
 			for (id, genesis_args) in &self.paras {
-				let code_hash = genesis_args.validation_code.hash();
-				<Pallet<T>>::increase_code_ref(&code_hash, &genesis_args.validation_code);
-				<Pallet<T> as Store>::CurrentCodeHash::insert(&id, &code_hash);
-				<Pallet<T> as Store>::Heads::insert(&id, &genesis_args.genesis_head);
-				if genesis_args.parachain {
-					ParaLifecycles::<T>::insert(&id, ParaLifecycle::Parachain);
-				} else {
-					ParaLifecycles::<T>::insert(&id, ParaLifecycle::Parathread);
+				if genesis_args.validation_code.0.is_empty() {
+					panic!("empty validation code is not allowed in genesis");
 				}
+				Pallet::<T>::initialize_para_now(&mut parachains, *id, genesis_args);
 			}
+			// parachains are flushed on drop
 		}
 	}
 
@@ -1082,7 +1068,7 @@ impl<T: Config> Pallet<T> {
 	// Returns the list of outgoing paras from the actions queue.
 	fn apply_actions_queue(session: SessionIndex) -> Vec<ParaId> {
 		let actions = ActionsQueue::<T>::take(session);
-		let mut parachains = <Self as Store>::Parachains::get();
+		let mut parachains = ParachainsCache::new();
 		let now = <frame_system::Pallet<T>>::block_number();
 		let mut outgoing = Vec::new();
 
@@ -1093,49 +1079,23 @@ impl<T: Config> Pallet<T> {
 				},
 				Some(ParaLifecycle::Onboarding) => {
 					if let Some(genesis_data) = <Self as Store>::UpcomingParasGenesis::take(&para) {
-						if genesis_data.parachain {
-							if let Err(i) = parachains.binary_search(&para) {
-								parachains.insert(i, para);
-							}
-							ParaLifecycles::<T>::insert(&para, ParaLifecycle::Parachain);
-						} else {
-							ParaLifecycles::<T>::insert(&para, ParaLifecycle::Parathread);
-						}
-
-						// HACK: see the notice in `schedule_para_initialize`.
-						//
-						// Apparently, this is left over from a prior version of the runtime.
-						// To handle this we just insert the code and link the current code hash
-						// to it.
-						if !genesis_data.validation_code.0.is_empty() {
-							let code_hash = genesis_data.validation_code.hash();
-							Self::increase_code_ref(&code_hash, &genesis_data.validation_code);
-							<Self as Store>::CurrentCodeHash::insert(&para, code_hash);
-						}
-
-						<Self as Store>::Heads::insert(&para, genesis_data.genesis_head);
+						Self::initialize_para_now(&mut parachains, para, &genesis_data);
 					}
 				},
 				// Upgrade a parathread to a parachain
 				Some(ParaLifecycle::UpgradingParathread) => {
-					if let Err(i) = parachains.binary_search(&para) {
-						parachains.insert(i, para);
-					}
+					parachains.add(para);
 					ParaLifecycles::<T>::insert(&para, ParaLifecycle::Parachain);
 				},
 				// Downgrade a parachain to a parathread
 				Some(ParaLifecycle::DowngradingParachain) => {
-					if let Ok(i) = parachains.binary_search(&para) {
-						parachains.remove(i);
-					}
+					parachains.remove(para);
 					ParaLifecycles::<T>::insert(&para, ParaLifecycle::Parathread);
 				},
 				// Offboard a parathread or parachain from the system
 				Some(ParaLifecycle::OffboardingParachain) |
 				Some(ParaLifecycle::OffboardingParathread) => {
-					if let Ok(i) = parachains.binary_search(&para) {
-						parachains.remove(i);
-					}
+					parachains.remove(para);
 
 					<Self as Store>::Heads::remove(&para);
 					<Self as Store>::FutureCodeUpgrades::remove(&para);
@@ -1178,8 +1138,8 @@ impl<T: Config> Pallet<T> {
 			});
 		}
 
-		// Place the new parachains set in storage.
-		<Self as Store>::Parachains::set(parachains);
+		// Persist parachains into the storage explicitly.
+		drop(parachains);
 
 		return outgoing
 	}
@@ -1994,19 +1954,73 @@ impl<T: Config> Pallet<T> {
 		Heads::<T>::insert(para_id, head_data);
 	}
 
-	#[cfg(feature = "runtime-benchmarks")]
-	pub(crate) fn initialize_para_now(id: ParaId, genesis: ParaGenesisArgs) -> DispatchResult {
-		// first queue this para actions..
-		let _ = Self::schedule_para_initialize(id, genesis)?;
+	/// A low-level function to eagerly initialize a given para.
+	pub(crate) fn initialize_para_now(
+		parachains: &mut ParachainsCache<T>,
+		id: ParaId,
+		genesis_data: &ParaGenesisArgs,
+	) {
+		if genesis_data.parachain {
+			parachains.add(id);
+			ParaLifecycles::<T>::insert(&id, ParaLifecycle::Parachain);
+		} else {
+			ParaLifecycles::<T>::insert(&id, ParaLifecycle::Parathread);
+		}
+
+		// HACK: see the notice in `schedule_para_initialize`.
+		//
+		// Apparently, this is left over from a prior version of the runtime.
+		// To handle this we just insert the code and link the current code hash
+		// to it.
+		if !genesis_data.validation_code.0.is_empty() {
+			let code_hash = genesis_data.validation_code.hash();
+			Self::increase_code_ref(&code_hash, &genesis_data.validation_code);
+			CurrentCodeHash::<T>::insert(&id, code_hash);
+		}
+
+		Heads::<T>::insert(&id, &genesis_data.genesis_head);
+	}
+}
+
+/// An overlay over the `Parachains` storage entry that provides a convenient interface for adding
+/// or removing parachains in bulk.
+pub(crate) struct ParachainsCache<T: Config> {
+	// `None` here means the parachains list has not been accessed yet, nevermind modified.
+	parachains: Option<Vec<ParaId>>,
+	_config: PhantomData<T>,
+}
 
-		// .. and immediately apply them.
-		Self::apply_actions_queue(Self::scheduled_session());
+impl<T: Config> ParachainsCache<T> {
+	pub fn new() -> Self {
+		Self { parachains: None, _config: PhantomData }
+	}
 
-		// ensure it has become a para.
-		ensure!(
-			ParaLifecycles::<T>::get(id) == Some(ParaLifecycle::Parachain),
-			"Parachain not created properly"
-		);
-		Ok(())
+	fn ensure_initialized(&mut self) -> &mut Vec<ParaId> {
+		self.parachains.get_or_insert_with(|| Parachains::<T>::get())
+	}
+
+	/// Adds the given para id to the list.
+	pub fn add(&mut self, id: ParaId) {
+		let parachains = self.ensure_initialized();
+		if let Err(i) = parachains.binary_search(&id) {
+			parachains.insert(i, id);
+		}
+	}
+
+	/// Removes the given para id from the list of parachains. Does nothing if the id is not in the
+	/// list.
+	pub fn remove(&mut self, id: ParaId) {
+		let parachains = self.ensure_initialized();
+		if let Ok(i) = parachains.binary_search(&id) {
+			parachains.remove(i);
+		}
+	}
+}
+
+impl<T: Config> Drop for ParachainsCache<T> {
+	fn drop(&mut self) {
+		if let Some(parachains) = self.parachains.take() {
+			Parachains::<T>::put(&parachains);
+		}
 	}
 }

polkadot/runtime/parachains/src/paras/tests.rs

@@ -1020,6 +1020,7 @@ fn pvf_check_coalescing_onboarding_and_upgrade() {
 
 	let a = ParaId::from(111);
 	let b = ParaId::from(222);
+	let existing_code: ValidationCode = vec![1, 2, 3].into();
 	let validation_code: ValidationCode = vec![3, 2, 1].into();
 
 	let paras = vec![(
@@ -1027,7 +1028,7 @@ fn pvf_check_coalescing_onboarding_and_upgrade() {
 		ParaGenesisArgs {
 			parachain: true,
 			genesis_head: Default::default(),
-			validation_code: ValidationCode(vec![]), // valid since in genesis
+			validation_code: existing_code,
 		},
 	)];
 
@@ -1159,6 +1160,7 @@ fn pvf_check_onboarding_reject_on_expiry() {
 #[test]
 fn pvf_check_upgrade_reject() {
 	let a = ParaId::from(111);
+	let old_code: ValidationCode = vec![1, 2, 3].into();
 	let new_code: ValidationCode = vec![3, 2, 1].into();
 
 	let paras = vec![(
@@ -1166,7 +1168,7 @@ fn pvf_check_upgrade_reject() {
 		ParaGenesisArgs {
 			parachain: false,
 			genesis_head: Default::default(),
-			validation_code: ValidationCode(vec![]), // valid since in genesis
+			validation_code: old_code,
 		},
 	)];