initializer for addition genesis config

runtime/parachains/src/initializer.rs

@@ -19,15 +19,14 @@
 //!
 //! This module can throw fatal errors if session-change notifications are received after initialization.
 
-use sp_std::prelude::*;
-use frame_support::weights::Weight;
-use primitives::{
-	parachain::{ValidatorId},
-};
-use frame_support::{
-	decl_storage, decl_module, decl_error, traits::Randomness,
+use crate::{
+	configuration::{self, HostConfiguration},
+	paras, scheduler,
 };
-use crate::{configuration::{self, HostConfiguration}, paras, scheduler};
+use frame_support::weights::Weight;
+use frame_support::{decl_error, decl_module, decl_storage, traits::Randomness};
+use primitives::parachain::ValidatorId;
+use sp_std::prelude::*;
 
 /// Information about a session change that has just occurred.
 #[derive(Default, Clone)]
@@ -105,7 +104,8 @@ impl<T: Trait> Module<T> {
 	///
 	/// Panics if the modules have already been initialized.
 	fn on_new_session<'a, I: 'a>(_changed: bool, validators: I, queued: I)
-		where I: Iterator<Item=(&'a T::AccountId, ValidatorId)>
+	where
+		I: Iterator<Item = (&'a T::AccountId, ValidatorId)>,
 	{
 		assert!(HasInitialized::get().is_none());
 
@@ -148,19 +148,29 @@ impl<T: Trait> sp_runtime::BoundToRuntimeAppPublic for Module<T> {
 impl<T: Trait> session::OneSessionHandler<T::AccountId> for Module<T> {
 	type Key = ValidatorId;
 
-	fn on_genesis_session<'a, I: 'a>(_validators: I)
-		where I: Iterator<Item=(&'a T::AccountId, Self::Key)>
+	fn on_genesis_session<'a, I: 'a>(validators: I)
+	where
+		I: Iterator<Item = (&'a T::AccountId, Self::Key)>,
 	{
+		// host config as provided by the client using `fn build` based on the `GenesisConfig`
+
+		// `ValdiatorGroups` are created in `ParasScheduler::initializer_on_new_session(..)`
+		// `Paras` are rotated based on the block number in `Paras::initializer_on_new_session`(..)
+		// `Parathreads` are also removed in `Paras::initializer_on_new_session`
 
+		// a new session is started with session index 0 is started after the fn returns
+		// that code is part of the `add_extra_genesis` block in the `Session` pallet
+		// from there on all code fans out from `Self::on_new_session(..)`
 	}
 
 	fn on_new_session<'a, I: 'a>(changed: bool, validators: I, queued: I)
-		where I: Iterator<Item=(&'a T::AccountId, Self::Key)>
+	where
+		I: Iterator<Item = (&'a T::AccountId, Self::Key)>,
 	{
 		<Module<T>>::on_new_session(changed, validators, queued);
 	}
 
-	fn on_disabled(_i: usize) { }
+	fn on_disabled(_i: usize) {}
 }
 
 #[cfg(test)]