Replace free for all collation in cumulus runtimes (#1251)

Partially fixes #103 

This PR removes instances of "free for all" collation in the `glutton`,
`shell`, and `seedling` runtimes and replaces them with Aura instances.
Aura is configured without a session manager, so the initial authority
set cannot be changed later on.

---------

Signed-off-by: georgepisaltu <george.pisaltu@parity.io>

cumulus/parachains/runtimes/starters/shell/src/lib.rs

@@ -32,13 +32,14 @@ include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 pub mod xcm_config;
 
 use codec::{Decode, Encode};
-use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
+use cumulus_pallet_parachain_system::RelayNumberMonotonicallyIncreases;
 use frame_support::unsigned::TransactionValidityError;
 use scale_info::TypeInfo;
 use sp_api::impl_runtime_apis;
-use sp_core::OpaqueMetadata;
+pub use sp_consensus_aura::sr25519::AuthorityId as AuraId;
+use sp_core::{crypto::KeyTypeId, OpaqueMetadata};
 use sp_runtime::{
-	create_runtime_str, generic,
+	create_runtime_str, generic, impl_opaque_keys,
 	traits::{AccountIdLookup, BlakeTwo256, Block as BlockT, DispatchInfoOf},
 	transaction_validity::{TransactionSource, TransactionValidity},
 	ApplyExtrinsicResult,
@@ -53,7 +54,7 @@ pub use frame_support::{
 	construct_runtime,
 	dispatch::DispatchClass,
 	parameter_types,
-	traits::{Everything, IsInVec, Randomness},
+	traits::{ConstBool, ConstU32, ConstU64, ConstU8, EitherOfDiverse, IsInVec, Randomness},
 	weights::{
 		constants::{
 			BlockExecutionWeight, ExtrinsicBaseWeight, RocksDbWeight, WEIGHT_REF_TIME_PER_SECOND,
@@ -68,6 +69,12 @@ use parachains_common::{AccountId, Signature};
 pub use sp_runtime::BuildStorage;
 pub use sp_runtime::{Perbill, Permill};
 
+impl_opaque_keys! {
+	pub struct SessionKeys {
+		pub aura: Aura,
+	}
+}
+
 /// This runtime version.
 #[sp_version::runtime_version]
 pub const VERSION: RuntimeVersion = RuntimeVersion {
@@ -87,6 +94,15 @@ pub fn native_version() -> NativeVersion {
 	NativeVersion { runtime_version: VERSION, can_author_with: Default::default() }
 }
 
+/// Maximum number of blocks simultaneously accepted by the Runtime, not yet included
+/// into the relay chain.
+const UNINCLUDED_SEGMENT_CAPACITY: u32 = 1;
+/// How many parachain blocks are processed by the relay chain per parent. Limits the
+/// number of blocks authored per slot.
+const BLOCK_PROCESSING_VELOCITY: u32 = 1;
+/// Relay chain slot duration, in milliseconds.
+const RELAY_CHAIN_SLOT_DURATION_MILLIS: u32 = 6000;
+
 /// We assume that ~10% of the block weight is consumed by `on_initialize` handlers.
 /// This is used to limit the maximal weight of a single extrinsic.
 const AVERAGE_ON_INITIALIZE_RATIO: Perbill = Perbill::from_percent(10);
@@ -177,16 +193,41 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type ReservedDmpWeight = ReservedDmpWeight;
 	type XcmpMessageHandler = ();
 	type ReservedXcmpWeight = ();
-	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
-	type ConsensusHook = cumulus_pallet_parachain_system::consensus_hook::ExpectParentIncluded;
+	type CheckAssociatedRelayNumber = RelayNumberMonotonicallyIncreases;
+	type ConsensusHook = cumulus_pallet_aura_ext::FixedVelocityConsensusHook<
+		Runtime,
+		RELAY_CHAIN_SLOT_DURATION_MILLIS,
+		BLOCK_PROCESSING_VELOCITY,
+		UNINCLUDED_SEGMENT_CAPACITY,
+	>;
 }
 
 impl parachain_info::Config for Runtime {}
 
+impl cumulus_pallet_aura_ext::Config for Runtime {}
+
+impl pallet_aura::Config for Runtime {
+	type AuthorityId = AuraId;
+	type DisabledValidators = ();
+	type MaxAuthorities = ConstU32<100_000>;
+	type AllowMultipleBlocksPerSlot = ConstBool<false>;
+	#[cfg(feature = "experimental")]
+	type SlotDuration = pallet_aura::MinimumPeriodTimesTwo<Self>;
+}
+
+impl pallet_timestamp::Config for Runtime {
+	type Moment = u64;
+	type OnTimestampSet = Aura;
+	type MinimumPeriod = ConstU64<0>;
+	type WeightInfo = ();
+}
+
 construct_runtime! {
 	pub enum Runtime
 	{
 		System: frame_system::{Pallet, Call, Storage, Config<T>, Event<T>},
+		Timestamp: pallet_timestamp::{Pallet, Call, Storage, Inherent},
+
 		ParachainSystem: cumulus_pallet_parachain_system::{
 			Pallet, Call, Config<T>, Storage, Inherent, Event<T>, ValidateUnsigned,
 		},
@@ -194,6 +235,9 @@ construct_runtime! {
 
 		// DMP handler.
 		CumulusXcm: cumulus_pallet_xcm::{Pallet, Call, Storage, Event<T>, Origin},
+
+		Aura: pallet_aura::{Pallet, Storage, Config<T>},
+		AuraExt: cumulus_pallet_aura_ext::{Pallet, Storage, Config<T>},
 	}
 }
 
@@ -263,6 +307,16 @@ pub type Executive = frame_executive::Executive<
 >;
 
 impl_runtime_apis! {
+	impl sp_consensus_aura::AuraApi<Block, AuraId> for Runtime {
+		fn slot_duration() -> sp_consensus_aura::SlotDuration {
+			sp_consensus_aura::SlotDuration::from_millis(Aura::slot_duration())
+		}
+
+		fn authorities() -> Vec<AuraId> {
+			Aura::authorities().into_inner()
+		}
+	}
+
 	impl sp_api::Core<Block> for Runtime {
 		fn version() -> RuntimeVersion {
 			VERSION
@@ -328,12 +382,14 @@ impl_runtime_apis! {
 	}
 
 	impl sp_session::SessionKeys<Block> for Runtime {
-		fn decode_session_keys(_: Vec<u8>) -> Option<Vec<(Vec<u8>, sp_core::crypto::KeyTypeId)>> {
-			Some(Vec::new())
+		fn generate_session_keys(seed: Option<Vec<u8>>) -> Vec<u8> {
+			SessionKeys::generate(seed)
 		}
 
-		fn generate_session_keys(_: Option<Vec<u8>>) -> Vec<u8> {
-			Vec::new()
+		fn decode_session_keys(
+			encoded: Vec<u8>,
+		) -> Option<Vec<(Vec<u8>, KeyTypeId)>> {
+			SessionKeys::decode_into_raw_public_keys(&encoded)
 		}
 	}
 
@@ -346,5 +402,5 @@ impl_runtime_apis! {
 
 cumulus_pallet_parachain_system::register_validate_block! {
 	Runtime = Runtime,
-	BlockExecutor = Executive,
+	BlockExecutor = cumulus_pallet_aura_ext::BlockExecutor::<Runtime, Executive>,
 }