registrar.rs

// Copyright 2017-2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.

// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.

//! Module to handle which parachains/parathreads (collectively referred to as "paras") are
//! registered and which are scheduled. Doesn't manage any of the actual execution/validation logic
//! which is left to `parachains.rs`.

use sp_std::{prelude::*, result};
#[cfg(any(feature = "std", test))]
use sp_std::marker::PhantomData;
use codec::{Encode, Decode};

use sp_runtime::{
	transaction_validity::{TransactionValidityError, ValidTransaction, TransactionValidity},
	traits::{Hash as HashT, SignedExtension}
};

use frame_support::{
	decl_storage, decl_module, decl_event, decl_error, ensure,
	dispatch::{DispatchResult, IsSubType}, traits::{Get, Currency, ReservableCurrency},
	weights::{SimpleDispatchInfo, DispatchInfo},
};
use system::{self, ensure_root, ensure_signed};
use primitives::parachain::{
	Id as ParaId, CollatorId, Scheduling, LOWEST_USER_ID, SwapAux, Info as ParaInfo, ActiveParas,
	Retriable
};
use crate::parachains;
use sp_runtime::transaction_validity::InvalidTransaction;

/// Parachain registration API.
pub trait Registrar<AccountId> {
	/// Create a new unique parachain identity for later registration.
	fn new_id() -> ParaId;

	/// Checks whether the given initial head data size falls within the limit.
	fn head_data_size_allowed(head_data_size: u32) -> bool;

	/// Checks whether the given validation code falls within the limit.
	fn code_size_allowed(code_size: u32) -> bool;

	/// Register a parachain with given `code` and `initial_head_data`. `id` must not yet be registered or it will
	/// result in a error.
	///
	/// This does not enforce any code size or initial head data limits, as these
	/// are governable and parameters for parachain initialization are often
	/// determined long ahead-of-time. Not checking these values ensures that changes to limits
	/// do not invalidate in-progress auction winners.
	fn register_para(
		id: ParaId,
		info: ParaInfo,
		code: Vec<u8>,
		initial_head_data: Vec<u8>,
	) -> DispatchResult;

	/// Deregister a parachain with given `id`. If `id` is not currently registered, an error is returned.
	fn deregister_para(id: ParaId) -> DispatchResult;
}

impl<T: Trait> Registrar<T::AccountId> for Module<T> {
	fn new_id() -> ParaId {
		<NextFreeId>::mutate(|n| { let r = *n; *n = ParaId::from(u32::from(*n) + 1); r })
	}

	fn head_data_size_allowed(head_data_size: u32) -> bool {
		head_data_size <= <T as parachains::Trait>::MaxHeadDataSize::get()
	}

	fn code_size_allowed(code_size: u32) -> bool {
		code_size <= <T as parachains::Trait>::MaxCodeSize::get()
	}

	fn register_para(
		id: ParaId,
		info: ParaInfo,
		code: Vec<u8>,
		initial_head_data: Vec<u8>,
	) -> DispatchResult {
		ensure!(!Paras::contains_key(id), Error::<T>::ParaAlreadyExists);
		if let Scheduling::Always = info.scheduling {
			Parachains::mutate(|parachains|
				match parachains.binary_search(&id) {
					Ok(_) => Err(Error::<T>::ParaAlreadyExists),
					Err(idx) => {
						parachains.insert(idx, id);
						Ok(())
					}
				}
			)?;
		}
		<parachains::Module<T>>::initialize_para(id, code, initial_head_data);
		Paras::insert(id, info);
		Ok(())
	}

	fn deregister_para(id: ParaId) -> DispatchResult {
		let info = Paras::take(id).ok_or(Error::<T>::InvalidChainId)?;
		if let Scheduling::Always = info.scheduling {
			Parachains::mutate(|parachains|
				parachains.binary_search(&id)
					.map(|index| parachains.remove(index))
					.map_err(|_| Error::<T>::InvalidChainId)
			)?;
		}
		<parachains::Module<T>>::cleanup_para(id);
		Paras::remove(id);
		Ok(())
	}
}

type BalanceOf<T> =
	<<T as Trait>::Currency as Currency<<T as system::Trait>::AccountId>>::Balance;

pub trait Trait: parachains::Trait {
	/// The overarching event type.
	type Event: From<Event> + Into<<Self as system::Trait>::Event>;

	/// The aggregated origin type must support the parachains origin. We require that we can
	/// infallibly convert between this origin and the system origin, but in reality, they're the
	/// same type, we just can't express that to the Rust type system without writing a `where`
	/// clause everywhere.
	type Origin: From<<Self as system::Trait>::Origin>
		+ Into<result::Result<parachains::Origin, <Self as Trait>::Origin>>;

	/// The system's currency for parathread payment.
	type Currency: ReservableCurrency<Self::AccountId>;

	/// The deposit to be paid to run a parathread.
	type ParathreadDeposit: Get<BalanceOf<Self>>;

	/// Handler for when two ParaIds are swapped.
	type SwapAux: SwapAux;

	/// The number of items in the parathread queue, aka the number of blocks in advance to schedule
	/// parachain execution.
	type QueueSize: Get<usize>;

	/// The number of rotations that you will have as grace if you miss a block.
	type MaxRetries: Get<u32>;
}

decl_storage! {
	trait Store for Module<T: Trait> as Registrar {
		// Vector of all parachain IDs, in ascending order.
		Parachains: Vec<ParaId>;

		/// The number of threads to schedule per block.
		ThreadCount: u32;

		/// An array of the queue of set of threads scheduled for the coming blocks; ordered by
		/// ascending para ID. There can be no duplicates of para ID in each list item.
		SelectedThreads: Vec<Vec<(ParaId, CollatorId)>>;

		/// Parathreads/chains scheduled for execution this block. If the collator ID is set, then
		/// a particular collator has already been chosen for the next block, and no other collator
		/// may provide the block. In this case we allow the possibility of the combination being
		/// retried in a later block, expressed by `Retriable`.
		///
		/// Ordered by ParaId.
		Active: Vec<(ParaId, Option<(CollatorId, Retriable)>)>;

		/// The next unused ParaId value. Start this high in order to keep low numbers for
		/// system-level chains.
		NextFreeId: ParaId = LOWEST_USER_ID;

		/// Pending swap operations.
		PendingSwap: map hasher(twox_64_concat) ParaId => Option<ParaId>;

		/// Map of all registered parathreads/chains.
		Paras get(fn paras): map hasher(twox_64_concat) ParaId => Option<ParaInfo>;

		/// The current queue for parathreads that should be retried.
		RetryQueue get(fn retry_queue): Vec<Vec<(ParaId, CollatorId)>>;

		/// Users who have paid a parathread's deposit
		Debtors: map hasher(twox_64_concat) ParaId => T::AccountId;
	}
	add_extra_genesis {
		config(parachains): Vec<(ParaId, Vec<u8>, Vec<u8>)>;
		config(_phdata): PhantomData<T>;
		build(build::<T>);
	}
}

#[cfg(feature = "std")]
fn build<T: Trait>(config: &GenesisConfig<T>) {
	let mut p = config.parachains.clone();