pallet_bridge_messages/

weights_ext.rs

// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Parity Bridges Common.

// Parity Bridges Common 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.

// Parity Bridges Common 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 Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.

//! Weight-related utilities.

use crate::weights::WeightInfo;

use bp_messages::{MessageNonce, UnrewardedRelayersState};
use bp_runtime::{PreComputedSize, Size};
use frame_support::weights::Weight;

/// Size of the message being delivered in benchmarks.
pub const EXPECTED_DEFAULT_MESSAGE_LENGTH: u32 = 128;

/// We assume that size of signed extensions on all our chains and size of all 'small' arguments of
/// calls we're checking here would fit 1KB.
const SIGNED_EXTENSIONS_SIZE: u32 = 1024;

/// Number of extra bytes (excluding size of storage value itself) of storage proof.
/// This mostly depends on number of entries (and their density) in the storage trie.
/// Some reserve is reserved to account future chain growth.
pub const EXTRA_STORAGE_PROOF_SIZE: u32 = 1024;

/// Ensure that weights from `WeightInfoExt` implementation are looking correct.
pub fn ensure_weights_are_correct<W: WeightInfoExt>() {
	// all components of weight formulae must have zero `proof_size`, because the `proof_size` is
	// benchmarked using `MaxEncodedLen` approach and there are no components that cause additional
	// db reads

	// W::receive_messages_proof_outbound_lane_state_overhead().ref_time() may be zero because:
	// the outbound lane state processing code (`InboundLane::receive_state_update`) is minimal and
	// may not be accounted by our benchmarks
	assert_eq!(W::receive_messages_proof_outbound_lane_state_overhead().proof_size(), 0);
	assert_ne!(W::storage_proof_size_overhead(1).ref_time(), 0);
	assert_eq!(W::storage_proof_size_overhead(1).proof_size(), 0);

	// verify `receive_messages_delivery_proof` weight components
	assert_ne!(W::receive_messages_delivery_proof_overhead().ref_time(), 0);
	assert_ne!(W::receive_messages_delivery_proof_overhead().proof_size(), 0);
	// W::receive_messages_delivery_proof_messages_overhead(1).ref_time() may be zero because:
	// there's no code that iterates over confirmed messages in confirmation transaction
	assert_eq!(W::receive_messages_delivery_proof_messages_overhead(1).proof_size(), 0);
	// W::receive_messages_delivery_proof_relayers_overhead(1).ref_time() may be zero because:
	// runtime **can** choose not to pay any rewards to relayers
	// W::receive_messages_delivery_proof_relayers_overhead(1).proof_size() is an exception
	// it may or may not cause additional db reads, so proof size may vary
	assert_ne!(W::storage_proof_size_overhead(1).ref_time(), 0);
	assert_eq!(W::storage_proof_size_overhead(1).proof_size(), 0);

	// verify `receive_message_proof` weight
	let receive_messages_proof_weight =
		W::receive_messages_proof_weight(&PreComputedSize(1), 10, Weight::zero());
	assert_ne!(receive_messages_proof_weight.ref_time(), 0);
	assert_ne!(receive_messages_proof_weight.proof_size(), 0);
	messages_proof_size_does_not_affect_proof_size::<W>();
	messages_count_does_not_affect_proof_size::<W>();

	// verify `receive_message_proof` weight
	let receive_messages_delivery_proof_weight = W::receive_messages_delivery_proof_weight(
		&PreComputedSize(1),
		&UnrewardedRelayersState::default(),
	);
	assert_ne!(receive_messages_delivery_proof_weight.ref_time(), 0);
	assert_ne!(receive_messages_delivery_proof_weight.proof_size(), 0);
	messages_delivery_proof_size_does_not_affect_proof_size::<W>();
	total_messages_in_delivery_proof_does_not_affect_proof_size::<W>();
}

/// Ensure that we are able to dispatch maximal size messages.
pub fn ensure_maximal_message_dispatch<W: WeightInfoExt>(
	max_incoming_message_size: u32,
	max_incoming_message_dispatch_weight: Weight,
) {
	let message_dispatch_weight = W::message_dispatch_weight(max_incoming_message_size);
	assert!(
		message_dispatch_weight.all_lte(max_incoming_message_dispatch_weight),
		"Dispatch weight of maximal message {message_dispatch_weight:?} must be lower \
		than the hardcoded {max_incoming_message_dispatch_weight:?}",
	);
}

/// Ensure that we're able to receive maximal (by-size and by-weight) message from other chain.
pub fn ensure_able_to_receive_message<W: WeightInfoExt>(
	max_extrinsic_size: u32,
	max_extrinsic_weight: Weight,
	max_incoming_message_proof_size: u32,
	max_incoming_message_dispatch_weight: Weight,
) {
	// verify that we're able to receive proof of maximal-size message
	let max_delivery_transaction_size =
		max_incoming_message_proof_size.saturating_add(SIGNED_EXTENSIONS_SIZE);
	assert!(
		max_delivery_transaction_size <= max_extrinsic_size,
		"Size of maximal message delivery transaction {max_incoming_message_proof_size} + \
		{SIGNED_EXTENSIONS_SIZE} is larger than maximal possible transaction size {max_extrinsic_size}",
	);

	// verify that we're able to receive proof of maximal-size message with maximal dispatch weight
	let max_delivery_transaction_dispatch_weight = W::receive_messages_proof_weight(
		&PreComputedSize(
			(max_incoming_message_proof_size + W::expected_extra_storage_proof_size()) as usize,
		),
		1,
		max_incoming_message_dispatch_weight,
	);
	assert!(
		max_delivery_transaction_dispatch_weight.all_lte(max_extrinsic_weight),
		"Weight of maximal message delivery transaction + {max_delivery_transaction_dispatch_weight} is larger than maximal possible transaction weight {max_extrinsic_weight}",
	);
}

/// Ensure that we're able to receive maximal confirmation from other chain.
pub fn ensure_able_to_receive_confirmation<W: WeightInfoExt>(
	max_extrinsic_size: u32,
	max_extrinsic_weight: Weight,
	max_inbound_lane_data_proof_size_from_peer_chain: u32,
	max_unrewarded_relayer_entries_at_peer_inbound_lane: MessageNonce,
	max_unconfirmed_messages_at_inbound_lane: MessageNonce,
) {
	// verify that we're able to receive confirmation of maximal-size
	let max_confirmation_transaction_size =
		max_inbound_lane_data_proof_size_from_peer_chain.saturating_add(SIGNED_EXTENSIONS_SIZE);
	assert!(
		max_confirmation_transaction_size <= max_extrinsic_size,
		"Size of maximal message delivery confirmation transaction {max_inbound_lane_data_proof_size_from_peer_chain} + {SIGNED_EXTENSIONS_SIZE} is larger than maximal possible transaction size {max_extrinsic_size}",
	);

	// verify that we're able to reward maximal number of relayers that have delivered maximal
	// number of messages
	let max_confirmation_transaction_dispatch_weight = W::receive_messages_delivery_proof_weight(
		&PreComputedSize(max_inbound_lane_data_proof_size_from_peer_chain as usize),
		&UnrewardedRelayersState {
			unrewarded_relayer_entries: max_unrewarded_relayer_entries_at_peer_inbound_lane,
			total_messages: max_unconfirmed_messages_at_inbound_lane,
			..Default::default()
		},
	);
	assert!(
		max_confirmation_transaction_dispatch_weight.all_lte(max_extrinsic_weight),
		"Weight of maximal confirmation transaction {max_confirmation_transaction_dispatch_weight} is larger than maximal possible transaction weight {max_extrinsic_weight}",
	);
}

/// Panics if `proof_size` of message delivery call depends on the message proof size.
fn messages_proof_size_does_not_affect_proof_size<W: WeightInfoExt>() {
	let dispatch_weight = Weight::zero();
	let weight_when_proof_size_is_8k =
		W::receive_messages_proof_weight(&PreComputedSize(8 * 1024), 1, dispatch_weight);
	let weight_when_proof_size_is_16k =
		W::receive_messages_proof_weight(&PreComputedSize(16 * 1024), 1, dispatch_weight);

	ensure_weight_components_are_not_zero(weight_when_proof_size_is_8k);
	ensure_weight_components_are_not_zero(weight_when_proof_size_is_16k);
	ensure_proof_size_is_the_same(
		weight_when_proof_size_is_8k,
		weight_when_proof_size_is_16k,
		"Messages proof size does not affect values that we read from our storage",
	);
}

/// Panics if `proof_size` of message delivery call depends on the messages count.
///
/// In practice, it will depend on the messages count, because most probably every
/// message will read something from db during dispatch. But this must be accounted
/// by the `dispatch_weight`.
fn messages_count_does_not_affect_proof_size<W: WeightInfoExt>() {
	let messages_proof_size = PreComputedSize(8 * 1024);
	let dispatch_weight = Weight::zero();
	let weight_of_one_incoming_message =
		W::receive_messages_proof_weight(&messages_proof_size, 1, dispatch_weight);
	let weight_of_two_incoming_messages =
		W::receive_messages_proof_weight(&messages_proof_size, 2, dispatch_weight);

	ensure_weight_components_are_not_zero(weight_of_one_incoming_message);
	ensure_weight_components_are_not_zero(weight_of_two_incoming_messages);
	ensure_proof_size_is_the_same(
		weight_of_one_incoming_message,
		weight_of_two_incoming_messages,
		"Number of same-lane incoming messages does not affect values that we read from our storage",
	);
}

/// Panics if `proof_size` of delivery confirmation call depends on the delivery proof size.
fn messages_delivery_proof_size_does_not_affect_proof_size<W: WeightInfoExt>() {
	let relayers_state = UnrewardedRelayersState {
		unrewarded_relayer_entries: 1,
		messages_in_oldest_entry: 1,
		total_messages: 1,
		last_delivered_nonce: 1,
	};
	let weight_when_proof_size_is_8k =
		W::receive_messages_delivery_proof_weight(&PreComputedSize(8 * 1024), &relayers_state);
	let weight_when_proof_size_is_16k =
		W::receive_messages_delivery_proof_weight(&PreComputedSize(16 * 1024), &relayers_state);

	ensure_weight_components_are_not_zero(weight_when_proof_size_is_8k);
	ensure_weight_components_are_not_zero(weight_when_proof_size_is_16k);
	ensure_proof_size_is_the_same(
		weight_when_proof_size_is_8k,
		weight_when_proof_size_is_16k,
		"Messages delivery proof size does not affect values that we read from our storage",
	);
}

/// Panics if `proof_size` of delivery confirmation call depends on the number of confirmed
/// messages.
fn total_messages_in_delivery_proof_does_not_affect_proof_size<W: WeightInfoExt>() {
	let proof_size = PreComputedSize(8 * 1024);
	let weight_when_1k_messages_confirmed = W::receive_messages_delivery_proof_weight(
		&proof_size,
		&UnrewardedRelayersState {
			unrewarded_relayer_entries: 1,
			messages_in_oldest_entry: 1,
			total_messages: 1024,
			last_delivered_nonce: 1,
		},
	);
	let weight_when_2k_messages_confirmed = W::receive_messages_delivery_proof_weight(
		&proof_size,
		&UnrewardedRelayersState {
			unrewarded_relayer_entries: 1,
			messages_in_oldest_entry: 1,
			total_messages: 2048,
			last_delivered_nonce: 1,
		},
	);

	ensure_weight_components_are_not_zero(weight_when_1k_messages_confirmed);
	ensure_weight_components_are_not_zero(weight_when_2k_messages_confirmed);
	ensure_proof_size_is_the_same(
		weight_when_1k_messages_confirmed,
		weight_when_2k_messages_confirmed,
		"More messages in delivery proof does not affect values that we read from our storage",
	);
}

/// Panics if either Weight' `proof_size` or `ref_time` are zero.
fn ensure_weight_components_are_not_zero(weight: Weight) {
	assert_ne!(weight.ref_time(), 0);
	assert_ne!(weight.proof_size(), 0);
}

/// Panics if `proof_size` of `weight1` is not equal to `proof_size` of `weight2`.
fn ensure_proof_size_is_the_same(weight1: Weight, weight2: Weight, msg: &str) {
	assert_eq!(
		weight1.proof_size(),
		weight2.proof_size(),
		"{msg}: {} must be equal to {}",
		weight1.proof_size(),
		weight2.proof_size(),
	);
}

/// Extended weight info.
pub trait WeightInfoExt: WeightInfo {
	/// Size of proof that is already included in the single message delivery weight.
	///
	/// The message submitter (at source chain) has already covered this cost. But there are two
	/// factors that may increase proof size: (1) the message size may be larger than predefined
	/// and (2) relayer may add extra trie nodes to the proof. So if proof size is larger than
	/// this value, we're going to charge relayer for that.
	fn expected_extra_storage_proof_size() -> u32;

	// Our configuration assumes that the runtime has special signed extensions used to:
	//
	// 1) reject obsolete delivery and confirmation transactions;
	//
	// 2) refund transaction cost to relayer and register his rewards.
	//
	// The checks in (1) are trivial, so its computation weight may be ignored. And we only touch
	// storage values that are read during the call. So we may ignore the weight of this check.
	//
	// However, during (2) we read and update storage values of other pallets
	// (`pallet-bridge-relayers` and balances/assets pallet). So we need to add this weight to the
	// weight of our call. Hence two following methods.

	/// Extra weight that is added to the `receive_messages_proof` call weight by signed extensions
	/// that are declared at runtime level.
	fn receive_messages_proof_overhead_from_runtime() -> Weight;

	/// Extra weight that is added to the `receive_messages_delivery_proof` call weight by signed
	/// extensions that are declared at runtime level.
	fn receive_messages_delivery_proof_overhead_from_runtime() -> Weight;

	// Functions that are directly mapped to extrinsics weights.

	/// Weight of message delivery extrinsic.
	fn receive_messages_proof_weight(
		proof: &impl Size,
		messages_count: u32,
		dispatch_weight: Weight,
	) -> Weight {
		// basic components of extrinsic weight
		let base_weight = Self::receive_n_messages_proof(messages_count);
		let transaction_overhead_from_runtime =
			Self::receive_messages_proof_overhead_from_runtime();
		let outbound_state_delivery_weight =
			Self::receive_messages_proof_outbound_lane_state_overhead();
		let messages_dispatch_weight = dispatch_weight;

		// proof size overhead weight
		let expected_proof_size = EXPECTED_DEFAULT_MESSAGE_LENGTH
			.saturating_mul(messages_count.saturating_sub(1))
			.saturating_add(Self::expected_extra_storage_proof_size());
		let actual_proof_size = proof.size();
		let proof_size_overhead = Self::storage_proof_size_overhead(
			actual_proof_size.saturating_sub(expected_proof_size),
		);

		base_weight
			.saturating_add(transaction_overhead_from_runtime)
			.saturating_add(outbound_state_delivery_weight)
			.saturating_add(messages_dispatch_weight)
			.saturating_add(proof_size_overhead)
	}

	/// Weight of confirmation delivery extrinsic.
	fn receive_messages_delivery_proof_weight(
		proof: &impl Size,
		relayers_state: &UnrewardedRelayersState,
	) -> Weight {
		// basic components of extrinsic weight
		let transaction_overhead = Self::receive_messages_delivery_proof_overhead();
		let transaction_overhead_from_runtime =
			Self::receive_messages_delivery_proof_overhead_from_runtime();
		let messages_overhead =
			Self::receive_messages_delivery_proof_messages_overhead(relayers_state.total_messages);
		let relayers_overhead = Self::receive_messages_delivery_proof_relayers_overhead(
			relayers_state.unrewarded_relayer_entries,
		);

		// proof size overhead weight
		let expected_proof_size = Self::expected_extra_storage_proof_size();
		let actual_proof_size = proof.size();
		let proof_size_overhead = Self::storage_proof_size_overhead(
			actual_proof_size.saturating_sub(expected_proof_size),
		);

		transaction_overhead
			.saturating_add(transaction_overhead_from_runtime)
			.saturating_add(messages_overhead)
			.saturating_add(relayers_overhead)
			.saturating_add(proof_size_overhead)
	}

	// Functions that are used by extrinsics weights formulas.

	/// Returns weight that needs to be accounted when message delivery transaction
	/// (`receive_messages_proof`) is carrying outbound lane state proof.
	fn receive_messages_proof_outbound_lane_state_overhead() -> Weight {
		let weight_of_single_message_and_lane_state =
			Self::receive_single_message_proof_with_outbound_lane_state();
		let weight_of_single_message = Self::receive_single_message_proof();
		weight_of_single_message_and_lane_state.saturating_sub(weight_of_single_message)
	}

	/// Returns weight overhead of delivery confirmation transaction
	/// (`receive_messages_delivery_proof`).
	fn receive_messages_delivery_proof_overhead() -> Weight {
		let weight_of_two_messages_and_two_tx_overheads =
			Self::receive_delivery_proof_for_single_message().saturating_mul(2);
		let weight_of_two_messages_and_single_tx_overhead =
			Self::receive_delivery_proof_for_two_messages_by_single_relayer();
		weight_of_two_messages_and_two_tx_overheads
			.saturating_sub(weight_of_two_messages_and_single_tx_overhead)
	}

	/// Returns weight that needs to be accounted when receiving confirmations for given a number of
	/// messages with delivery confirmation transaction (`receive_messages_delivery_proof`).
	fn receive_messages_delivery_proof_messages_overhead(messages: MessageNonce) -> Weight {
		let weight_of_two_messages =
			Self::receive_delivery_proof_for_two_messages_by_single_relayer();
		let weight_of_single_message = Self::receive_delivery_proof_for_single_message();
		weight_of_two_messages
			.saturating_sub(weight_of_single_message)
			.saturating_mul(messages as _)
	}

	/// Returns weight that needs to be accounted when receiving confirmations for given a number of
	/// relayers entries with delivery confirmation transaction (`receive_messages_delivery_proof`).
	fn receive_messages_delivery_proof_relayers_overhead(relayers: MessageNonce) -> Weight {
		let weight_of_two_messages_by_two_relayers =
			Self::receive_delivery_proof_for_two_messages_by_two_relayers();
		let weight_of_two_messages_by_single_relayer =
			Self::receive_delivery_proof_for_two_messages_by_single_relayer();
		weight_of_two_messages_by_two_relayers
			.saturating_sub(weight_of_two_messages_by_single_relayer)
			.saturating_mul(relayers as _)
	}

	/// Returns weight that needs to be accounted when storage proof of given size is received
	/// (either in `receive_messages_proof` or `receive_messages_delivery_proof`).
	///
	/// **IMPORTANT**: this overhead is already included in the 'base' transaction cost - e.g. proof
	/// size depends on messages count or number of entries in the unrewarded relayers set. So this
	/// shouldn't be added to cost of transaction, but instead should act as a minimal cost that the
	/// relayer must pay when it relays proof of given size (even if cost based on other parameters
	/// is less than that cost).
	fn storage_proof_size_overhead(proof_size: u32) -> Weight {
		let proof_size_in_bytes = proof_size;
		let byte_weight = Self::receive_single_n_bytes_message_proof(2) -
			Self::receive_single_n_bytes_message_proof(1);
		proof_size_in_bytes * byte_weight
	}

	// Functions that may be used by runtime developers.

	/// Returns dispatch weight of message of given size.
	///
	/// This function would return correct value only if your runtime is configured to run
	/// `receive_single_message_proof_with_dispatch` benchmark. See its requirements for
	/// details.
	fn message_dispatch_weight(message_size: u32) -> Weight {
		let message_size_in_bytes = message_size;
		Self::receive_single_n_bytes_message_proof_with_dispatch(message_size_in_bytes)
			.saturating_sub(Self::receive_single_n_bytes_message_proof(message_size_in_bytes))
	}
}

impl WeightInfoExt for () {
	fn expected_extra_storage_proof_size() -> u32 {
		EXTRA_STORAGE_PROOF_SIZE
	}

	fn receive_messages_proof_overhead_from_runtime() -> Weight {
		Weight::zero()
	}

	fn receive_messages_delivery_proof_overhead_from_runtime() -> Weight {
		Weight::zero()
	}
}

impl<T: frame_system::Config> WeightInfoExt for crate::weights::BridgeWeight<T> {
	fn expected_extra_storage_proof_size() -> u32 {
		EXTRA_STORAGE_PROOF_SIZE
	}

	fn receive_messages_proof_overhead_from_runtime() -> Weight {
		Weight::zero()
	}

	fn receive_messages_delivery_proof_overhead_from_runtime() -> Weight {
		Weight::zero()
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use crate::{tests::mock::TestRuntime, weights::BridgeWeight};

	#[test]
	fn ensure_default_weights_are_correct() {
		ensure_weights_are_correct::<BridgeWeight<TestRuntime>>();
	}
}