120 lines
4.5 KiB
Rust
120 lines
4.5 KiB
Rust
// Copyright 2015-2018 Parity Technologies (UK) Ltd.
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// This file is part of Parity.
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// Parity is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// Parity is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with Parity. If not, see <http://www.gnu.org/licenses/>.
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//! Generic Transaction Pool
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//!
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//! An extensible and performant implementation of Ethereum Transaction Pool.
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//! The pool stores ordered, verified transactions according to some pluggable
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//! `Scoring` implementation.
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//! The pool also allows you to construct a set of `pending` transactions according
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//! to some notion of `Readiness` (pluggable).
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//!
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//! The pool is generic over transactions and should make no assumptions about them.
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//! The only thing we can rely on is the `Scoring` that defines:
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//! - the ordering of transactions from a single sender
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//! - the priority of the transaction compared to other transactions from different senders
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//!
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//! NOTE: the transactions from a single sender are not ordered by priority,
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//! but still when constructing pending set we always need to maintain the ordering
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//! (i.e. `txs[1]` always needs to be included after `txs[0]` even if it has higher priority)
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//!
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//! ### Design Details
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//!
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//! Performance assumptions:
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//! - Possibility to handle tens of thousands of transactions
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//! - Fast insertions and replacements `O(per-sender + log(senders))`
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//! - Reasonably fast removal of stalled transactions `O(per-sender)`
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//! - Reasonably fast construction of pending set `O(txs * (log(senders) + log(per-sender))`
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//!
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//! The removal performance could be improved by trading some memory. Currently `SmallVec` is used
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//! to store senders transactions, instead we could use `VecDeque` and efficiently `pop_front`
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//! the best transactions.
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//!
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//! The pending set construction and insertion complexity could be reduced by introducing
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//! a notion of `nonce` - an absolute, numeric ordering of transactions.
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//! We don't do that because of possible implications of EIP208 where nonce might not be
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//! explicitly available.
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//!
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//! 1. The pool groups transactions from particular sender together
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//! and stores them ordered by `Scoring` within that group
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//! i.e. `HashMap<Sender, Vec<Transaction>>`.
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//! 2. Additionaly we maintain the best and the worst transaction from each sender
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//! (by `Scoring` not `priority`) ordered by `priority`.
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//! It means that we can easily identify the best transaction inside the entire pool
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//! and the worst transaction.
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//! 3. Whenever new transaction is inserted to the queue:
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//! - first check all the limits (overall, memory, per-sender)
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//! - retrieve all transactions from a sender
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//! - binary search for position to insert the transaction
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//! - decide if we are replacing existing transaction (3 outcomes: drop, replace, insert)
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//! - update best and worst transaction from that sender if affected
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//! 4. Pending List construction:
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//! - Take the best transaction (by priority) from all senders to the List
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//! - Replace the transaction with next transaction (by ordering) from that sender (if any)
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//! - Repeat
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#![warn(missing_docs)]
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#[cfg(test)]
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mod tests;
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mod error;
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mod listener;
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mod options;
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mod pool;
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mod ready;
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mod replace;
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mod status;
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mod transactions;
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mod verifier;
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pub mod scoring;
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pub use self::{
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error::Error,
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listener::{Listener, NoopListener},
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options::Options,
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pool::{PendingIterator, Pool, Transaction, UnorderedIterator},
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ready::{Readiness, Ready},
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replace::{ReplaceTransaction, ShouldReplace},
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scoring::Scoring,
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status::{LightStatus, Status},
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verifier::Verifier,
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};
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use std::{fmt, hash::Hash};
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/// Already verified transaction that can be safely queued.
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pub trait VerifiedTransaction: fmt::Debug {
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/// Transaction hash type.
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type Hash: fmt::Debug + fmt::LowerHex + Eq + Clone + Hash;
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/// Transaction sender type.
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type Sender: fmt::Debug + Eq + Clone + Hash + Send;
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/// Transaction hash
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fn hash(&self) -> &Self::Hash;
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/// Memory usage
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fn mem_usage(&self) -> usize;
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/// Transaction sender
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fn sender(&self) -> &Self::Sender;
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/// Is it a service transaction?
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fn is_service(&self) -> bool;
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}
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