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// Copyright 2018 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/>.
//! Bridge between the network and consensus service for getting collations to it.
use polkadot_primitives::Hash;
use polkadot_primitives::parachain::{CollatorId, Id as ParaId, Collation};
use futures::sync::oneshot;
use std::collections::hash_map::{HashMap, Entry};
use std::time::{Duration, Instant};
const COLLATION_LIFETIME: Duration = Duration::from_secs(60 * 5);
/// The role of the collator. Whether they're the primary or backup for this parachain.
#[derive(PartialEq, Debug, Clone, Copy, Encode, Decode)]
pub enum Role {
/// Primary collators should send collations whenever it's time.
/// Backup collators should not.
/// A maintenance action for the collator set.
#[derive(PartialEq, Debug)]
#[allow(dead_code)]
pub enum Action {
/// Disconnect the given collator.
/// Give the collator a new role.
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}
struct CollationSlot {
live_at: Instant,
entries: SlotEntries,
}
impl CollationSlot {
fn blank_now() -> Self {
CollationSlot {
live_at: Instant::now(),
entries: SlotEntries::Blank,
}
}
fn stay_alive(&self, now: Instant) -> bool {
self.live_at + COLLATION_LIFETIME > now
}
}
enum SlotEntries {
Blank,
// not queried yet
Pending(Vec<Collation>),
// waiting for next to arrive.
Awaiting(Vec<oneshot::Sender<Collation>>),
}
impl SlotEntries {
fn received_collation(&mut self, collation: Collation) {
*self = match ::std::mem::replace(self, SlotEntries::Blank) {
SlotEntries::Blank => SlotEntries::Pending(vec![collation]),
SlotEntries::Pending(mut cs) => {
cs.push(collation);
SlotEntries::Pending(cs)
}
SlotEntries::Awaiting(senders) => {
for sender in senders {
let _ = sender.send(collation.clone());
}
SlotEntries::Blank
}
};
}
fn await_with(&mut self, sender: oneshot::Sender<Collation>) {
*self = match ::std::mem::replace(self, SlotEntries::Blank) {
SlotEntries::Blank => SlotEntries::Awaiting(vec![sender]),
SlotEntries::Awaiting(mut senders) => {
senders.push(sender);
SlotEntries::Awaiting(senders)
}
SlotEntries::Pending(mut cs) => {
let next_collation = cs.pop().expect("empty variant is always `Blank`; qed");
let _ = sender.send(next_collation);
if cs.is_empty() {
SlotEntries::Blank
} else {
SlotEntries::Pending(cs)
}
}
};
}
}
struct ParachainCollators {
primary: CollatorId,
backup: Vec<CollatorId>,
}
/// Manages connected collators and role assignments from the perspective of a validator.
pub struct CollatorPool {
parachain_collators: HashMap<ParaId, ParachainCollators>,
collations: HashMap<(Hash, ParaId), CollationSlot>,
}
impl CollatorPool {
/// Create a new `CollatorPool` object.
pub fn new() -> Self {
CollatorPool {
collators: HashMap::new(),
parachain_collators: HashMap::new(),
collations: HashMap::new(),
}
}
/// Call when a new collator is authenticated. Returns the role.
pub fn on_new_collator(&mut self, collator_id: CollatorId, para_id: ParaId) -> Role {
self.collators.insert(collator_id.clone(), para_id);
match self.parachain_collators.entry(para_id) {
Entry::Vacant(vacant) => {
vacant.insert(ParachainCollators {
backup: Vec::new(),
});
Role::Primary
},
Entry::Occupied(mut occupied) => {
occupied.get_mut().backup.push(collator_id);
Role::Backup
}
}
}
/// Called when a collator disconnects. If it was the primary, returns a new primary for that
/// parachain.
pub fn on_disconnect(&mut self, collator_id: CollatorId) -> Option<CollatorId> {
self.collators.remove(&collator_id).and_then(|para_id| match self.parachain_collators.entry(para_id) {
Entry::Vacant(_) => None,
Entry::Occupied(mut occ) => {
if occ.get().backup.is_empty() {
occ.remove();
None
} else {
let mut collators = occ.get_mut();
collators.primary = collators.backup.pop().expect("backup non-empty; qed");
let pos = occ.get().backup.iter().position(|a| a == &collator_id)
.expect("registered collator always present in backup if not primary; qed");
occ.get_mut().backup.remove(pos);
None
}
}
})
}
/// Called when a collation is received.
/// The collator should be registered for the parachain of the collation as a precondition of this function.
/// The collation should have been checked for integrity of signature before passing to this function.
pub fn on_collation(&mut self, collator_id: CollatorId, relay_parent: Hash, collation: Collation) {
if let Some(para_id) = self.collators.get(&collator_id) {
debug_assert_eq!(para_id, &collation.receipt.parachain_index);
// TODO: punish if not primary? (https://github.com/paritytech/polkadot/issues/213)
self.collations.entry((relay_parent, para_id.clone()))
.or_insert_with(CollationSlot::blank_now)
.entries
.received_collation(collation);
}
}
/// Wait for a collation from a parachain.
pub fn await_collation(&mut self, relay_parent: Hash, para_id: ParaId, sender: oneshot::Sender<Collation>) {
self.collations.entry((relay_parent, para_id))
.or_insert_with(CollationSlot::blank_now)
.entries
.await_with(sender);
}
/// Call periodically to perform collator set maintenance.
/// Returns a set of actions to perform on the network level.
pub fn maintain_peers(&mut self) -> Vec<Action> {
// TODO: rearrange periodically to new primary, evaluate based on latency etc.
// https://github.com/paritytech/polkadot/issues/214
Vec::new()
}
/// called when a block with given hash has been imported.
pub fn collect_garbage(&mut self, chain_head: Option<&Hash>) {
let now = Instant::now();
self.collations.retain(|&(ref h, _), slot| chain_head != Some(h) && slot.stay_alive(now));
}
}
#[cfg(test)]
mod tests {
use super::*;
use substrate_primitives::crypto::UncheckedInto;
use polkadot_primitives::parachain::{CandidateReceipt, BlockData, HeadData};
use futures::Future;
#[test]
fn disconnect_primary_gives_new_primary() {
let mut pool = CollatorPool::new();
let para_id: ParaId = 5.into();
let bad_primary: CollatorId = [0; 32].unchecked_into();
let good_backup: CollatorId = [1; 32].unchecked_into();
assert_eq!(pool.on_new_collator(bad_primary.clone(), para_id.clone()), Role::Primary);
assert_eq!(pool.on_new_collator(good_backup.clone(), para_id.clone()), Role::Backup);
assert_eq!(pool.on_disconnect(bad_primary), Some(good_backup.clone()));
assert_eq!(pool.on_disconnect(good_backup), None);
}
#[test]
fn disconnect_backup_removes_from_pool() {
let mut pool = CollatorPool::new();
let para_id: ParaId = 5.into();
let primary = [0; 32].unchecked_into();
let backup: CollatorId = [1; 32].unchecked_into();
assert_eq!(pool.on_new_collator(primary, para_id.clone()), Role::Primary);
assert_eq!(pool.on_new_collator(backup.clone(), para_id.clone()), Role::Backup);
assert_eq!(pool.on_disconnect(backup), None);
assert!(pool.parachain_collators.get(¶_id).unwrap().backup.is_empty());
}
#[test]
fn await_before_collation() {
let mut pool = CollatorPool::new();
let para_id: ParaId = 5.into();
let primary: CollatorId = [0; 32].unchecked_into();
let relay_parent = [1; 32].into();
assert_eq!(pool.on_new_collator(primary.clone(), para_id.clone()), Role::Primary);
let (tx1, rx1) = oneshot::channel();
let (tx2, rx2) = oneshot::channel();
pool.await_collation(relay_parent, para_id, tx1);
pool.await_collation(relay_parent, para_id, tx2);
pool.on_collation(primary.clone(), relay_parent, Collation {
receipt: CandidateReceipt {
parachain_index: para_id,
collator: primary.into(),
head_data: HeadData(vec![1, 2, 3]),
balance_uploads: vec![],
egress_queue_roots: vec![],
fees: 0,
block_data_hash: [3; 32].into(),
},
block_data: BlockData(vec![4, 5, 6]),
});
rx1.wait().unwrap();
rx2.wait().unwrap();
}
#[test]
fn collate_before_await() {
let mut pool = CollatorPool::new();
let para_id: ParaId = 5.into();
let primary: CollatorId = [0; 32].unchecked_into();
let relay_parent = [1; 32].into();
assert_eq!(pool.on_new_collator(primary.clone(), para_id.clone()), Role::Primary);
pool.on_collation(primary.clone(), relay_parent, Collation {
receipt: CandidateReceipt {
parachain_index: para_id,
collator: primary,
signature: Default::default(),
head_data: HeadData(vec![1, 2, 3]),
balance_uploads: vec![],
egress_queue_roots: vec![],
fees: 0,
block_data_hash: [3; 32].into(),
},
block_data: BlockData(vec![4, 5, 6]),
});
let (tx, rx) = oneshot::channel();
pool.await_collation(relay_parent, para_id, tx);
rx.wait().unwrap();
}
#[test]
fn slot_stay_alive() {
let slot = CollationSlot::blank_now();
let now = slot.live_at;
assert!(slot.stay_alive(now));
assert!(slot.stay_alive(now + Duration::from_secs(10)));
assert!(!slot.stay_alive(now + COLLATION_LIFETIME));
assert!(!slot.stay_alive(now + COLLATION_LIFETIME + Duration::from_secs(10)));
}
}