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Improve readability of vote lockout processing (#16987)

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* Improve readability of vote lockout processing

* clippy

* simplify comment

* feedback
This commit is contained in:
Justin Starry
2021-05-02 16:36:06 +08:00
committed by GitHub
parent 643133b2c1
commit 8e561354d5
2 changed files with 36 additions and 24 deletions
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39
programs/vote/src/vote_state/mod.rs
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@ -84,13 +84,15 @@ impl Lockout {
(INITIAL_LOCKOUT as u64).pow(self.confirmation_count)
}
// The slot height at which this vote expires (cannot vote for any slot
// less than this)
pub fn expiration_slot(&self) -> Slot {
// The last slot at which a vote is still locked out. Validators should not
// vote on a slot in another fork which is less than or equal to this slot
// to avoid having their stake slashed.
pub fn last_locked_out_slot(&self) -> Slot {
self.slot + self.lockout()
}
pub fn is_expired(&self, slot: Slot) -> bool {
self.expiration_slot() < slot
pub fn is_locked_out_at_slot(&self, slot: Slot) -> bool {
self.last_locked_out_slot() >= slot
}
}
@ -354,22 +356,24 @@ impl VoteState {
}
self.check_slots_are_valid(vote, slot_hashes)?;
vote.slots.iter().for_each(|s| self.process_slot(*s, epoch));
vote.slots
.iter()
.for_each(|s| self.process_next_vote_slot(*s, epoch));
Ok(())
}
pub fn process_slot(&mut self, slot: Slot, epoch: Epoch) {
pub fn process_next_vote_slot(&mut self, next_vote_slot: Slot, epoch: Epoch) {
// Ignore votes for slots earlier than we already have votes for
if self
.last_voted_slot()
.map_or(false, |last_voted_slot| slot <= last_voted_slot)
.map_or(false, |last_voted_slot| next_vote_slot <= last_voted_slot)
{
return;
}
let vote = Lockout::new(slot);
let vote = Lockout::new(next_vote_slot);
self.pop_expired_votes(slot);
self.pop_expired_votes(next_vote_slot);
// Once the stack is full, pop the oldest lockout and distribute rewards
if self.votes.len() == MAX_LOCKOUT_HISTORY {
@ -540,9 +544,13 @@ impl VoteState {
Ok(pubkey)
}
fn pop_expired_votes(&mut self, slot: Slot) {
loop {
if self.last_lockout().map_or(false, |v| v.is_expired(slot)) {
// Pop all recent votes that are not locked out at the next vote slot. This
// allows validators to switch forks once their votes for another fork have
// expired. This also allows validators continue voting on recent blocks in
// the same fork without increasing lockouts.
fn pop_expired_votes(&mut self, next_vote_slot: Slot) {
while let Some(vote) = self.last_lockout() {
if !vote.is_locked_out_at_slot(next_vote_slot) {
self.votes.pop_back();
} else {
break;
@ -1350,11 +1358,12 @@ mod tests {
// second vote
let top_vote = vote_state.votes.front().unwrap().slot;
vote_state
.process_slot_vote_unchecked(vote_state.last_lockout().unwrap().expiration_slot());
.process_slot_vote_unchecked(vote_state.last_lockout().unwrap().last_locked_out_slot());
assert_eq!(Some(top_vote), vote_state.root_slot);
// Expire everything except the first vote
vote_state.process_slot_vote_unchecked(vote_state.votes.front().unwrap().expiration_slot());
vote_state
.process_slot_vote_unchecked(vote_state.votes.front().unwrap().last_locked_out_slot());
// First vote and new vote are both stored for a total of 2 votes
assert_eq!(vote_state.votes.len(), 2);
}