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use crate::{config::TangleConfig, storage::StorageBackend, tangle::Tangle};
use bee_message::MessageId;
use hashbrown::{hash_map::Entry, HashMap, HashSet};
use log::debug;
use rand::seq::IteratorRandom;
use std::time::Instant;
#[allow(clippy::enum_variant_names)]
enum Score {
NonLazy,
SemiLazy,
Lazy,
}
const YMRSI_DELTA: u32 = 8;
const OMRSI_DELTA: u32 = 13;
const MAX_LIMIT_NON_LAZY: u8 = 100;
const MAX_AGE_SECONDS_AFTER_FIRST_CHILD: u8 = 3;
const MAX_NUM_CHILDREN: u8 = 2;
#[derive(Default)]
struct TipMetadata {
children: HashSet<MessageId>,
time_first_child: Option<Instant>,
}
impl TipMetadata {
pub(crate) fn new() -> Self {
Self::default()
}
}
pub(crate) struct UrtsTipPool {
tips: HashMap<MessageId, TipMetadata>,
non_lazy_tips: HashSet<MessageId>,
below_max_depth: u32,
}
impl UrtsTipPool {
pub(crate) fn new(config: &TangleConfig) -> Self {
Self {
tips: HashMap::default(),
non_lazy_tips: HashSet::default(),
below_max_depth: config.below_max_depth(),
}
}
pub(crate) fn non_lazy_tips(&self) -> &HashSet<MessageId> {
&self.non_lazy_tips
}
pub(crate) async fn insert<B: StorageBackend>(
&mut self,
tangle: &Tangle<B>,
message_id: MessageId,
parents: Vec<MessageId>,
) {
if let Score::NonLazy = self.tip_score::<B>(tangle, &message_id).await {
self.non_lazy_tips.insert(message_id);
self.tips.insert(message_id, TipMetadata::new());
for parent in &parents {
self.add_child(*parent, message_id);
self.check_retention_rules_for_parent(parent);
}
}
}
fn add_child(&mut self, parent: MessageId, child: MessageId) {
match self.tips.entry(parent) {
Entry::Occupied(mut entry) => {
let metadata = entry.get_mut();
metadata.children.insert(child);
if metadata.time_first_child == None {
metadata.time_first_child = Some(Instant::now());
}
}
Entry::Vacant(entry) => {
let mut metadata = TipMetadata::new();
metadata.children.insert(child);
metadata.time_first_child = Some(Instant::now());
entry.insert(metadata);
}
}
}
fn check_retention_rules_for_parent(&mut self, parent: &MessageId) {
if self.non_lazy_tips.len() > MAX_LIMIT_NON_LAZY as usize
|| self.tips.get(parent).unwrap().children.len() > MAX_NUM_CHILDREN as usize
|| self
.tips
.get(parent)
.unwrap()
.time_first_child
.unwrap()
.elapsed()
.as_secs()
> MAX_AGE_SECONDS_AFTER_FIRST_CHILD as u64
{
self.tips.remove(parent);
self.non_lazy_tips.remove(parent);
}
}
pub(crate) async fn update_scores<B: StorageBackend>(&mut self, tangle: &Tangle<B>) {
let mut to_remove = Vec::new();
for tip in self.tips.keys() {
match self.tip_score::<B>(tangle, tip).await {
Score::SemiLazy | Score::Lazy => {
to_remove.push(*tip);
}
_ => continue,
}
}
for tip in to_remove {
self.tips.remove(&tip);
self.non_lazy_tips.remove(&tip);
}
debug!("Non-lazy tips {}", self.non_lazy_tips.len());
}
async fn tip_score<B: StorageBackend>(&self, tangle: &Tangle<B>, message_id: &MessageId) -> Score {
if !tangle.contains(message_id).await {
Score::Lazy
} else {
let smi = *tangle.get_solid_milestone_index();
let omrsi = *tangle.omrsi(message_id).await.unwrap().index();
let ymrsi = *tangle.ymrsi(message_id).await.unwrap().index();
if smi > ymrsi + YMRSI_DELTA || smi > omrsi + self.below_max_depth {
Score::Lazy
} else if smi > omrsi + OMRSI_DELTA {
Score::SemiLazy
} else {
Score::NonLazy
}
}
}
pub fn choose_non_lazy_tips(&self) -> Option<Vec<MessageId>> {
if self.non_lazy_tips.is_empty() {
None
} else {
Some(if self.non_lazy_tips.len() < self.optimal_num_tips() {
self.non_lazy_tips.iter().copied().collect()
} else {
self.non_lazy_tips
.iter()
.choose_multiple(&mut rand::thread_rng(), self.optimal_num_tips())
.iter()
.map(|t| **t)
.collect()
})
}
}
pub(crate) fn optimal_num_tips(&self) -> usize {
4
}
pub(crate) fn reduce_tips(&mut self) {
let non_lazy_tips = &mut self.non_lazy_tips;
self.tips.retain(|tip, metadata| {
metadata
.time_first_child
.filter(|age| age.elapsed().as_secs() > MAX_AGE_SECONDS_AFTER_FIRST_CHILD as u64)
.map(|_| non_lazy_tips.remove(tip))
.is_none()
});
}
}