From b62df82c4383ac4c61ea0c83becd656696f28f4c Mon Sep 17 00:00:00 2001
From: Lucas Meier <lucas@cronokirby.com>
Date: Tue, 24 Oct 2023 19:13:38 -0700
Subject: [PATCH] Summonerd: implement per-address deduplication in queue

(necessary with recent modifications)
---
 tools/summonerd/src/queue.rs | 158 +++++++++++++++++++++++++++++++++++
 1 file changed, 158 insertions(+)
 create mode 100644 tools/summonerd/src/queue.rs

diff --git a/tools/summonerd/src/queue.rs b/tools/summonerd/src/queue.rs
new file mode 100644
index 0000000000..c60385693d
--- /dev/null
+++ b/tools/summonerd/src/queue.rs
@@ -0,0 +1,158 @@
+use anyhow::Result;
+use std::{collections::HashSet, sync::Arc};
+
+use penumbra_keys::Address;
+use penumbra_num::Amount;
+use tokio::sync::RwLock;
+
+use crate::participant::Participant;
+
+/// The inner struct for "normal" manipulation outside of the concurrent data structure
+struct Inner {
+    // Invariant: this is always sorted by the amount.
+    // Invariant: no two participants have the same address
+    sorted: Vec<(Participant, Amount)>,
+    // Used to keep track of all the addresses in the sorted vec.
+    addresses: HashSet<Address>,
+}
+
+impl Inner {
+    fn new() -> Self {
+        Inner {
+            sorted: Vec::new(),
+            addresses: HashSet::new(),
+        }
+    }
+
+    /// Get the number of participants in the queue
+    fn len(&self) -> usize {
+        self.sorted.len()
+    }
+
+    /// Insert a participant and their bid into the queue.
+    ///
+    /// If the participant is already in the queue (as determined by having the same address),
+    /// then this may push them higher in the queue if the bid is higher.
+    ///
+    /// Their bid being lower should never happen in practice.
+    ///
+    /// We also don't expect the case of duplicate participants to happen either, but we should
+    /// handle it.
+    fn push(&mut self, participant: Participant, bid: Amount) {
+        let address = participant.address();
+        // If the participant is already present in the queue, remove them.
+        if self.addresses.contains(&address) {
+            // Note, we don't remove them from the address list, because we'll be inserting soon.
+            self.sorted.retain(|(p, _)| p.address() != address);
+        }
+        let position = match self.sorted.binary_search_by(|(_, a)| a.cmp(&bid)) {
+            // If we find a participant with the same bid, insert before them.
+            Ok(pos) => pos,
+            // If no participant with the bid is found, this is the correct position.
+            Err(pos) => pos,
+        };
+        self.sorted.insert(position, (participant, bid));
+        self.addresses.insert(address);
+    }
+
+    /// Remove all participants that aren't live
+    fn prune(&mut self) {
+        self.sorted.retain(|(participant, _)| {
+            let live = participant.is_live();
+            // Make sure to remove from the addresses list as well.
+            if !live {
+                self.addresses.remove(&participant.address());
+            }
+            live
+        })
+    }
+
+    /// Remove the participant with the highest bid from this queue.
+    ///
+    /// This will return None if the queue is empty.
+    fn pop(&mut self) -> Option<(Participant, Amount)> {
+        let result = self.sorted.pop();
+        if let Some((ref participant, _)) = result {
+            self.addresses.remove(&participant.address());
+        }
+        result
+    }
+
+    /// Return the highest bid in the queue, if not empty.
+    ///
+    /// This will return None if the queue is empty.
+    fn top_bid(&self) -> Option<Amount> {
+        // The last item in the sorted vec will have the highest bid, use that.
+        self.sorted.last().map(|(_, amount)| *amount)
+    }
+
+    /// Return participants, and their bids, in ascending order of bids.
+    fn iter(&self) -> impl Iterator<Item = &(Participant, Amount)> {
+        self.sorted.iter()
+    }
+}
+
+/// A thread safe queue of participants, sorted by bid amounts.
+#[derive(Clone)]
+pub struct ParticipantQueue {
+    participants: Arc<RwLock<Inner>>,
+}
+
+impl ParticipantQueue {
+    pub fn new() -> Self {
+        Self {
+            participants: Arc::new(RwLock::new(Inner::new())),
+        }
+    }
+
+    /// Get the length of the queue
+    pub async fn len(&self) -> usize {
+        self.participants.read().await.len()
+    }
+
+    /// Push a new participant into the queue, given their bid.
+    pub async fn push(&self, participant: Participant, bid: Amount) {
+        self.participants.write().await.push(participant, bid);
+    }
+
+    /// Remove inactive connections, and then remove out the highest bidder.
+    pub async fn prune_and_pop(&self) -> Option<(Participant, Amount)> {
+        let mut participants = self.participants.write().await;
+        participants.prune();
+        participants.pop()
+    }
+
+    #[tracing::instrument(skip(self))]
+    async fn inform(&self, filter: Option<Address>) -> Result<()> {
+        let participants = self.participants.read().await;
+        let top_bid = match participants.top_bid() {
+            None => return Ok(()),
+            Some(bid) => bid,
+        };
+        let participant_count = participants.len();
+        for (i, (participant, bid)) in participants.iter().enumerate() {
+            let address = participant.address();
+            match filter {
+                Some(f) if f != address => continue,
+                _ => {}
+            }
+            // Ignore failures (besides logging), let pruning happen later.
+            if let Err(e) =
+                participant.try_notify(i as u32, participant_count as u32, top_bid, *bid)
+            {
+                tracing::debug!(?address, ?e, "failed to notify");
+            }
+        }
+        Ok(())
+    }
+
+    /// Inform one participant of their position in the queue.
+    pub async fn inform_one(&self, address: Address) -> Result<()> {
+        self.inform(Some(address)).await
+    }
+
+    /// Informal all participants of their position in the queue.
+    pub async fn inform_all(&self) -> Result<()> {
+        self.inform(None).await
+    }
+}