Fix ordering of latest_top_ups (#7046)

backend/canisters/cycles_dispenser/CHANGELOG.md

@@ -10,6 +10,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 - Expose size of each virtual stable memory in metrics ([#6981](https://github.com/open-chat-labs/open-chat/pull/6981))
 
+### Fixed
+
+- Fix ordering of `latest_top_ups` ([#7046](https://github.com/open-chat-labs/open-chat/pull/7046))
+
 ## [[2.0.1485](https://github.com/open-chat-labs/open-chat/releases/tag/v2.0.1485-cycles_dispenser)] - 2024-11-29
 
 ### Added

backend/canisters/cycles_dispenser/impl/src/model/canisters.rs

@@ -1,5 +1,6 @@
 use candid::CandidType;
 use serde::{Deserialize, Serialize};
+use std::cmp::Reverse;
 use std::collections::hash_map::Entry::Vacant;
 use std::collections::{BinaryHeap, HashMap};
 use types::{CanisterId, Cycles, TimestampMillis};
@@ -67,14 +68,17 @@ impl Canisters {
             })
         }) {
             if heap.len() < count {
-                heap.push(top_up);
-            } else if top_up > *heap.peek().unwrap() {
+                heap.push(Reverse(top_up));
+            } else if top_up > heap.peek().unwrap().0 {
                 heap.pop();
-                heap.push(top_up);
+                heap.push(Reverse(top_up));
             }
         }
 
-        let mut vec = heap.into_sorted_vec();
+        let mut vec = Vec::with_capacity(heap.len());
+        while let Some(Reverse(top_up)) = heap.pop() {
+            vec.push(top_up);
+        }
         vec.reverse();
         vec
     }