From f79c9d40944580afa565b8539ead7fd9928f3f20 Mon Sep 17 00:00:00 2001
From: behzad nouri <behzadnouri@gmail.com>
Date: Tue, 16 Feb 2021 21:12:13 +0000
Subject: [PATCH] adds an upper bound on cluster-slots size (#15300)

https://github.com/solana-labs/solana/issues/14366#issuecomment-769096305
---
 core/src/cluster_slots.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/core/src/cluster_slots.rs b/core/src/cluster_slots.rs
index f016169586..2a93354a0f 100644
--- a/core/src/cluster_slots.rs
+++ b/core/src/cluster_slots.rs
@@ -9,6 +9,10 @@ use std::{
     sync::{Arc, RwLock},
 };
 
+// Limit the size of cluster-slots map in case
+// of receiving bogus epoch slots values.
+const CLUSTER_SLOTS_TRIM_SIZE: usize = 524_288; // 512K
+
 pub type SlotPubkeys = HashMap<Pubkey, u64>;
 
 #[derive(Default)]
@@ -43,6 +47,12 @@ impl ClusterSlots {
         {
             let mut cluster_slots = self.cluster_slots.write().unwrap();
             *cluster_slots = cluster_slots.split_off(&(root + 1));
+            // Trimming is done at 2x size so that amortized it has a constant
+            // cost. The slots furthest away from the root are discarded.
+            if cluster_slots.len() > 2 * CLUSTER_SLOTS_TRIM_SIZE {
+                let key = *cluster_slots.keys().nth(CLUSTER_SLOTS_TRIM_SIZE).unwrap();
+                cluster_slots.split_off(&key);
+            }
         }
         *self.since.write().unwrap() = since;
     }