Add randomization in sync retry batch peer selection (#5822)

* Add randomization in sync retry batch peer selection

* Use min

* Apply suggestions from code review

Co-authored-by: João Oliveira <[email protected]>

* Merge branch 'unstable' into peer-prio

Author: dapplion

beacon_node/network/src/sync/backfill_sync/mod.rs

@@ -919,24 +919,22 @@ impl<T: BeaconChainTypes> BackFillSync<T> {
         // Find a peer to request the batch
         let failed_peers = batch.failed_peers();
 
-        let new_peer = {
-            let mut priorized_peers = self
-                .network_globals
-                .peers
-                .read()
-                .synced_peers()
-                .map(|peer| {
-                    (
-                        failed_peers.contains(peer),
-                        self.active_requests.get(peer).map(|v| v.len()).unwrap_or(0),
-                        *peer,
-                    )
-                })
-                .collect::<Vec<_>>();
+        let new_peer = self
+            .network_globals
+            .peers
+            .read()
+            .synced_peers()
+            .map(|peer| {
+                (
+                    failed_peers.contains(peer),
+                    self.active_requests.get(peer).map(|v| v.len()).unwrap_or(0),
+                    rand::random::<u32>(),
+                    *peer,
+                )
+            })
             // Sort peers prioritizing unrelated peers with less active requests.
-            priorized_peers.sort_unstable();
-            priorized_peers.first().map(|&(_, _, peer)| peer)
-        };
+            .min()
+            .map(|(_, _, _, peer)| peer);
 
         if let Some(peer) = new_peer {
             self.participating_peers.insert(peer);

beacon_node/network/src/sync/range_sync/chain.rs

@@ -7,7 +7,7 @@ use beacon_chain::BeaconChainTypes;
 use fnv::FnvHashMap;
 use lighthouse_network::service::api_types::Id;
 use lighthouse_network::{PeerAction, PeerId};
-use rand::seq::SliceRandom;
+use rand::{seq::SliceRandom, Rng};
 use slog::{crit, debug, o, warn};
 use std::collections::{btree_map::Entry, BTreeMap, HashSet};
 use std::hash::{Hash, Hasher};
@@ -873,16 +873,20 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
         // Find a peer to request the batch
         let failed_peers = batch.failed_peers();
 
-        let new_peer = {
-            let mut priorized_peers = self
-                .peers
-                .iter()
-                .map(|(peer, requests)| (failed_peers.contains(peer), requests.len(), *peer))
-                .collect::<Vec<_>>();
+        let new_peer = self
+            .peers
+            .iter()
+            .map(|(peer, requests)| {
+                (
+                    failed_peers.contains(peer),
+                    requests.len(),
+                    rand::thread_rng().gen::<u32>(),
+                    *peer,
+                )
+            })
             // Sort peers prioritizing unrelated peers with less active requests.
-            priorized_peers.sort_unstable();
-            priorized_peers.first().map(|&(_, _, peer)| peer)
-        };
+            .min()
+            .map(|(_, _, _, peer)| peer);
 
         if let Some(peer) = new_peer {
             self.send_batch(network, batch_id, peer)