From f35a6a8be0fec579957746ebf67bfb8e46ec7aba Mon Sep 17 00:00:00 2001
From: behzad nouri <behzadnouri@gmail.com>
Date: Wed, 14 Apr 2021 18:45:20 +0000
Subject: [PATCH] prioritizes contact-infos in pull responses (#16541)

Expired crds values where the contact-info does not exist are wasted:
https://github.com/solana-labs/solana/blob/f804ce63c/core/src/crds_gossip_pull.rs#L353-L378
and then are sent again over the next pull-request.

Also, the stake of the first response (which can be anything) is used to
weight all pull-responses to a node, while the rest of responses can
have different stake.
https://github.com/solana-labs/solana/blob/f804ce63c/core/src/cluster_info.rs#L2231
---
 core/src/cluster_info.rs | 61 ++++++++++++++++++----------------------
 1 file changed, 28 insertions(+), 33 deletions(-)

diff --git a/core/src/cluster_info.rs b/core/src/cluster_info.rs
index c13115f55b..b60b5240e0 100644
--- a/core/src/cluster_info.rs
+++ b/core/src/cluster_info.rs
@@ -27,9 +27,7 @@ use crate::{
     result::{Error, Result},
     weighted_shuffle::weighted_shuffle,
 };
-use rand::distributions::{Distribution, WeightedIndex};
-use rand::{CryptoRng, Rng, SeedableRng};
-use rand_chacha::ChaChaRng;
+use rand::{CryptoRng, Rng};
 use solana_ledger::shred::Shred;
 use solana_sdk::sanitize::{Sanitize, SanitizeError};
 
@@ -2224,42 +2222,41 @@ impl ClusterInfo {
             return packets;
         }
 
-        let mut stats: Vec<_> = pull_responses
+        let stats: Vec<_> = pull_responses
             .iter()
             .enumerate()
             .map(|(i, (responses, _from_addr))| {
-                let score: u64 = if stakes.get(&responses[0].pubkey()).is_some() {
-                    2
-                } else {
-                    1
-                };
                 responses
                     .iter()
                     .enumerate()
-                    .map(|(j, _response)| ResponseScore {
-                        to: i,
-                        responses_index: j,
-                        score,
+                    .map(|(j, response)| {
+                        let score = if stakes.contains_key(&response.pubkey()) {
+                            2
+                        } else {
+                            1
+                        };
+                        let score = match response.data {
+                            CrdsData::ContactInfo(_) => 2 * score,
+                            _ => score,
+                        };
+                        ResponseScore {
+                            to: i,
+                            responses_index: j,
+                            score,
+                        }
                     })
                     .collect::<Vec<ResponseScore>>()
             })
             .flatten()
             .collect();
 
-        stats.sort_by(|a, b| a.score.cmp(&b.score));
+        let mut seed = [0; 32];
+        rand::thread_rng().fill(&mut seed[..]);
         let weights: Vec<_> = stats.iter().map(|stat| stat.score).collect();
 
-        let seed = [48u8; 32];
-        let rng = &mut ChaChaRng::from_seed(seed);
-        let weighted_index = WeightedIndex::new(weights).unwrap();
-
         let mut total_bytes = 0;
-        let mut sent = HashSet::new();
-        while sent.len() < stats.len() {
-            let index = weighted_index.sample(rng);
-            if sent.contains(&index) {
-                continue;
-            }
+        let mut sent = 0;
+        for index in weighted_shuffle(&weights, seed) {
             let stat = &stats[index];
             let from_addr = pull_responses[stat.to].1;
             let response = pull_responses[stat.to].0[stat.responses_index].clone();
@@ -2268,9 +2265,9 @@ impl ClusterInfo {
                 Err(err) => error!("failed to write pull-response packet: {:?}", err),
                 Ok(packet) => {
                     if self.outbound_budget.take(packet.meta.size) {
-                        sent.insert(index);
                         total_bytes += packet.meta.size;
-                        packets.packets.push(packet)
+                        packets.packets.push(packet);
+                        sent += 1;
                     } else {
                         inc_new_counter_info!("gossip_pull_request-no_budget", 1);
                         break;
@@ -2279,15 +2276,12 @@ impl ClusterInfo {
             }
         }
         time.stop();
-        inc_new_counter_info!("gossip_pull_request-sent_requests", sent.len());
-        inc_new_counter_info!(
-            "gossip_pull_request-dropped_requests",
-            stats.len() - sent.len()
-        );
+        inc_new_counter_info!("gossip_pull_request-sent_requests", sent);
+        inc_new_counter_info!("gossip_pull_request-dropped_requests", stats.len() - sent);
         debug!(
             "handle_pull_requests: {} sent: {} total: {} total_bytes: {}",
             time,
-            sent.len(),
+            sent,
             stats.len(),
             total_bytes
         );
@@ -3467,7 +3461,8 @@ mod tests {
         duplicate_shred::{self, tests::new_rand_shred, MAX_DUPLICATE_SHREDS},
     };
     use itertools::izip;
-    use rand::seq::SliceRandom;
+    use rand::{seq::SliceRandom, SeedableRng};
+    use rand_chacha::ChaChaRng;
     use serial_test::serial;
     use solana_ledger::shred::Shredder;
     use solana_sdk::signature::{Keypair, Signer};