From b457df26e303ba4105b57988025d2f8fff7391e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Joakim=20Frosteg=C3=A5rd?= <joakim.frostegard@gmail.com>
Date: Thu, 9 Apr 2020 11:46:06 +0200
Subject: [PATCH] aquatic annonunce handler: downgrade TorrentMap ref instead
 of new .get

---
 aquatic/src/lib/handlers.rs                  | 98 ++++++++++----------
 aquatic_bench/src/bin/bench_handlers/main.rs |  6 +-
 2 files changed, 50 insertions(+), 54 deletions(-)

diff --git a/aquatic/src/lib/handlers.rs b/aquatic/src/lib/handlers.rs
index 443c8e0..f7a36d3 100644
--- a/aquatic/src/lib/handlers.rs
+++ b/aquatic/src/lib/handlers.rs
@@ -68,64 +68,60 @@ pub fn handle_announce_requests(
         let peer = Peer::from_announce_and_ip(&request, src.ip());
         let peer_status = peer.status;
 
-        let opt_removed_peer_status = {
-            let mut torrent_data = state.torrents
-                .entry(request.info_hash)
-                .or_insert_with(|| TorrentData::default());
-            
-            if peer_status == PeerStatus::Stopped {
-                torrent_data.peers.remove(&peer_key)
-                    .map(|peer| peer.status)
-            } else {
-                torrent_data.peers.insert(peer_key, peer)
-                    .map(|peer| peer.status)
-            }
+        let mut torrent_data = state.torrents
+            .entry(request.info_hash)
+            .or_default();
+        
+        let opt_removed_peer_status = if peer_status == PeerStatus::Stopped {
+            torrent_data.peers.remove(&peer_key)
+                .map(|peer| peer.status)
+        } else {
+            torrent_data.peers.insert(peer_key, peer)
+                .map(|peer| peer.status)
         };
 
+        // Downgrade ref since we don't need write access anymore, so that
+        // other threads can access torrent
+        let torrent_data = torrent_data.downgrade();
+
         let max_num_peers_to_take = (request.peers_wanted.0.max(0) as usize)
             .min(config.network.max_response_peers);
 
-        // Since there is a miniscule risk of the torrent having been removed
-        // by now, don't unwrap the result.
-        if let Some(torrent_data) = state.torrents.get(&request.info_hash){
-            match peer_status {
-                PeerStatus::Leeching => {
-                    torrent_data.num_leechers.fetch_add(1, Ordering::SeqCst);
-                },
-                PeerStatus::Seeding => {
-                    torrent_data.num_seeders.fetch_add(1, Ordering::SeqCst);
-                },
-                PeerStatus::Stopped => {}
-            };
+        match peer_status {
+            PeerStatus::Leeching => {
+                torrent_data.num_leechers.fetch_add(1, Ordering::SeqCst);
+            },
+            PeerStatus::Seeding => {
+                torrent_data.num_seeders.fetch_add(1, Ordering::SeqCst);
+            },
+            PeerStatus::Stopped => {}
+        };
 
-            match opt_removed_peer_status {
-                Some(PeerStatus::Leeching) => {
-                    torrent_data.num_leechers.fetch_sub(1, Ordering::SeqCst);
-                },
-                Some(PeerStatus::Seeding) => {
-                    torrent_data.num_seeders.fetch_sub(1, Ordering::SeqCst);
-                },
-                _ => {}
-            }
-
-            let response_peers = extract_response_peers(
-                rng,
-                &torrent_data.peers,
-                max_num_peers_to_take,
-            );
-
-            let response = Response::Announce(AnnounceResponse {
-                transaction_id: request.transaction_id,
-                announce_interval: AnnounceInterval(config.network.peer_announce_interval), // FIXME
-                leechers: NumberOfPeers(torrent_data.num_leechers.load(Ordering::SeqCst) as i32),
-                seeders: NumberOfPeers(torrent_data.num_seeders.load(Ordering::SeqCst) as i32),
-                peers: response_peers
-            });
-
-            Some((response, src))
-        } else {
-            None
+        match opt_removed_peer_status {
+            Some(PeerStatus::Leeching) => {
+                torrent_data.num_leechers.fetch_sub(1, Ordering::SeqCst);
+            },
+            Some(PeerStatus::Seeding) => {
+                torrent_data.num_seeders.fetch_sub(1, Ordering::SeqCst);
+            },
+            _ => {}
         }
+
+        let response_peers = extract_response_peers(
+            rng,
+            &torrent_data.peers,
+            max_num_peers_to_take,
+        );
+
+        let response = Response::Announce(AnnounceResponse {
+            transaction_id: request.transaction_id,
+            announce_interval: AnnounceInterval(config.network.peer_announce_interval), // FIXME
+            leechers: NumberOfPeers(torrent_data.num_leechers.load(Ordering::SeqCst) as i32),
+            seeders: NumberOfPeers(torrent_data.num_seeders.load(Ordering::SeqCst) as i32),
+            peers: response_peers
+        });
+
+        Some((response, src))
     }));
 }
 
diff --git a/aquatic_bench/src/bin/bench_handlers/main.rs b/aquatic_bench/src/bin/bench_handlers/main.rs
index dcfe4f8..8e08f84 100644
--- a/aquatic_bench/src/bin/bench_handlers/main.rs
+++ b/aquatic_bench/src/bin/bench_handlers/main.rs
@@ -4,9 +4,9 @@
 //! ```
 //! ## Average results over 50 rounds
 //! 
-//! Connect handler:   2 613 265 requests/second,   383.21 ns/request
-//! Announce handler:    293 403 requests/second,  3427.20 ns/request
-//! Scrape handler:      670 001 requests/second,  1492.61 ns/request
+//! Connect handler:   2 530 072 requests/second,   395.38 ns/request
+//! Announce handler:    309 719 requests/second,  3229.87 ns/request
+//! Scrape handler:      595 259 requests/second,  1680.01 ns/request
 //! ```
 
 use std::time::{Duration, Instant};