DHT throttling fix

include/libtorrent/aux_/session_impl.hpp

@@ -219,6 +219,7 @@ namespace libtorrent
 #endif
 				);
 			virtual ~session_impl();
+			void update_dht_announce_interval();
 			void init();
 			void start_session();
 
@@ -884,6 +885,14 @@ namespace libtorrent
 			// this announce timer is used
 			// by the DHT.
 			deadline_timer m_dht_announce_timer;
+
+			// the number of torrents there were when the
+			// update_dht_announce_interval() was last called.
+			// if the number of torrents changes significantly
+			// compared to this number, the DHT announce interval
+			// is updated again. This especially matters for
+			// small numbers.
+			int m_dht_interval_update_torrents;
 #endif
 
 			bool incoming_packet(error_code const& ec
@@ -937,6 +946,14 @@ namespace libtorrent
 			// within the DHT announce interval (which defaults to
 			// 15 minutes)
 			torrent_map::iterator m_next_dht_torrent;
+
+			// torrents that don't have any peers
+			// when added should be announced to the DHT
+			// as soon as possible. Such torrents are put
+			// in this queue and get announced the next time
+			// the timer fires, instead of the next one in
+			// the round-robin sequence.
+			std::deque<boost::weak_ptr<torrent> > m_dht_torrents;
 #endif
 
 			// this announce timer is used

src/session_impl.cpp

@@ -641,6 +641,7 @@ namespace aux {
 		, m_next_rss_update(min_time())
 #ifndef TORRENT_DISABLE_DHT
 		, m_dht_announce_timer(m_io_service)
+		, m_dht_interval_update_torrents(0)
 #endif
 		, m_external_udp_port(0)
 		, m_udp_socket(m_io_service, m_half_open)
@@ -1295,6 +1296,24 @@ namespace aux {
 		m_thread.reset(new thread(boost::bind(&session_impl::main_thread, this)));
 	}
 
+	void session_impl::update_dht_announce_interval()
+	{
+#ifndef TORRENT_DISABLE_DHT
+
+#if defined TORRENT_ASIO_DEBUGGING
+		add_outstanding_async("session_impl::on_dht_announce");
+#endif
+		m_dht_interval_update_torrents = m_torrents.size();
+		error_code ec;
+		int delay = (std::max)(m_settings.dht_announce_interval
+			/ (std::max)(int(m_torrents.size()), 1), 1);
+		m_dht_announce_timer.expires_from_now(seconds(delay), ec);
+		m_dht_announce_timer.async_wait(
+			boost::bind(&session_impl::on_dht_announce, this, _1));
+		TORRENT_ASSERT(!ec);
+#endif
+	}
+
 	void session_impl::init()
 	{
 #if defined TORRENT_LOGGING || defined TORRENT_VERBOSE_LOGGING
@@ -1323,16 +1342,7 @@ namespace aux {
 		TORRENT_ASSERT(!ec);
 
 #ifndef TORRENT_DISABLE_DHT
-
-#if defined TORRENT_ASIO_DEBUGGING
-		add_outstanding_async("session_impl::on_dht_announce");
-#endif
-		delay = (std::max)(m_settings.dht_announce_interval
-			/ (std::max)(int(m_torrents.size()), 1), 1);
-		m_dht_announce_timer.expires_from_now(seconds(delay), ec);
-		m_dht_announce_timer.async_wait(
-			boost::bind(&session_impl::on_dht_announce, this, _1));
-		TORRENT_ASSERT(!ec);
+		update_dht_announce_interval();
 #endif
 
 #if defined TORRENT_LOGGING || defined TORRENT_VERBOSE_LOGGING
@@ -3010,6 +3020,12 @@ namespace aux {
 		// only tick the following once per second
 		if (now - m_last_second_tick < seconds(1)) return;
 
+#ifndef TORRENT_DISABLE_DHT
+		if (m_dht_interval_update_torrents < 40
+			&& m_dht_interval_update_torrents != m_torrents.size())
+			update_dht_announce_interval();
+#endif
+
 		int tick_interval_ms = total_milliseconds(now - m_last_second_tick);
 		m_last_second_tick = now;
 		m_tick_residual += tick_interval_ms - 1000;
@@ -3950,11 +3966,27 @@ namespace aux {
 		m_dht_announce_timer.async_wait(
 			bind(&session_impl::on_dht_announce, this, _1));
 
+		if (!m_dht_torrents.empty())
+		{
+			boost::shared_ptr<torrent> t;
+			do
+			{
+		  		t = m_dht_torrents.front().lock();
+				m_dht_torrents.pop_front();
+			}
+			while (!t && !m_dht_torrents.empty());
+			if (t)
+			{
+				t->dht_announce();
+				return;
+			}
+		}
 		if (m_torrents.empty()) return;
 
 		if (m_next_dht_torrent == m_torrents.end())
 			m_next_dht_torrent = m_torrents.begin();
 		m_next_dht_torrent->second->dht_announce();
+		// TODO: make a list for torrents that want to be announced on the DHT
 		++m_next_dht_torrent;
 		if (m_next_dht_torrent == m_torrents.end())
 			m_next_dht_torrent = m_torrents.begin();
@@ -5365,13 +5397,6 @@ namespace aux {
 		m_dht->start(startup_state);
 
 		m_udp_socket.subscribe(m_dht.get());
-
-		// announce all torrents we have to the DHT
-		for (torrent_map::const_iterator i = m_torrents.begin()
-			, end(m_torrents.end()); i != end; ++i)
-		{
-			i->second->dht_announce();
-		}
 	}
 
 	void session_impl::stop_dht()

src/torrent.cpp

@@ -7325,6 +7325,15 @@ namespace libtorrent
 
 		m_announcing = true;
 
+#ifndef TORRENT_DISABLE_DHT
+		if (m_policy.num_peers() == 0 && m_ses.m_dht)
+		{
+			// we don't have any peers, prioritize
+			// announcing this torrent with the DHT
+			m_ses.m_dht_torrents.push_back(shared_from_this());
+		}
+#endif
+
 		if (!m_trackers.empty())
 		{
 			// tell the tracker that we're back
@@ -7348,10 +7357,6 @@ namespace libtorrent
 					|| settings().allow_i2p_mixed)))
 		{
 			if (m_ses.m_lsd) lsd_announce();
-
-#ifndef TORRENT_DISABLE_DHT
-			if (m_ses.m_dht) dht_announce();
-#endif
 		}
 	}