try to reduce the level of useless dht tracker requests by not announcing empty torrents we do not follow.

libtorrent/include/libtorrent/torrent.hpp

@@ -513,6 +513,7 @@ namespace libtorrent
 		}
 		
 		void super_seeding(bool on);
+		void set_following(bool on);
 		int get_piece_to_super_seed(bitfield const&);
 
 		// returns true if we have downloaded the given piece
@@ -1220,6 +1221,9 @@ namespace libtorrent
 		// torrent.
 		bool m_super_seeding:1;
 		
+		// if this is true, we're currently following this user
+		bool m_following:1;
+
 		// this is set when we don't want to load seed_mode,
 		// paused or auto_managed from the resume data
 		bool m_override_resume_data:1;

libtorrent/include/libtorrent/torrent_handle.hpp

@@ -412,6 +412,7 @@ namespace libtorrent
 #endif
 
 		void super_seeding(bool on) const;
+		void set_following(bool on) const;
 
 		sha1_hash info_hash() const;
 

libtorrent/src/torrent.cpp

@@ -387,6 +387,7 @@ namespace libtorrent
 		, m_got_tracker_response(false)
 		, m_connections_initialized(false)
 		, m_super_seeding(false)
+		, m_following(false)
 		, m_override_resume_data(p.flags & add_torrent_params::flag_override_resume_data)
 #ifndef TORRENT_DISABLE_RESOLVE_COUNTRIES
 		, m_resolving_country(false)
@@ -827,6 +828,10 @@ namespace libtorrent
 		// because the info-hash is just the URL hash
 		if (!m_torrent_file->is_valid() && !m_url.empty()) return false;
 
+		// try to reduce the level of useless dht tracker requests by not
+		// announcing empty torrents we do not follow.
+		if (!m_following && last_have() == -1 ) return false;
+
 		// don't announce private torrents
 		if (m_torrent_file->is_valid() && m_torrent_file->priv()) return false;
 		if (m_trackers.empty()) return true;
@@ -3509,6 +3514,11 @@ namespace libtorrent
 		}
 	}
 
+	void torrent::set_following(bool on)
+	{
+		m_following = on;
+	}
+
 	int torrent::get_piece_to_super_seed(bitfield const& bits)
 	{
 		// return a piece with low availability that is not in

libtorrent/src/torrent_handle.cpp

@@ -975,6 +975,12 @@ namespace libtorrent
 		TORRENT_ASYNC_CALL1(super_seeding, on);
 	}
 
+	void torrent_handle::set_following(bool on) const
+	{
+		INVARIANT_CHECK;
+		TORRENT_ASYNC_CALL1(set_following, on);
+	}
+
 	void torrent_handle::resolve_countries(bool r)
 	{
 		INVARIANT_CHECK;

src/twister.cpp

@@ -72,7 +72,7 @@ sha1_hash dhtTargetHash(std::string const &username, std::string const &resource
     return hasher(buf.data(), buf.size()).final();
 }
 
-torrent_handle startTorrentUser(std::string const &username)
+torrent_handle startTorrentUser(std::string const &username, bool following)
 {
     bool userInTxDb = usernameExists(username); // keep this outside cs_twister to avoid deadlock
     if( !userInTxDb )
@@ -96,6 +96,8 @@ torrent_handle startTorrentUser(std::string const &username)
         m_userTorrent[username] = ses->add_torrent(tparams);
         m_userTorrent[username].force_dht_announce();
     }
+    if( following ) 
+        m_userTorrent[username].set_following(true);
     return m_userTorrent[username];
 }
 
@@ -298,7 +300,7 @@ void ThreadWaitExtIP()
     }
     // now restart the user torrents
     BOOST_FOREACH(string username, torrentsToStart) {
-        startTorrentUser(username);
+        startTorrentUser(username, true);
     }
 }
 
@@ -601,7 +603,7 @@ void ThreadSessionAlerts()
                         neighborCheck.count(ih) ) {
                         // Do something!
                         if( dd->m_resource == "tracker" ) {
-                            startTorrentUser(dd->m_username);
+                            startTorrentUser(dd->m_username, false);
                         } else {
                             printf("Neighbor of special resource - do something!\n");
                         }
@@ -1285,7 +1287,7 @@ Value newpostmsg(const Array& params, bool fHelp)
     if( !acceptSignedPost(buf.data(),buf.size(),strUsername,k,errmsg,NULL) )
         throw JSONRPCError(RPC_INVALID_PARAMS,errmsg);
 
-    torrent_handle h = startTorrentUser(strUsername);
+    torrent_handle h = startTorrentUser(strUsername, true);
     if( h.is_valid() ) {
         // if member of torrent post it directly
         h.add_piece(k,buf.data(),buf.size());
@@ -1371,7 +1373,7 @@ Value newdirectmsg(const Array& params, bool fHelp)
         m_users[strFrom].m_directmsg[strTo].push_back(stoDM);
     }
 
-    torrent_handle h = startTorrentUser(strFrom);
+    torrent_handle h = startTorrentUser(strFrom, true);
     h.add_piece(k,buf.data(),buf.size());
 
     hexcapePost(v);
@@ -1413,7 +1415,7 @@ Value newrtmsg(const Array& params, bool fHelp)
     if( !acceptSignedPost(buf.data(),buf.size(),strUsername,k,errmsg,NULL) )
         throw JSONRPCError(RPC_INVALID_PARAMS,errmsg);
 
-    torrent_handle h = startTorrentUser(strUsername);
+    torrent_handle h = startTorrentUser(strUsername, true);
     if( h.is_valid() ) {
         // if member of torrent post it directly
         h.add_piece(k,buf.data(),buf.size());
@@ -1618,7 +1620,7 @@ Value follow(const Array& params, bool fHelp)
 
     for( unsigned int u = 0; u < users.size(); u++ ) {
         string username = users[u].get_str();
-        torrent_handle h = startTorrentUser(username);
+        torrent_handle h = startTorrentUser(username, true);
 
         if( h.is_valid() ) {
             LOCK(cs_twister);