make tracker back-off configurable

ChangeLog

@@ -1,6 +1,7 @@
 
 0.16 release
 
+	* make tracker back-off configurable
 	* don't restart the swarm after downloading metadata from magnet links
 	* lower the default tracker retry intervals
 	* support banning web seeds sending corrupt data

bindings/python/src/session_settings.cpp

@@ -170,6 +170,8 @@ void bind_session_settings()
         .def_readwrite("enable_incoming_tcp", &session_settings::enable_incoming_tcp)
         .def_readwrite("enable_outgoing_utp", &session_settings::enable_outgoing_utp)
         .def_readwrite("enable_incoming_utp", &session_settings::enable_incoming_utp)
+        .def_readwrite("ssl_listen", &session_settings::ssl_listen)
+        .def_readwrite("tracker_backoff", &session_settings::tracker_backoff)
     ;
 
     enum_<proxy_settings::proxy_type>("proxy_type")

docs/manual.html

@@ -4299,6 +4299,8 @@ struct session_settings
         bool lock_files;
 
         int ssl_listen;
+
+        int tracker_backoff;
 };
 </pre>
 <p><tt class="docutils literal"><span class="pre">version</span></tt> is automatically set to the libtorrent version you're using
@@ -5037,6 +5039,14 @@ no SSL listen port is opened. Otherwise a socket is opened on this port. This
 setting is only taken into account when opening the regular listen port, and
 won't re-open the listen socket simply by changing this setting.</p>
 <p>It defaults to port 4433.</p>
+<p><tt class="docutils literal"><span class="pre">tracker_backoff</span></tt> determines how aggressively to back off from retrying
+failing trackers. This value determines <em>x</em> in the following formula, determining
+the number of seconds to wait until the next retry:</p>
+<blockquote>
+delay = 5 + 5 * x / 100 * fails^2</blockquote>
+<p>It defaults to 250.</p>
+<p>This setting may be useful to make libtorrent more or less aggressive in hitting
+trackers.</p>
 </div>
 </div>
 <div class="section" id="pe-settings">
@@ -6248,7 +6258,7 @@ struct peer_disconnected_alert: peer_alert
 <div class="section" id="invalid-request-alert">
 <h2>invalid_request_alert</h2>
 <p>This is a debug alert that is generated by an incoming invalid piece request.
-<tt class="docutils literal"><span class="pre">Ïp</span></tt> is the address of the peer and the <tt class="docutils literal"><span class="pre">request</span></tt> is the actual incoming
+<tt class="docutils literal"><span class="pre">ìp</span></tt> is the address of the peer and the <tt class="docutils literal"><span class="pre">request</span></tt> is the actual incoming
 request from the peer.</p>
 <pre class="literal-block">
 struct invalid_request_alert: peer_alert
@@ -7835,13 +7845,13 @@ std::string error_code_to_string(boost::system::error_code const&amp; ec)
         static const char const* swedish[] =
         {
                 &quot;inget fel&quot;,
-                &quot;en fil i torrenten kolliderar med en fil frÂn en annan torrent&quot;,
+                &quot;en fil i torrenten kolliderar med en fil från en annan torrent&quot;,
                 &quot;hash check misslyckades&quot;,
-                &quot;torrent filen ‰r inte en dictionary&quot;,
+                &quot;torrent filen är inte en dictionary&quot;,
-                &quot;'info'-nyckeln saknas eller ‰r korrupt i torrentfilen&quot;,
+                &quot;'info'-nyckeln saknas eller är korrupt i torrentfilen&quot;,
-                &quot;'info'-f‰ltet ‰r inte en dictionary&quot;,
+                &quot;'info'-fältet är inte en dictionary&quot;,
-                &quot;'piece length' f‰ltet saknas eller ‰r korrupt i torrentfilen&quot;,
+                &quot;'piece length' fältet saknas eller är korrupt i torrentfilen&quot;,
-                &quot;torrentfilen saknar namnf‰ltet&quot;,
+                &quot;torrentfilen saknar namnfältet&quot;,
                 &quot;ogiltigt namn i torrentfilen (kan vara en attack)&quot;,
                 // ... more strings here
         };

docs/manual.rst

@@ -4556,6 +4556,8 @@ session_settings
 		bool lock_files;
 
 		int ssl_listen;
+
+		int tracker_backoff;
 	};
 
 ``version`` is automatically set to the libtorrent version you're using
@@ -5442,6 +5444,17 @@ won't re-open the listen socket simply by changing this setting.
 
 It defaults to port 4433.
 
+``tracker_backoff`` determines how aggressively to back off from retrying
+failing trackers. This value determines *x* in the following formula, determining
+the number of seconds to wait until the next retry:
+
+	delay = 5 + 5 * x / 100 * fails^2
+
+It defaults to 250.
+
+This setting may be useful to make libtorrent more or less aggressive in hitting
+trackers.
+
 pe_settings
 ===========
 

include/libtorrent/session_settings.hpp

@@ -919,6 +919,14 @@ namespace libtorrent
 
 		// open an ssl listen socket for ssl torrents on this port
 		int ssl_listen;
+
+		// this is the factor X in the formula to calculate the
+		// next tracker timeout:
+		// delay = 5 + X/100 * fails^2
+		// so, it's an exponential back-off, and this factor
+		// determines how fast the back-off happens. Default
+		// is 250
+		int tracker_backoff;
 	};
 
 #ifndef TORRENT_DISABLE_DHT

include/libtorrent/torrent_info.hpp

@@ -63,6 +63,7 @@ POSSIBILITY OF SUCH DAMAGE.
 namespace libtorrent
 {
 	class peer_connection;
+	struct session_settings;
 
 	enum
 	{
@@ -144,7 +145,7 @@ namespace libtorrent
 			min_announce = min_time();
 		}
 
-		void failed(int retry_interval = 0);
+		void failed(session_settings const& sett, int retry_interval = 0);
 
 		bool will_announce(ptime now) const
 		{

src/session.cpp

@@ -1276,6 +1276,7 @@ namespace libtorrent
 		, use_disk_read_ahead(true)
 		, lock_files(false)
 		, ssl_listen(4433)
+		, tracker_backoff(250)
 	{}
 
 	session_settings::~session_settings() {}

src/session_impl.cpp

@@ -441,6 +441,8 @@ namespace aux {
 		TORRENT_SETTING(integer, read_job_every)
 		TORRENT_SETTING(boolean, use_disk_read_ahead)
 		TORRENT_SETTING(boolean, lock_files)
+		TORRENT_SETTING(integer, ssl_listen)
+		TORRENT_SETTING(integer, tracker_backoff)
 	};
 
 #undef TORRENT_SETTING

src/torrent.cpp

@@ -8454,7 +8454,7 @@ namespace libtorrent
 			announce_entry* ae = find_tracker(r);
 			if (ae)
 			{
-				ae->failed(retry_interval);
+				ae->failed(settings(), retry_interval);
 				ae->last_error = ec;
 				ae->message = msg;
 				int tracker_index = ae - &m_trackers[0];

src/torrent_info.cpp

@@ -64,6 +64,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/utf8.hpp"
 #include "libtorrent/time.hpp"
 #include "libtorrent/invariant_check.hpp"
+#include "libtorrent/session_settings.hpp"
 
 #if TORRENT_USE_I2P
 #include "libtorrent/parse_url.hpp"
@@ -470,13 +471,15 @@ namespace libtorrent
 	int announce_entry::min_announce_in() const
 	{ return total_seconds(min_announce - time_now()); }
 
-	void announce_entry::failed(int retry_interval)
+	void announce_entry::failed(session_settings const& sett, int retry_interval)
 	{
 		++fails;
 		// the exponential back-off ends up being:
 		// 7, 15, 27, 45, 95, 127, 165, ... seconds
+		// with the default tracker_backoff of 250
 		int delay = (std::min)(tracker_retry_delay_min + int(fails) * int(fails)
-			* tracker_retry_delay_min / 2, int(tracker_retry_delay_max));
+			* tracker_retry_delay_min * sett.tracker_backoff / 100
+			, int(tracker_retry_delay_max));
 		delay = (std::max)(delay, retry_interval);
 		next_announce = time_now() + seconds(delay);
 		updating = false;

test/test_primitives.cpp

@@ -400,9 +400,11 @@ int test_main()
 	// on failing announces
 	announce_entry ae("dummy");
 	int last = 0;
+	session_settings sett;
+	sett.tracker_backoff = 250;
 	for (int i = 0; i < 10; ++i)
 	{
-		ae.failed(5);
+		ae.failed(sett, 5);
 		int delay = ae.next_announce_in();
 		TEST_CHECK(delay > last);
 		last = delay;