added upload mode

ChangeLog

@@ -1,4 +1,5 @@
-	* by default, all piece priorities are set to 0 when a write fails.
+	* introduced an upload mode, which torrents are switched into when
+	  it hits a disk write error, instead of stopping the torrent.
 	  this lets libtorrent keep uploading the parts it has when it
 	  encounters a disk-full error for instance
 	* improved disk error handling and expanded use of error_code in

docs/manual.rst

@@ -38,6 +38,34 @@ For a description on how to create torrent files, see make_torrent_.
 
 .. _make_torrent: make_torrent.html
 
+things to keep in mind
+======================
+
+A common problem developers are facing is torrents stopping without explanation.
+Here is a description on which conditions libtorrent will stop your torrents,
+how to find out about it and what to do about it.
+
+Make sure to keep track of the paused state, the error state and the upload
+mode of your torrents. By default, torrents are auto-managed, which means
+libtorrent will pause them, unpause them, scrape them and take them out
+of upload-mode automatically.
+
+Whenever a torrent encounters a fatal error, it will be stopped, and the
+``session_status::error`` will describe the error that caused it. If a torrent
+is auto managed, it is scraped periodically and paused or resumed based on
+the number of downloaders per seed. This will effectively seed torrents that
+are in the greatest need of seeds.
+
+If a torrent hits a disk write error, it will be put into upload mode. This
+means it will not download anything, but only upload. The assumption is that
+the write error is caused by a full disk or write permission errors. If the
+torrent is auto-managed, it will periodically be taken out of the upload
+mode, trying to write things to the disk again. This means torrent will recover
+from certain disk errors if the problem is resolved. If the torrent is not
+auto managed, you have to call `set_upload_mode()`_ to turn
+downloading back on again.
+
+
 network primitives
 ==================
 
@@ -306,6 +334,7 @@ add_torrent()
 			void* userdata;
 			bool seed_mode;
 			bool override_resume_data;
+			bool upload_mode;
 		};
 
 		torrent_handle add_torrent(add_torrent_params const& params);
@@ -413,6 +442,11 @@ If ``override_resume_data`` is set to true, the ``paused`` and ``auto_managed``
 state of the torrent are not loaded from the resume data, but the states requested
 by this ``add_torrent_params`` will override it.
 
+If ``upload_mode`` is set to true, the torrent will be initialized in upload-mode,
+which means it will not make any piece requests. This state is typically entered
+on disk I/O errors, and if the torrent is also auto managed, it will be taken out
+of this state periodically. This mode can be used to avoid race conditions when
+adjusting priorities of pieces before allowing the torrent to start downloading.
 
 remove_torrent()
 ----------------
@@ -1841,6 +1875,7 @@ Its declaration looks like this::
 		bool is_seed() const;
 		void force_recheck() const;
 		void clear_error() const;
+		void set_upload_mode(bool m) const;
 
 		void resolve_countries(bool r);
 		bool resolve_countries() const;
@@ -2273,6 +2308,23 @@ clear_error()
 If the torrent is in an error state (i.e. ``torrent_status::error`` is non-empty), this
 will clear the error and start the torrent again.
 
+set_upload_mode()
+-----------------
+
+::
+
+		void set_upload_mode(bool m) const;
+
+Explicitly sets the upload mode of the torrent. In upload mode, the torrent will not
+request any pieces. If the torrent is auto managed, it will automatically be taken out
+of upload mode periodically (see ``session_settings::optimistic_disk_retry``). Torrents
+are automatically put in upload mode whenever they encounter a disk write error.
+
+``m`` should be true to enter upload mode, and false to leave it.
+
+To test if a torrent is in upload mode, call ``torrent_handle::status()`` and inspect
+``torrent_status::upload_mode``.
+
 resolve_countries()
 -------------------
 
@@ -2776,6 +2828,8 @@ It contains the following fields::
 		int sparse_regions;
 
 		bool seed_mode;
+
+		bool upload_mode;
 	};
 
 ``progress`` is a value in the range [0, 1], that represents the progress of the
@@ -2974,6 +3028,13 @@ a limit on the number of sparse regions in a single file there.
 started in seed mode, it will leave seed mode once all pieces have been
 checked or as soon as one piece fails the hash check.
 
+``upload_mode`` is true if the torrent is blocked from downloading. This
+typically happens when a disk write operation fails. If the torrent is
+auto-managed, it will periodically be taken out of this state, in the
+hope that the disk condition (be it disk full or permission errors) has
+been resolved. If the torrent is not auto-managed, you have to explicitly
+take it out of the upload mode by calling `set_upload_mode()`_ on the
+torrent_handle_.
 
 peer_info
 =========
@@ -3451,7 +3512,7 @@ session_settings
 		int read_cache_line_size;
 		int write_cache_line_size;
 
-		bool adjust_priority_on_disk_failure;
+		int optimistic_disk_retry;
 	};
 
 ``user_agent`` this is the client identification to the tracker.
@@ -3857,15 +3918,14 @@ When a piece in the write cache has ``write_cache_line_size`` contiguous
 blocks in it, they will be flushed. Setting this to 1 effectively
 disables the write cache.
 
-``adjust_priority_on_disk_failure`` specifies what libtorrent should do
-on disk failures. If this is set to true, instead of pausing the torrent
-and setting it to an error state when it fails to write to disk, the
-priorities of all pieces are set to 0. This effectively means the client
-can keep seeding the parts that were already downloaded, instead of
-leaving the swarm because of the error.
+``optimistic_disk_retry`` is the number of seconds from a disk write
+errors occur on a torrent until libtorrent will take it out of the
+upload mode, to test if the error condition has been fixed.
 
-If a read operation fails, it will still set an error on the torrent
-and pause it.
+libtorrent will only do this automatically for auto managed torrents.
+
+You can explicitly take a torrent out of upload only mode using
+`set_upload_mode()`_.
 
 pe_settings
 ===========

include/libtorrent/peer_connection.hpp

@@ -427,7 +427,13 @@ namespace libtorrent
 		void make_time_critical(piece_block const& block);
 
 		// adds a block to the request queue
-		void add_request(piece_block const& b, bool time_critical = false);
+		// returns true if successful, false otherwise
+		bool add_request(piece_block const& b, bool time_critical = false);
+
+		// clears the request queue and sends cancels for all messages
+		// in the download queue
+		void cancel_all_requests();
+
 		// removes a block from the request queue or download queue
 		// sends a cancel message if appropriate
 		// refills the request queue, and possibly ignoring pieces requested

include/libtorrent/session.hpp

@@ -174,6 +174,7 @@ namespace libtorrent
 			, userdata(0)
 			, seed_mode(false)
 			, override_resume_data(false)
+			, upload_mode(false)
 		{}
 
 		boost::intrusive_ptr<torrent_info> ti;
@@ -190,6 +191,7 @@ namespace libtorrent
 		void* userdata;
 		bool seed_mode;
 		bool override_resume_data;
+		bool upload_mode;
 	};
 	
 	class TORRENT_EXPORT session: public boost::noncopyable, aux::eh_initializer

include/libtorrent/session_settings.hpp

@@ -173,7 +173,7 @@ namespace libtorrent
 			, disk_cache_algorithm(largest_contiguous)
 			, read_cache_line_size(16)
 			, write_cache_line_size(32)
-			, adjust_priority_on_disk_failure(true)
+			, optimistic_disk_retry(10 * 60)
 		{}
 
 		// this is the user agent that will be sent to the tracker
@@ -600,13 +600,9 @@ namespace libtorrent
 		// is flushed immediately
 		int write_cache_line_size;
 
-		// if this is set to true, piece priorities
-		// will be automatically changed if there is
-		// an error writing to the disk, attempting
-		// to avoid hitting the error again. If there
-		// is an error reading, the torrent will be
-		// paused
-		bool adjust_priority_on_disk_failure;
+		// this is the number of seconds a disk failure
+		// occurs until libtorrent will re-try.
+		int optimistic_disk_retry;
 	};
 
 #ifndef TORRENT_DISABLE_DHT

include/libtorrent/torrent.hpp

@@ -159,6 +159,9 @@ namespace libtorrent
 		void start_announcing();
 		void stop_announcing();
 
+		void set_upload_mode(bool b);
+		bool upload_mode() const { return m_upload_mode; }
+
 		int seed_rank(session_settings const& s) const;
 
 		enum flags_t { overwrite_existing = 1 };
@@ -730,6 +733,9 @@ namespace libtorrent
 		// one of the trackers in this torrent
 		ptime m_last_scrape;
 
+		// the time when we switched to upload mode
+		ptime m_upload_mode_time;
+
 		boost::intrusive_ptr<torrent_info> m_torrent_file;
 
 		void parse_response(const entry& e, std::vector<peer_entry>& peer_list);
@@ -995,6 +1001,9 @@ namespace libtorrent
 		// is true if this torrent has been paused
 		bool m_paused:1;
 
+		// set to true when this torrent may not download anything
+		bool m_upload_mode:1;
+
 		// if this is true, libtorrent may pause and resume
 		// this torrent depending on queuing rules. Torrents
 		// started with auto_managed flag set may be added in

include/libtorrent/torrent_handle.hpp

@@ -273,6 +273,11 @@ namespace libtorrent
 
 		// is true if this torrent is (still) in seed_mode
 		bool seed_mode;
+
+		// this is set to true when the torrent is blocked
+		// from downloading, typically caused by a file
+		// write operation failing
+		bool upload_mode;
 	};
 
 	struct TORRENT_EXPORT block_info
@@ -397,6 +402,8 @@ namespace libtorrent
 		bool is_paused() const;
 		void pause() const;
 		void resume() const;
+		void set_upload_mode(bool b) const;
+
 		void force_recheck() const;
 		void save_resume_data() const;
 

src/peer_connection.cpp

@@ -2374,7 +2374,7 @@ namespace libtorrent
 		++m_queued_time_critical;
 	}
 
-	void peer_connection::add_request(piece_block const& block, bool time_critical)
+	bool peer_connection::add_request(piece_block const& block, bool time_critical)
 	{
 //		INVARIANT_CHECK;
 
@@ -2393,6 +2393,8 @@ namespace libtorrent
 		TORRENT_ASSERT(std::find(m_request_queue.begin(), m_request_queue.end()
 			, block) == m_request_queue.end());
 
+		if (t->upload_mode()) return false;
+
 		piece_picker::piece_state_t state;
 		peer_speed_t speed = peer_speed();
 		char const* speedmsg = 0;
@@ -2413,7 +2415,7 @@ namespace libtorrent
 		}
 
 		if (!t->picker().mark_as_downloading(block, peer_info_struct(), state))
-			return;
+			return false;
 
 		if (t->alerts().should_post<block_downloading_alert>())
 		{
@@ -2431,6 +2433,53 @@ namespace libtorrent
 		{
 			m_request_queue.push_back(block);
 		}
+		return true;
+	}
+
+	void peer_connection::cancel_all_requests()
+	{
+		INVARIANT_CHECK;
+
+		boost::shared_ptr<torrent> t = m_torrent.lock();
+		// this peer might be disconnecting
+		if (!t) return;
+
+		TORRENT_ASSERT(t->valid_metadata());
+
+#ifdef TORRENT_VERBOSE_LOGGING
+		(*m_logger) << time_now_string() << " *** CANCEL ALL REQUESTS\n";
+#endif
+
+		while (!m_request_queue.empty())
+		{
+			t->picker().abort_download(m_request_queue.back());
+			m_request_queue.pop_back();
+		}
+
+		for (std::vector<pending_block>::iterator i = m_download_queue.begin()
+			, end(m_download_queue.end()); i != end; ++i)
+		{
+			piece_block b = i->block;
+
+			int block_offset = b.block_index * t->block_size();
+			int block_size
+				= (std::min)(t->torrent_file().piece_size(b.piece_index)-block_offset,
+					t->block_size());
+			TORRENT_ASSERT(block_size > 0);
+			TORRENT_ASSERT(block_size <= t->block_size());
+
+			peer_request r;
+			r.piece = b.piece_index;
+			r.start = block_offset;
+			r.length = block_size;
+
+#ifdef TORRENT_VERBOSE_LOGGING
+			(*m_logger) << time_now_string()
+				<< " ==> CANCEL  [ piece: " << b.piece_index << " | s: "
+				<< block_offset << " | l: " << block_size << " | " << b.block_index << " ]\n";
+#endif
+			write_cancel(r);
+		}
 	}
 
 	void peer_connection::cancel_request(piece_block const& block)
@@ -2588,7 +2637,8 @@ namespace libtorrent
 		boost::shared_ptr<torrent> t = m_torrent.lock();
 		TORRENT_ASSERT(t);
 
-		if ((int)m_download_queue.size() >= m_desired_queue_size) return;
+		if ((int)m_download_queue.size() >= m_desired_queue_size
+			|| t->upload_mode()) return;
 
 		bool empty_download_queue = m_download_queue.empty();
 

src/policy.cpp

@@ -193,6 +193,7 @@ namespace libtorrent
 	{
 		if (t.is_seed()) return;
 		if (c.no_download()) return;
+		if (t.upload_mode()) return;
 
 		TORRENT_ASSERT(t.valid_metadata());
 		TORRENT_ASSERT(c.peer_info_struct() != 0 || !dynamic_cast<bt_peer_connection*>(&c));
@@ -313,7 +314,7 @@ namespace libtorrent
 			// ok, we found a piece that's not being downloaded
 			// by somebody else. request it from this peer
 			// and return
-			c.add_request(*i);
+			if (!c.add_request(*i)) continue;
 			TORRENT_ASSERT(p.num_peers(*i) == 1);
 			TORRENT_ASSERT(p.is_requested(*i));
 			num_requests--;

src/torrent.cpp

@@ -144,6 +144,7 @@ namespace libtorrent
 		, m_total_downloaded(0)
 		, m_started(time_now())
 		, m_last_scrape(min_time())
+		, m_upload_mode_time(time_now())
 		, m_torrent_file(p.ti ? p.ti : new torrent_info(p.info_hash))
 		, m_storage(0)
 		, m_host_resolver(ses.m_io_service)
@@ -180,6 +181,7 @@ namespace libtorrent
 		, m_time_scaler(0)
 		, m_abort(false)
 		, m_paused(p.paused)
+		, m_upload_mode(p.upload_mode)
 		, m_auto_managed(p.auto_managed)
 #ifndef TORRENT_DISABLE_RESOLVE_COUNTRIES
 		, m_resolving_country(false)
@@ -341,6 +343,36 @@ namespace libtorrent
 		}
 	}
 
+	void torrent::set_upload_mode(bool b)
+	{
+		if (b == m_upload_mode) return;
+
+		m_upload_mode = b;
+
+		if (m_upload_mode)
+		{
+			// clear request queues of all peers
+			for (std::set<peer_connection*>::iterator i = m_connections.begin()
+				, end(m_connections.end()); i != end; ++i)
+			{
+				peer_connection* p = (*i);
+				p->cancel_all_requests();
+			}
+			// this is used to try leaving upload only mode periodically
+			m_upload_mode_time = time_now();
+		}
+		else
+		{
+			// send_block_requests on all peers
+			for (std::set<peer_connection*>::iterator i = m_connections.begin()
+				, end(m_connections.end()); i != end; ++i)
+			{
+				peer_connection* p = (*i);
+				p->send_block_requests();
+			}
+		}
+	}
+
 	void torrent::handle_disk_error(disk_io_job const& j, peer_connection* c)
 	{
 		if (!j.error) return;
@@ -389,20 +421,8 @@ namespace libtorrent
 			// and the filesystem doesn't support sparse files, only zero the priorities
 			// of the pieces that are at the tails of all files, leaving everything
 			// up to the highest written piece in each file
-			if (m_ses.settings().adjust_priority_on_disk_failure
-				&& has_picker())
-			{
-				bool filter_updated = false;
-				bool was_finished = is_finished();
-				const int num_pieces = m_torrent_file->num_pieces();
-				for (int i = 0; i < num_pieces; ++i)
-				{
-					filter_updated |= m_picker->set_piece_priority(i, 0);
-					TORRENT_ASSERT(num_have() >= m_picker->num_have_filtered());
-				}
-				if (filter_updated) update_peer_interest(was_finished);
-				return;
-			}
+			set_upload_mode(true);
+			return;
 		}
 
 		// put the torrent in an error-state
@@ -4897,6 +4917,8 @@ namespace libtorrent
 	{
 		INVARIANT_CHECK;
 
+		ptime now = time_now();
+
 #ifndef TORRENT_DISABLE_EXTENSIONS
 		for (extension_list_t::iterator i = m_extensions.begin()
 			, end(m_extensions.end()); i != end; ++i)
@@ -4932,6 +4954,15 @@ namespace libtorrent
 			m_policy.pulse();
 		}
 
+		// if we're in upload only mode and we're auto-managed
+		// leave upload mode every 10 minutes hoping that the error
+		// condition has been fixed
+		if (m_upload_mode && m_auto_managed && now - m_upload_mode_time
+			> seconds(m_settings.optimistic_disk_retry))
+		{
+			set_upload_mode(false);
+		}
+
 		if (is_paused())
 		{
 			// let the stats fade out to 0
@@ -4965,8 +4996,6 @@ namespace libtorrent
 		if (is_seed()) m_seeding_time += since_last_tick;
 		m_active_time += since_last_tick;
 
-		ptime now = time_now();
-
 		// ---- TIME CRITICAL PIECES ----
 
 		if (!m_time_critical_pieces.empty())
@@ -5437,6 +5466,7 @@ namespace libtorrent
 		{
 			st.last_scrape = total_seconds(now - m_last_scrape);
 		}
+		st.upload_mode = m_upload_mode;
 		st.up_bandwidth_queue = 0;
 		st.down_bandwidth_queue = 0;
 

src/torrent_handle.cpp

@@ -290,6 +290,12 @@ namespace libtorrent
 		TORRENT_FORWARD(pause());
 	}
 
+	void torrent_handle::set_upload_mode(bool b) const
+	{
+		INVARIANT_CHECK;
+		TORRENT_FORWARD(set_upload_mode(b));
+	}
+
 	void torrent_handle::save_resume_data() const
 	{
 		INVARIANT_CHECK;

test/test_transfer.cpp

@@ -271,24 +271,11 @@ void test_transfer(bool test_disk_full = false)
 			std::cerr << "moving storage" << std::endl;
 		}
 
-		if (test_disk_full && tor2.is_finished())
+		if (test_disk_full && st2.upload_mode)
 		{
 			test_disk_full = false;
-			std::vector<int> priorities2 = tor2.piece_priorities();
-			std::cerr << "piece priorities: ";
-			for (std::vector<int>::iterator i = priorities2.begin()
-				, end(priorities2.end()); i != end; ++i)
-			{
-				TEST_CHECK(*i == 0);
-				std::cerr << *i << ", ";
-			}
-			std::cerr << std::endl;
-
 			((test_storage*)tor2.get_storage_impl())->m_limit = 16 * 1024 * 1024;
-			tor2.prioritize_pieces(priorities);
-			std::cerr << "setting priorities: ";
-			std::copy(priorities.begin(), priorities.end(), std::ostream_iterator<int>(std::cerr, ", "));
-			std::cerr << std::endl;
+			tor2.set_upload_mode(false);
 			continue;
 		}