deliver notification of alerts being dropped via alerts_dropped_alert

ChangeLog

@@ -1,10 +1,10 @@
+	* deliver notification of alerts being dropped via alerts_dropped_alert
 	* deprecated alert::progress_notification alert category, split into
 	  finer grained categories
 	* update plugin interface functions for improved type-safety
 	* implemented support magnet URI extension, select specific file indices
 	  for download, BEP53
 	* make tracker keys multi-homed. remove set_key() function on session.
-	* add API to query whether alerts have been dropped or not
 	* add flags()/set_flags()/unset_flags() to torrent_handle, deprecate individual functions
 	* added alert for block being sent to the send buffer
 	* drop support for windows compilers without std::wstring

include/libtorrent/alert_manager.hpp

@@ -54,10 +54,6 @@ namespace libtorrent {
 	struct plugin;
 #endif
 
-	// this bitset is used to indicate which alert types have been dropped since
-	// last queried.
-	using dropped_alerts_t = std::bitset<num_alert_types>;
-
 	class TORRENT_EXTRA_EXPORT alert_manager
 	{
 	public:
@@ -69,8 +65,6 @@ namespace libtorrent {
 
 		~alert_manager();
 
-		dropped_alerts_t dropped_alerts();
-
 		template <class T, typename... Args>
 		void emplace_alert(Args&&... args) try
 		{
@@ -145,7 +139,7 @@ namespace libtorrent {
 		// an alert (because the queue is full or of some other error) we set the
 		// corresponding bit in this mask, to communicate to the client that it
 		// may have missed an update.
-		dropped_alerts_t m_dropped;
+		std::bitset<num_alert_types> m_dropped;
 
 		// this function (if set) is called whenever the number of alerts in
 		// the alert queue goes from 0 to 1. The client is expected to wake up

include/libtorrent/alert_types.hpp

@@ -59,6 +59,8 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <boost/shared_array.hpp>
 #include "libtorrent/aux_/disable_warnings_pop.hpp"
 
+#include <bitset>
+
 #if TORRENT_ABI_VERSION == 1
 #define PROGRESS_NOTIFICATION | alert::progress_notification
 #else
@@ -72,8 +74,14 @@ namespace libtorrent {
 	TORRENT_DEPRECATED_EXPORT char const* operation_name(int op);
 #endif
 
+	// internal
+	TORRENT_EXTRA_EXPORT char const* alert_name(int alert_type);
+
 	// user defined alerts should use IDs greater than this
-	static const int user_alert_id = 10000;
+	constexpr int user_alert_id = 10000;
+
+	// this constant represents "max_alert_index" + 1
+	constexpr int num_alert_types = 96;
 
 	enum alert_priority
 	{
@@ -190,7 +198,7 @@ TORRENT_VERSION_NAMESPACE_2
 	static const int alert_type = seq; \
 	virtual int type() const noexcept override { return alert_type; } \
 	virtual alert_category_t category() const noexcept override { return static_category; } \
-	virtual char const* what() const noexcept override { return #name; }
+	virtual char const* what() const noexcept override { return alert_name(alert_type); }
 
 #define TORRENT_DEFINE_ALERT(name, seq) \
 	TORRENT_DEFINE_ALERT_IMPL(name, seq, alert_priority_normal)
@@ -1848,7 +1856,7 @@ TORRENT_VERSION_NAMESPACE_2
 	};
 
 	// This alert is posted whenever a tracker responds with a ``trackerid``.
-	// The tracker ID is like a cookie. The libtorrent will store the tracker ID
+	// The tracker ID is like a cookie. libtorrent will store the tracker ID
 	// for this tracker and repeat it in subsequent announces.
 	struct TORRENT_EXPORT trackerid_alert final : tracker_alert
 	{
@@ -2839,6 +2847,25 @@ TORRENT_VERSION_NAMESPACE_2
 		piece_index_t const piece_index;
 	};
 
+	// this alert is posted to indicate to the client that some alerts were
+	// dropped. Dropped meaning that the alert failed to be delivered to the
+	// client. The most common cause of such failure is that the internal alert
+	// queue grew too big (controlled by alert_queue_size).
+	struct TORRENT_EXPORT alerts_dropped_alert final : alert
+	{
+		explicit alerts_dropped_alert(aux::stack_allocator& alloc
+			, std::bitset<num_alert_types> const&);
+		TORRENT_DEFINE_ALERT_PRIO(alerts_dropped_alert, 95, alert_priority_critical + 1)
+
+		static constexpr alert_category_t static_category = alert::error_notification;
+		std::string message() const override;
+
+		// a bitmask indicating which alerts were dropped. Each bit represents the
+		// alert type ID, where bit 0 represents whether any alert of type 0 has
+		// been dropped, and so on.
+		std::bitset<num_alert_types> dropped_alerts;
+	};
+
 TORRENT_VERSION_NAMESPACE_2_END
 
 #undef TORRENT_DEFINE_ALERT_IMPL
@@ -2846,7 +2873,6 @@ TORRENT_VERSION_NAMESPACE_2_END
 #undef TORRENT_DEFINE_ALERT_PRIO
 #undef PROGRESS_NOTIFICATION
 
-	constexpr int num_alert_types = 95; // this constant represents "max_alert_index" + 1
 }
 
 #endif

include/libtorrent/session_handle.hpp

@@ -46,7 +46,6 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/io_service.hpp"
 #include "libtorrent/session_types.hpp"
 #include "libtorrent/portmap.hpp" // for portmap_protocol
-#include "libtorrent/alert_manager.hpp" // for dropped_alerts_t
 
 #include "libtorrent/kademlia/dht_storage.hpp"
 #include "libtorrent/kademlia/dht_settings.hpp"
@@ -933,21 +932,12 @@ namespace libtorrent {
 		// callback should not block. It should not perform any expensive work.
 		// It really should just notify the main application thread.
 		//
-		// The ``dropped_alerts()`` function returns a ``std::bitfield``
-		// representing which types of alerts have been dropped. Dropped meaning
-		// that the alert failed to be delivered to the client. The most common
-		// cause of such failure is that the internal alert queue grew too big
-		// (controlled by alert_queue_size). This call also clears the internal
-		// bitfield, so the bitfield starts recording dropped alerts from this
-		// point forward only.
-		//
 		// The type of an alert is returned by the polymorphic function
 		// ``alert::type()`` but can also be queries from a concrete type via
 		// ``T::alert_type``, as a static constant.
 		void pop_alerts(std::vector<alert*>* alerts);
 		alert* wait_for_alert(time_duration max_wait);
 		void set_alert_notify(std::function<void()> const& fun);
-		dropped_alerts_t dropped_alerts();
 
 #if TORRENT_ABI_VERSION == 1
 #include "libtorrent/aux_/disable_warnings_push.hpp"

src/alert.cpp

@@ -2540,6 +2540,83 @@ namespace {
 		return ret;
 	}
 
+	alerts_dropped_alert::alerts_dropped_alert(aux::stack_allocator&
+		, std::bitset<num_alert_types> const& dropped)
+		: dropped_alerts(dropped)
+	{}
+
+	char const* alert_name(int const alert_type)
+	{
+		static std::array<char const*, num_alert_types> const names = {{
+#if TORRENT_ABI_VERSION == 1
+		"torrent", "peer", "tracker", "torrent_added",
+#else
+		"", "", "", "",
+#endif
+		"torrent_removed", "read_piece", "file_completed",
+		"file_renamed", "file_rename_failed", "performance",
+		"state_changed", "tracker_error", "tracker_warning",
+		"scrape_reply", "scrape_failed", "tracker_reply",
+		"dht_reply", "tracker_announce", "hash_failed",
+		"peer_ban", "peer_unsnubbed", "peer_snubbed",
+		"peer_error", "peer_connect", "peer_disconnected",
+		"invalid_request", "torrent_finished", "piece_finished",
+		"request_dropped", "block_timeout", "block_finished",
+		"block_downloading", "unwanted_block", "storage_moved",
+		"storage_moved_failed", "torrent_deleted",
+		"torrent_delete_failed", "save_resume_data",
+		"save_resume_data_failed", "torrent_paused",
+		"torrent_resumed", "torrent_checked", "url_seed",
+		"file_error", "metadata_failed", "metadata_received",
+		"udp_error", "external_ip", "listen_failed",
+		"listen_succeeded", "portmap_error", "portmap",
+		"portmap_log", "fastresume_rejected", "peer_blocked",
+		"dht_announce", "dht_get_peers", "stats",
+		"cache_flushed", "anonymous_mode", "lsd_peer",
+		"trackerid", "dht_bootstrap", "", "torrent_error",
+		"torrent_need_cert", "incoming_connection",
+		"add_torrent", "state_update",
+#if TORRENT_ABI_VERSION == 1
+		"mmap_cache",
+#else
+		"",
+#endif
+		"session_stats",
+#if TORRENT_ABI_VERSION == 1
+		"torrent_update",
+#else
+		"",
+#endif
+		"", "dht_error", "dht_immutable_item", "dht_mutable_item",
+		"dht_put", "i2p", "dht_outgoing_get_peers", "log",
+		"torrent_log", "peer_log", "lsd_error",
+		"dht_stats", "incoming_request", "dht_log",
+		"dht_pkt", "dht_get_peers_reply", "dht_direct_response",
+		"picker_log", "session_error", "dht_live_nodes",
+		"session_stats_header", "dht_sample_infohashes",
+		"block_uploaded", "alerts_dropped"
+		}};
+
+		TORRENT_ASSERT(alert_type >= 0);
+		TORRENT_ASSERT(alert_type < num_alert_types);
+		return names[std::size_t(alert_type)];
+	}
+
+	std::string alerts_dropped_alert::message() const
+	{
+		std::string ret = "dropped alerts: ";
+
+		TORRENT_ASSERT(int(dropped_alerts.size()) == num_alert_types);
+		for (int idx = 0; idx < num_alert_types; ++idx)
+		{
+			if (!dropped_alerts.test(std::size_t(idx))) continue;
+			ret += alert_name(idx);
+			ret += ' ';
+		}
+
+		return ret;
+	}
+
 	// this will no longer be necessary in C++17
 	constexpr alert_category_t torrent_removed_alert::static_category;
 	constexpr alert_category_t read_piece_alert::static_category;
@@ -2628,6 +2705,7 @@ namespace {
 	constexpr alert_category_t session_stats_header_alert::static_category;
 	constexpr alert_category_t dht_sample_infohashes_alert::static_category;
 	constexpr alert_category_t block_uploaded_alert::static_category;
+	constexpr alert_category_t alerts_dropped_alert::static_category;
 #if TORRENT_ABI_VERSION == 1
 	constexpr alert_category_t mmap_cache_alert::static_category;
 	constexpr alert_category_t torrent_added_alert::static_category;

src/alert_manager.cpp

@@ -108,6 +108,11 @@ namespace libtorrent {
 
 		if (m_alerts[m_generation].empty()) return;
 
+		if (m_dropped.any()) {
+			emplace_alert<alerts_dropped_alert>(m_dropped);
+			m_dropped.reset();
+		}
+
 		m_alerts[m_generation].get_pointers(alerts);
 
 		// swap buffers
@@ -130,12 +135,4 @@ namespace libtorrent {
 		std::swap(m_queue_size_limit, queue_size_limit_);
 		return queue_size_limit_;
 	}
-
-	dropped_alerts_t alert_manager::dropped_alerts()
-	{
-		std::unique_lock<std::recursive_mutex> lock(m_mutex);
-		dropped_alerts_t const ret = m_dropped;
-		m_dropped.reset();
-		return ret;
-	}
 }

src/session_handle.cpp

@@ -1144,13 +1144,6 @@ namespace {
 		s->alerts().set_notify_function(fun);
 	}
 
-	dropped_alerts_t session_handle::dropped_alerts()
-	{
-		std::shared_ptr<session_impl> s = m_impl.lock();
-		if (!s) aux::throw_ex<system_error>(errors::invalid_session_handle);
-		return s->alerts().dropped_alerts();
-	}
-
 #if TORRENT_ABI_VERSION == 1
 	void session_handle::set_severity_level(alert::severity_t s)
 	{

src/storage_utils.cpp

@@ -38,6 +38,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/session.hpp" // for session::delete_files
 #include "libtorrent/stat_cache.hpp"
 #include "libtorrent/add_torrent_params.hpp"
+#include "libtorrent/torrent_status.hpp"
 
 #include <set>
 

test/test_alert_manager.cpp

@@ -60,7 +60,8 @@ TORRENT_TEST(limit)
 	mgr.get_all(alerts);
 
 	// even though we posted 600, the limit was 500
-	TEST_EQUAL(alerts.size(), 500);
+	// +1 for the alerts_dropped_alert
+	TEST_EQUAL(alerts.size(), 501);
 
 	TEST_EQUAL(mgr.pending(), false);
 
@@ -75,7 +76,8 @@ TORRENT_TEST(limit)
 	mgr.get_all(alerts);
 
 	// even though we posted 600, the limit was 200
-	TEST_EQUAL(alerts.size(), 200);
+	// +1 for the alerts_dropped_alert
+	TEST_EQUAL(alerts.size(), 201);
 }
 
 TORRENT_TEST(priority_limit)
@@ -97,7 +99,8 @@ TORRENT_TEST(priority_limit)
 
 	// even though we posted 500, the limit was 100 for half of them and
 	// 100 + 200 for the other half, meaning we should have 300 alerts now
-	TEST_EQUAL(alerts.size(), 300);
+	// +1 for the alerts_dropped_alert
+	TEST_EQUAL(alerts.size(), 301);
 }
 
 namespace {
@@ -260,22 +263,33 @@ TORRENT_TEST(dropped_alerts)
 	alert_manager mgr(1, alert::all_categories);
 
 	// nothing has dropped yet
-	TEST_CHECK(mgr.dropped_alerts().none());
 	mgr.emplace_alert<torrent_finished_alert>(torrent_handle());
 	// still nothing, there's space for one alert
-	TEST_CHECK(mgr.dropped_alerts().none());
 	mgr.emplace_alert<torrent_finished_alert>(torrent_handle());
 	// still nothing, there's space for one alert
-	TEST_CHECK(mgr.dropped_alerts().none());
 	mgr.emplace_alert<torrent_finished_alert>(torrent_handle());
 	// that last alert got dropped though, since it would have brought the queue
 	// size to 3
-	auto const d = mgr.dropped_alerts();
+	std::vector<alert*> alerts;
+	mgr.get_all(alerts);
+	auto const d = alert_cast<alerts_dropped_alert>(alerts.back())->dropped_alerts;
 	TEST_EQUAL(d.count(), 1);
 	TEST_CHECK(d.test(torrent_finished_alert::alert_type));
+}
 
-	// it should have been cleared now though
-	TEST_CHECK(mgr.dropped_alerts().none());
+TORRENT_TEST(alerts_dropped_alert)
+{
+	alert_manager mgr(1, alert::all_categories);
+
+	mgr.emplace_alert<torrent_finished_alert>(torrent_handle());
+	mgr.emplace_alert<torrent_finished_alert>(torrent_handle());
+	mgr.emplace_alert<torrent_finished_alert>(torrent_handle());
+	// that last alert got dropped though, since it would have brought the queue
+	// size to 3
+	std::vector<alert*> alerts;
+	mgr.get_all(alerts);
+
+	TEST_EQUAL(alerts.back()->message(), "dropped alerts: torrent_finished ");
 }
 
 #ifndef TORRENT_DISABLE_EXTENSIONS

test/test_alert_types.cpp

@@ -58,6 +58,7 @@ TORRENT_TEST(alerts_types)
 	TEST_EQUAL(name::alert_type, seq); \
 	TEST_EQUAL(name::static_category, cat); \
 	TEST_EQUAL(count_alert_types, seq); \
+	TEST_EQUAL(std::string(alert_name(name::alert_type)) + "_alert", #name); \
 	count_alert_types++;
 
 #if TORRENT_ABI_VERSION == 1
@@ -171,10 +172,11 @@ TORRENT_TEST(alerts_types)
 	TEST_ALERT_TYPE(session_stats_header_alert, 92, 0, alert::stats_notification);
 	TEST_ALERT_TYPE(dht_sample_infohashes_alert, 93, 0, alert::dht_operation_notification);
 	TEST_ALERT_TYPE(block_uploaded_alert, 94, 0, PROGRESS_NOTIFICATION alert::upload_notification);
+	TEST_ALERT_TYPE(alerts_dropped_alert, 95, 3, alert::error_notification);
 
 #undef TEST_ALERT_TYPE
 
-	TEST_EQUAL(num_alert_types, 95);
+	TEST_EQUAL(num_alert_types, 96);
 	TEST_EQUAL(num_alert_types, count_alert_types);
 }