Flush session saves before stopped announces and report shutdown save errors

Persist resume data on the first shutdown pass; consume futures with one error policy.

src/control.cc

@@ -10,6 +10,7 @@
 #include <torrent/utils/directory_events.h>
 
 #include "core/dht_manager.h"
+#include "core/download_list.h"
 #include "core/http_queue.h"
 #include "core/manager.h"
 #include "core/view_manager.h"
@@ -137,6 +138,14 @@ Control::handle_shutdown() {
   if (scgi_thread::thread()->is_active())
     scgi_thread::thread()->stop_thread_wait();
 
+  if (!m_shutdown_session_saved) {
+    // Flush the latest state before stopped announces can consume the timeout.
+    // A shutdown hook may already have queued these resume builds.
+    m_core->download_list()->session_save();
+    session_thread::manager()->flush_shutdown_saves();
+    m_shutdown_session_saved = true;
+  }
+
   if (!m_shutdown_quick) {
     torrent::runtime::network_manager()->listen_close();
     torrent::runtime::shutdown();

src/control.h

@@ -114,6 +114,7 @@ private:
 
   align_cacheline
 
+  bool                m_shutdown_session_saved{};
   std::atomic<bool>   m_shutdown_received{};
   std::atomic<bool>   m_shutdown_quick{};
 };

src/session/session_manager.cc

@@ -405,42 +405,64 @@ SessionManager::process_finished_saves() {
   if (!m_active)
     throw torrent::internal_error("SessionManager::process_finished_saves() called while not active.");
 
-  for (auto& request : m_finished_saves) {
-    try {
-      request.first.get();
-
-    } catch (torrent::storage_error& e) {
-      LT_LOG("error saving download : storage error :download:%p path:%s : %s", request.second.download, request.second.path.c_str(), e.what());
-
-      if (m_last_storage_error_message + std::chrono::minutes(5) > torrent::this_thread::cached_time()) {
-        m_ignored_storage_error_count++;
-        continue;
-      }
-
-      lt_log_print(torrent::LOG_ERRORS, "Storage errors saving session data for download: ignored:%u : %s", m_ignored_storage_error_count, e.what());
-
-      m_last_storage_error_message = torrent::this_thread::cached_time();
-      m_ignored_storage_error_count = 0;
-
-      continue;
-
-    } catch (torrent::internal_error& e) {
-      LT_LOG("error saving download : internal error : download:%p path:%s : %s", request.second.download, request.second.path.c_str(), e.what());
-      throw;
-
-    } catch (...) {
-      LT_LOG("error saving download : unknown error : download:%p path:%s", request.second.download, request.second.path.c_str());
-      throw;
-    }
-
-    LT_LOG("finished saving download : download:%p path:%s", request.second.download, request.second.path.c_str());
-  }
+  for (auto& request : m_finished_saves)
+    consume_finished_save_unsafe(request);
 
   m_finished_saves.clear();
 
   callback_save_request();
 }
 
+// Storage errors share a five-minute log limit and count what they suppress.
+// Returns true when this one was suppressed. Callers hold m_mutex.
+bool
+SessionManager::report_storage_error_unsafe(const std::string& what) {
+  if (m_last_storage_error_message + std::chrono::minutes(5) > torrent::this_thread::cached_time()) {
+    m_ignored_storage_error_count++;
+    return true;
+  }
+
+  lt_log_print(torrent::LOG_ERRORS, "Storage errors saving session data for download: ignored:%u : %s", m_ignored_storage_error_count, what.c_str());
+
+  m_last_storage_error_message = torrent::this_thread::cached_time();
+  m_ignored_storage_error_count = 0;
+  return false;
+}
+
+// The one policy for a finished save, on the session thread and in shutdown
+// flushes: storage errors go to report_storage_error_unsafe(), internal and
+// unknown errors propagate. Callers hold m_mutex. Returns true when a storage
+// error was suppressed.
+bool
+SessionManager::consume_finished_save_unsafe(ProcessingSave& request) {
+  try {
+    request.first.get();
+
+  } catch (torrent::storage_error& e) {
+    LT_LOG("error saving download : storage error :download:%p path:%s : %s", request.second.download, request.second.path.c_str(), e.what());
+    return report_storage_error_unsafe(e.what());
+
+  } catch (torrent::internal_error& e) {
+    LT_LOG("error saving download : internal error : download:%p path:%s : %s", request.second.download, request.second.path.c_str(), e.what());
+    throw;
+
+  } catch (...) {
+    LT_LOG("error saving download : unknown error : download:%p path:%s", request.second.download, request.second.path.c_str());
+    throw;
+  }
+
+  LT_LOG("finished saving download : download:%p path:%s", request.second.download, request.second.path.c_str());
+  return false;
+}
+
+void
+SessionManager::flush_shutdown_saves() {
+  assert(torrent::this_thread::thread() == torrent::main_thread::thread());
+  flush_all_pending_builds();
+  std::unique_lock<std::mutex> lock(m_mutex);
+  flush_all_and_wait_unsafe(lock);
+}
+
 void
 SessionManager::flush_all_and_wait_unsafe(std::unique_lock<std::mutex>& lock) {
   LT_LOG("flushing all pending saves", 0);
@@ -459,11 +481,20 @@ SessionManager::flush_all_and_wait_unsafe(std::unique_lock<std::mutex>& lock) {
   while (!m_processing_saves.empty())
     m_finished_condition.wait(lock);
 
+  unsigned int suppressed = 0;
   for (auto& request : m_finished_saves)
-    LT_LOG("finished saving download : download:%p path:%s", request.second.download, request.second.path.c_str());
+    suppressed += consume_finished_save_unsafe(request) ? 1 : 0;
 
   m_finished_saves.clear();
 
+  // Report and reset here; a later session-thread pass would otherwise fold
+  // these into its own count. Name the two counts apart.
+  if (m_ignored_storage_error_count != 0) {
+    lt_log_print(torrent::LOG_ERRORS, "Storage errors flushing session data: ignored:%u, earlier ignored:%u",
+                 suppressed, m_ignored_storage_error_count - suppressed);
+    m_ignored_storage_error_count = 0;
+  }
+
   LT_LOG("flushed all pending saves", 0);
 }
 

src/session/session_manager.h

@@ -73,6 +73,7 @@ protected:
   void                cleanup();
 
   void                flush_all_pending_builds();
+  void                flush_shutdown_saves();
 
 private:
   void                callback_pending_builds();
@@ -92,6 +93,9 @@ private:
 
   using ProcessingSave = std::pair<std::future<void>, SaveRequest>;
 
+  bool                consume_finished_save_unsafe(ProcessingSave& request);
+  bool                report_storage_error_unsafe(const std::string& what);
+
   torrent::system::Thread*     m_thread;
   torrent::system::callback_id m_callback_id;