Support pause/resume in single-transaction downloads

Signed-off-by: Anton Gerasimov <anton.gerasimov@here.com>

src/libaktualizr/primary/aktualizr.cc

@@ -94,6 +94,7 @@ void Aktualizr::AddSecondary(const std::shared_ptr<Uptane::SecondaryInterface> &
 
 void Aktualizr::Shutdown() {
   if (!shutdown_) {
+    uptane_client_->pause();
     shutdown_ = true;
     api_queue_.shutDown();
   }

src/libaktualizr/primary/aktualizr_test.cc

@@ -73,7 +73,7 @@ void process_events_FullNoUpdates(const std::shared_ptr<event::BaseEvent>& event
       FAIL();
     default:
       std::cout << "event #" << num_events_FullNoUpdates << " is: " << event->variant << "\n";
-      EXPECT_EQ(event->variant, "");
+      EXPECT_TRUE((event->variant == "") || (event->variant == "DownloadPaused"));
   }
   ++num_events_FullNoUpdates;
 }
@@ -234,7 +234,7 @@ void process_events_FullWithUpdates(const std::shared_ptr<event::BaseEvent>& eve
       FAIL();
     default:
       std::cout << "event #" << num_events_FullWithUpdates << " is: " << event->variant << "\n";
-      EXPECT_EQ(event->variant, "");
+      EXPECT_TRUE((event->variant == "") || (event->variant == "DownloadPaused"));
   }
   ++num_events_FullWithUpdates;
 }
@@ -422,11 +422,15 @@ void process_events_FullMultipleSecondaries(const std::shared_ptr<event::BaseEve
     allcomplete_FullMultipleSecondaries = true;
   } else if (event->variant == "PutManifestComplete") {
     manifest_FullMultipleSecondaries = true;
+  } else if (event->variant == "DownloadPaused") {
+    // phony event on shutdown, ignore
+    return;
   }
   // It is possible for the PutManifestComplete to come before we get the
   // InstallTargetComplete depending on the threading, so check for both.
   if (allcomplete_FullMultipleSecondaries && complete_FullMultipleSecondaries == 2 &&
       manifest_FullMultipleSecondaries) {
+    LOG_ERROR << "SETVALUE";
     promise_FullMultipleSecondaries.set_value();
   }
 }
@@ -504,7 +508,7 @@ void process_events_CheckWithUpdates(const std::shared_ptr<event::BaseEvent>& ev
       FAIL();
     default:
       std::cout << "event #" << num_events_CheckWithUpdates << " is: " << event->variant << "\n";
-      EXPECT_EQ(event->variant, "");
+      EXPECT_TRUE((event->variant == "") || (event->variant == "DownloadPaused"));
   }
   ++num_events_CheckWithUpdates;
 }
@@ -589,7 +593,7 @@ void process_events_DownloadWithUpdates(const std::shared_ptr<event::BaseEvent>&
       FAIL();
     default:
       std::cout << "event #" << num_events_DownloadWithUpdates << " is: " << event->variant << "\n";
-      EXPECT_EQ(event->variant, "");
+      EXPECT_TRUE((event->variant == "") || (event->variant == "DownloadPaused"));
   }
   ++num_events_DownloadWithUpdates;
 }
@@ -731,7 +735,7 @@ void process_events_InstallWithUpdates(const std::shared_ptr<event::BaseEvent>&
       FAIL();
     default:
       std::cout << "event #" << num_events_InstallWithUpdates << " is: " << event->variant << "\n";
-      EXPECT_EQ(event->variant, "");
+      EXPECT_TRUE((event->variant == "") || (event->variant == "DownloadPaused"));
   }
   ++num_events_InstallWithUpdates;
 }

src/libaktualizr/uptane/fetcher.cc

@@ -132,7 +132,16 @@ bool Fetcher::fetchVerifyTarget(const Target& target) {
           throw Exception("image", "Could not download file, error: " + response.error_message);
         }
         if (pause_) {
-          std::lock_guard<std::mutex> lock(*pause_mutex_);
+          // entering pause, save the file and free the handler
+          ds.fhandle->wcommit();
+          fhandle.reset();
+
+          std::lock_guard<std::mutex> lock(*pause_mutex_);  // waiting on this mutex while paused
+
+          // exiting pause, restore the file context
+          auto target_handle = storage->openTargetFile(target);
+          fhandle = target_handle->toWriteHandle();
+          ds.fhandle = fhandle.get();
           retry = true;
         }
       } while (retry);