Reintroduce cache file as it is still required for "lastUpdate" for DBs

Maybe it makes more sense to use LMDB for this as well. On the other hand
it is an easy way of keeping the remaining state persistent.

librepomgr/CMakeLists.txt

@@ -71,6 +71,7 @@ set(META_APP_DESCRIPTION "Library for managing custom Arch Linux repositories")
 set(META_VERSION_MAJOR 0)
 set(META_VERSION_MINOR 0)
 set(META_VERSION_PATCH 1)
+set(META_VERSION_CACHE 11)
 set(LINK_TESTS_AGAINST_APP_TARGET ON)
 
 # find c++utilities
@@ -117,6 +118,9 @@ list(APPEND PUBLIC_LIBRARIES pthread)
 # apply basic configuration
 include(BasicConfig)
 
+# add cache version to config header
+string(APPEND META_CUSTOM_CONFIG "#define ${META_PROJECT_VARNAME}_CACHE_VERSION \"${META_VERSION_CACHE}\"\n")
+
 # trigger code generator for tests because the tests already contain structs to be (de)serialized
 include(ReflectionGenerator)
 add_reflection_generator_invocation(

librepomgr/buildactions/reloaddatabase.cpp

@@ -41,6 +41,12 @@ void ReloadDatabase::run()
 
     auto session
         = WebClient::DatabaseQuerySession::create(m_setup.building.ioContext, [this](WebClient::DatabaseQuerySession::ContainerType &&failedDbs) {
+              // save state for "lastUpdate" timestamps
+              auto configReadLock2 = m_setup.config.lockToRead();
+              m_setup.saveState();
+              configReadLock2.unlock();
+
+              // conclude build action
               if (!m_preparationFailures.empty()) {
                   mergeSecondVectorIntoFirstVector(failedDbs, m_preparationFailures);
               }

librepomgr/serversetup.cpp

@@ -555,8 +555,32 @@ void ServiceSetup::printDatabases()
     cerr << Phrases::SubMessage << "AUR (" << config.aur.packageCount() << " packages cached)" << Phrases::End;
 }
 
+std::string_view ServiceSetup::cacheFilePath() const
+{
+    return "cache-v" LIBREPOMGR_CACHE_VERSION ".bin";
+}
+
 void ServiceSetup::restoreState()
 {
+    // restore configuration and maybe build actions from JSON file
+    const auto cacheFilePath = this->cacheFilePath();
+    auto size = std::size_t(0);
+    try {
+        auto cacheFile = std::fstream();
+        cacheFile.exceptions(std::ios_base::failbit | std::ios_base::badbit);
+        cacheFile.open(cacheFilePath.data(), std::ios_base::in | std::ios_base::binary);
+        auto deserializer = ReflectiveRapidJSON::BinaryReflector::BinaryDeserializer(&cacheFile);
+        deserializer.read(config);
+        size = static_cast<std::uint64_t>(cacheFile.tellg());
+        cacheFile.close();
+        std::cerr << Phrases::SuccessMessage << "Restored cache file \"" << cacheFilePath << "\", " << dataSizeToString(size) << Phrases::EndFlush;
+    } catch (const ConversionException &) {
+        std::cerr << Phrases::WarningMessage << "A conversion error occurred when restoring cache file \"" << cacheFilePath << "\"."
+                  << Phrases::EndFlush;
+    } catch (const ios_base::failure &) {
+        std::cerr << Phrases::WarningMessage << "An IO error occurred when restoring cache file \"" << cacheFilePath << "\"." << Phrases::EndFlush;
+    }
+
     // open LMDB storage
     cout << Phrases::InfoMessage << "Opening config LMDB file: " << dbPath << " (max DBs: " << maxDbs << ')' << Phrases::EndFlush;
     config.initStorage(dbPath.data(), maxDbs);
@@ -580,6 +604,26 @@ void ServiceSetup::restoreState()
     });
 }
 
+std::size_t ServiceSetup::saveState()
+{
+    // write cache file to be able to restore the service state when restarting the service efficiently
+    const auto cacheFilePath = this->cacheFilePath();
+    auto size = std::size_t(0);
+    try {
+        auto cacheFile = std::fstream();
+        cacheFile.exceptions(std::ios_base::failbit | std::ios_base::badbit);
+        cacheFile.open(cacheFilePath.data(), std::ios_base::out | std::ios_base::trunc | std::ios_base::binary);
+        auto serializer = ReflectiveRapidJSON::BinaryReflector::BinarySerializer(&cacheFile);
+        serializer.write(config);
+        size = static_cast<std::uint64_t>(cacheFile.tellp());
+        cacheFile.close();
+        std::cerr << Phrases::SuccessMessage << "Wrote cache file \"" << cacheFilePath << "\", " << dataSizeToString(size) << Phrases::EndFlush;
+    } catch (const ios_base::failure &) {
+        std::cerr << Phrases::WarningMessage << "An IO error occurred when dumping the cache file \"" << cacheFilePath << "\"." << Phrases::EndFlush;
+    }
+    return size;
+}
+
 void ServiceSetup::initStorage()
 {
     restoreState();
@@ -627,6 +671,8 @@ void ServiceSetup::run()
 #endif
     }
 
+    saveState();
+
     building.forEachBuildAction([](LibPkg::StorageID, BuildAction &buildAction, bool &save) {
         if (buildAction.isExecuting()) {
             buildAction.status = BuildActionStatus::Finished;

librepomgr/serversetup.h

@@ -49,7 +49,9 @@ struct LIBREPOMGR_EXPORT ServiceSetup : public LibPkg::Lockable {
 
     void loadConfigFiles(bool doFirstTimeSetup);
     void printDatabases();
+    std::string_view cacheFilePath() const;
     void restoreState();
+    std::size_t saveState();
     void initStorage();
     void run();
     ServiceStatus computeStatus() const;