Method MultiVersionDatabase

fdbclient/MultiVersionTransaction.actor.cpp:1661–1720

MultiVersionDatabase

// MultiVersionDatabase
MultiVersionDatabase::MultiVersionDatabase(MultiVersionApi* api,
                                           int threadIdx,
                                           ClusterConnectionRecord const& connectionRecord,
                                           Reference<IDatabase> db,
                                           Reference<IDatabase> versionMonitorDb,
                                           bool openConnectors)
  : dbState(new DatabaseState(connectionRecord, versionMonitorDb)) {
	dbState->db = db;
	dbState->dbVar->set(db);
	if (openConnectors) {
		if (!api->localClientDisabled) {
			dbState->addClient(api->getLocalClient());
		}

		api->runOnExternalClients(threadIdx, [this](Reference<ClientInfo> client) { dbState->addClient(client); });

		api->runOnExternalClientsAllThreads([&connectionRecord](Reference<ClientInfo> client) {
			// This creates a database to initialize some client state on the external library.
			// We only do this on 6.2+ clients to avoid some bugs associated with older versions.
			// This deletes the new database immediately to discard its connections.
			//
			// Simultaneous attempts to create a database could result in us running this initialization
			// code in multiple threads simultaneously. It is necessary that each attempt have a chance
			// to run this initialization in case the other fails, and it's safe to run them in parallel.
			if (client->protocolVersion.hasCloseUnusedConnection() && !client->initialized) {
				try {
					Reference<IDatabase> newDb = connectionRecord.createDatabase(client->api);
					client->initialized = true;
				} catch (Error& e) {
					// This connection is not initialized. It is still possible to connect with it,
					// but we may not see trace logs from this client until a successful connection
					// is established.
					TraceEvent(SevWarnAlways, "FailedToInitializeExternalClient")
					    .error(e)
					    .detail("LibraryPath", client->libPath)
					    .detail("ConnectionRecord", connectionRecord);
				}
			}
		});

		// For clients older than 6.2 we create and maintain our database connection
		api->runOnExternalClients(threadIdx, [this, &connectionRecord](Reference<ClientInfo> client) {
			if (!client->protocolVersion.hasCloseUnusedConnection()) {
				try {
					dbState->legacyDatabaseConnections[client->protocolVersion] =
					    connectionRecord.createDatabase(client->api);
				} catch (Error& e) {
					// This connection is discarded
					TraceEvent(SevWarnAlways, "FailedToCreateLegacyDatabaseConnection")
					    .error(e)
					    .detail("LibraryPath", client->libPath)
					    .detail("ConnectionRecord", connectionRecord);
				}
			}
		});

		Reference<DatabaseState> dbStateRef = dbState;
		onMainThreadVoid([dbStateRef]() { dbStateRef->protocolVersionMonitor = dbStateRef->monitorProtocolVersion(); });