/*! Wait till processing thead has finished.
\return 0 on success */
int join() { return _pmodel == pm_pipeline ? _thread.join() : -1; }
/*! Wait till processing thead has finished.
\return 0 on success */
int join() { return _thread.join(); }
/// Join timer thread. Wait till exits.
void join() { _thread.join(); }
/// Stop the logging thread.
void stop() { _stopping = true; send(std::string()); _thread.join(); }
/*! Wait till processing thead has finished.
\return 0 on success */
int join() { return _pipelined ? _thread.join() : -1; }