Expose the flusher thread object to user in order to allow setting of thread name and thread affinity when needed

include/spdlog/details/periodic_worker.h

@@ -38,6 +38,7 @@ public:
             }
         });
     }
+    std::thread *get_thread() { return &worker_thread_; }
     periodic_worker(const periodic_worker &) = delete;
     periodic_worker &operator=(const periodic_worker &) = delete;
     // stop the worker thread and join it

include/spdlog/details/registry.h

@@ -68,6 +68,8 @@ public:
         periodic_flusher_ = details::make_unique<periodic_worker>(clbk, interval);
     }
 
+    std::unique_ptr<periodic_worker> &get_flusher() { return periodic_flusher_; }
+
     void set_error_handler(err_handler handler);
 
     void apply_all(const std::function<void(const std::shared_ptr<logger>)> &fun);

include/spdlog/spdlog-inl.h

@@ -89,4 +89,9 @@ SPDLOG_INLINE void apply_logger_env_levels(std::shared_ptr<logger> logger) {
     details::registry::instance().apply_logger_env_levels(std::move(logger));
 }
 
+SPDLOG_INLINE std::unique_ptr<spdlog::details::periodic_worker> &get_flusher()
+{
+    return details::registry::instance().get_flusher();
+}
+
 }  // namespace spdlog