Prevent queueing of messages on connection after it will be closed

src/connection.hpp

@@ -109,11 +109,15 @@ struct Connection : MessageSender {
    *
    * @param data_parts Span of string_views pointing to arena-allocated data
    * @param arena Arena that owns all the memory referenced by data_parts
-   * @param close_after_send Whether to close connection after sending
+   * @param close_after_send Whether to close connection after sending all
+   * queued data
    *
    * @note Thread Safety: Must be called from I/O thread only.
    * @note Ordering: Bytes are sent in the order calls are made.
    * @note The memory referenced by the data_parts span, must outlive @p arena.
+   * @note Close Request: To request connection close without sending data,
+   *       pass empty data_parts span with close_after_send=true. This ensures
+   *       all previously queued messages are sent before closing.
    *
    * Example usage (from ConnectionHandler::on_preprocess_writes):
    * ```cpp
@@ -289,7 +293,6 @@ private:
     Arena arena;                            // Owns all the memory (movable)
     std::span<std::string_view> data_parts; // Points to arena-allocated memory
                                             // (mutable for partial writes)
-    bool close_after_send = false;          // Close connection after sending
   };
 
   // Server is a friend and can access all networking internals
@@ -343,7 +346,8 @@ private:
                       // dropped while server accesses existing elements.
   int64_t outgoing_bytes_queued_{0}; // Counter of queued bytes
   std::deque<PendingResponse>
-      pending_response_queue_; // Responses awaiting protocol processing
+      pending_response_queue_;  // Responses awaiting protocol processing
+  bool close_requested_{false}; // True if close_after_send has been requested
   // Set to a negative number in `close`
   int fd_;