Implement shutting down the write-side only

src/connection.hpp

@@ -20,6 +20,15 @@
 // Forward declaration
 struct Server;
 
+/**
+ * Shutdown modes for connection termination.
+ */
+enum class ConnectionShutdown {
+  None,      // Normal operation - no shutdown requested
+  WriteOnly, // shutdown(SHUT_WR) after sending queued data
+  Full       // close() after sending queued data
+};
+
 /**
  * Base interface for sending messages to a connection.
  * This restricted interface is safe for use by pipeline threads,
@@ -109,15 +118,14 @@ 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 all
-   * queued data
+   * @param shutdown_mode Shutdown mode to apply 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.
+   * @note Shutdown Request: To request connection shutdown without sending
+   * data, pass empty data_parts span with desired shutdown_mode. This ensures
+   *       all previously queued messages are sent before shutdown.
    *
    * Example usage (from ConnectionHandler::on_preprocess_writes):
    * ```cpp
@@ -125,11 +133,12 @@ struct Connection : MessageSender {
    * auto parts = arena.allocate_span<std::string_view>(2);
    * parts[0] = build_header(arena);
    * parts[1] = build_body(arena);
-   * conn.append_bytes({parts, 2}, std::move(arena), false);
+   * conn.append_bytes({parts, 2}, std::move(arena), ConnectionShutdown::None);
    * ```
    */
-  void append_bytes(std::span<std::string_view> data_parts, Arena arena,
-                    bool close_after_send);
+  void
+  append_bytes(std::span<std::string_view> data_parts, Arena arena,
+               ConnectionShutdown shutdown_mode = ConnectionShutdown::None);
 
   void send_response(void *protocol_context, std::string_view response_json,
                      Arena arena) override;
@@ -346,8 +355,9 @@ 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
-  bool close_requested_{false}; // True if close_after_send has been requested
+      pending_response_queue_; // Responses awaiting protocol processing
+  ConnectionShutdown shutdown_requested_{
+      ConnectionShutdown::None}; // Shutdown mode requested
   // Set to a negative number in `close`
   int fd_;