Implement shutting down the write-side only

src/connection.cpp

@@ -89,7 +89,7 @@ void Connection::close() {
 
 // Called from I/O thread only
 void Connection::append_bytes(std::span<std::string_view> data_parts,
-                              Arena arena, bool close_after_send) {
+                              Arena arena, ConnectionShutdown shutdown_mode) {
   // Calculate total bytes for this message. Don't need to hold the lock yet.
   size_t total_bytes = 0;
   for (const auto &part : data_parts) {
@@ -98,17 +98,17 @@ void Connection::append_bytes(std::span<std::string_view> data_parts,
 
   std::unique_lock lock(mutex_);
 
-  // Prevent queueing messages after close has been requested
-  if (close_requested_) {
+  // Prevent queueing messages after shutdown has been requested
+  if (shutdown_requested_ != ConnectionShutdown::None) {
     return;
   }
 
   // Check if queue was empty to determine if we need to enable EPOLLOUT
   bool was_empty = message_queue_.empty();
 
-  // Set close_requested flag if this message requests close
-  if (close_after_send) {
-    close_requested_ = true;
+  // Set shutdown mode if requested
+  if (shutdown_mode != ConnectionShutdown::None) {
+    shutdown_requested_ = shutdown_mode;
   }
 
   // Add message to queue
@@ -137,8 +137,8 @@ void Connection::send_response(void *protocol_context,
                                std::string_view response_json, Arena arena) {
   std::unique_lock lock(mutex_);
 
-  // Prevent queueing responses after close has been requested
-  if (close_requested_) {
+  // Prevent queueing responses after shutdown has been requested
+  if (shutdown_requested_ != ConnectionShutdown::None) {
     return;
   }
 
@@ -307,7 +307,11 @@ uint32_t Connection::write_bytes() {
         // sets it and we would hang.
         epoll_ctl(server->epoll_fds_[epoll_index_], EPOLL_CTL_MOD, fd_, &event);
       }
-      if (close_requested_) {
+      // Handle shutdown modes after all messages are sent
+      if (shutdown_requested_ == ConnectionShutdown::WriteOnly) {
+        // Shutdown write side but keep connection alive for reading
+        shutdown(fd_, SHUT_WR);
+      } else if (shutdown_requested_ == ConnectionShutdown::Full) {
         result |= Close;
       }
     }

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_;
 

src/http_handler.cpp

@@ -522,7 +522,9 @@ void HttpConnectionState::send_ordered_response(
 
     // Send through append_bytes which handles write interest
     conn.append_bytes(response_data.data, std::move(response_data.arena),
-                      response_data.connection_close);
+                      response_data.connection_close
+                          ? ConnectionShutdown::Full
+                          : ConnectionShutdown::None);
     next_sequence_to_send++;
     iter = ready_responses.erase(iter);
   }

tests/test_server.cpp

@@ -39,7 +39,7 @@ TEST_CASE("Echo test") {
     // MessageSender)
     auto *conn_ptr = static_cast<Connection *>(conn.get());
     conn_ptr->append_bytes(std::exchange(handler.reply, {}),
-                           std::move(handler.arena), false);
+                           std::move(handler.arena), ConnectionShutdown::None);
   } else {
     REQUIRE(false);
   }