Add on_write_progress

design.md

@@ -105,7 +105,6 @@ See `config.md` for complete configuration documentation.
 - **Safe shutdown mechanism** with async-signal-safe shutdown() method
 - **Connection ownership management** with automatic cleanup on server destruction
 - **Pluggable protocol handlers** via ConnectionHandler interface
-- TODO design a way to stream server sent events
 
 Key features:
 - Multi-threaded architecture: separate accept and network thread pools
@@ -135,7 +134,7 @@ Key features:
 - **Connection lifecycle hooks** for initialization and cleanup
 
 Key features:
-- process_data() with unique_ptr<Connection>& for ownership transfer
+- on_data_arrived()/on_write_progress() with unique_ptr<Connection>& for ownership transfer
 - on_connection_established/closed() hooks for protocol state management
 - Zero-copy data processing with arena allocator integration
 - Thread-safe ownership transfer via Server::releaseBackToServer()
@@ -282,7 +281,7 @@ The modular design allows each component to be optimized independently while mai
 
 ### Adding New Protocol Handlers
 - Inherit from `ConnectionHandler` in `src/connection_handler.hpp`
-- Implement `process_data()` with proper ownership semantics
+- Implement `on_data_arrived()` with proper ownership semantics
 - Use connection's arena allocator for temporary allocations: `conn->getArena()`
 - Handle partial messages and streaming protocols appropriately
 - Use `Server::releaseBackToServer()` if taking ownership for async processing
@@ -338,7 +337,7 @@ auto server = Server::create(config, handler);
 ```cpp
 class HttpHandler : public ConnectionHandler {
 public:
-  void process_data(std::string_view data, std::unique_ptr<Connection>& conn_ptr) override {
+  void on_data_arrived(std::string_view data, std::unique_ptr<Connection>& conn_ptr) override {
     // Parse HTTP request using connection's arena
     ArenaAllocator& arena = conn_ptr->getArena();
 
@@ -354,7 +353,7 @@ public:
 ```cpp
 class AsyncHandler : public ConnectionHandler {
 public:
-  void process_data(std::string_view data, std::unique_ptr<Connection>& conn_ptr) override {
+  void on_data_arrived(std::string_view data, std::unique_ptr<Connection>& conn_ptr) override {
     // Take ownership for async processing
     auto connection = std::move(conn_ptr); // conn_ptr is now null
 
@@ -369,6 +368,8 @@ public:
 };
 ```
 
+TODO add example of streaming data
+
 ### Arena-Based String Handling
 ```cpp
 // Preferred: Zero-copy string view with arena allocation

src/connection.cpp

@@ -122,7 +122,7 @@ bool Connection::writeBytes() {
   // This reclaims memory from request parsing and response generation
   arena_.reset();
 
-  return closeConnection_;
+  return false;
 }
 
 void Connection::tsan_acquire() {

src/connection.hpp

@@ -44,6 +44,13 @@ struct Connection {
   void closeAfterSend() { closeConnection_ = true; }
   ArenaAllocator &getArena() { return arena_; }
   int64_t getId() const { return id_; }
+  int64_t outgoingBytesQueued() const {
+    int64_t result = 0;
+    for (auto s : messages_) {
+      result += s.size();
+    }
+    return result;
+  }
 
   // Note: To release connection back to server, use
   // Server::releaseBackToServer(std::move(connection_ptr))

src/connection_handler.hpp

@@ -35,12 +35,18 @@ public:
    * - If ownership is taken, handler must call Server::releaseBackToServer()
    * when done
    * @note `data` is *not* owned by the connection arena, and its lifetime ends
-   * after the call to process_data.
+   * after the call to on_data_arrived.
    * @note May be called from an arbitrary network thread.
    */
-  virtual void process_data(std::string_view data,
+  virtual void on_data_arrived(std::string_view data,
                                std::unique_ptr<Connection> &conn_ptr) = 0;
 
+  /**
+   * Successfully wrote data on the connection.
+   * @note May be called from an arbitrary network thread.
+   */
+  virtual void on_write_progress(std::unique_ptr<Connection> &) {}
+
   /**
    * Called when a new connection is established.
    *

src/main.cpp

@@ -29,7 +29,7 @@ void signal_handler(int sig) {
  */
 class EchoHandler : public ConnectionHandler {
 public:
-  void process_data(std::string_view data,
+  void on_data_arrived(std::string_view data,
                        std::unique_ptr<Connection> &conn_ptr) override {
     // Echo the received data back to the client
     conn_ptr->appendMessage(data);

src/server.cpp

@@ -270,7 +270,7 @@ void Server::start_network_threads() {
 
             // Call handler with unique_ptr - handler can take ownership if
             // needed
-            handler_.process_data(data, conn);
+            handler_.on_data_arrived(data, conn);
 
             // If handler took ownership (conn is now null), don't continue
             // processing
@@ -280,8 +280,22 @@ void Server::start_network_threads() {
           }
 
           if (events[i].events & EPOLLOUT) {
-            bool done = conn->writeBytes();
-            if (done) {
+            bool error = conn->writeBytes();
+            if (error) {
+              continue;
+            }
+
+            // Call handler with unique_ptr - handler can take ownership if
+            // needed
+            handler_.on_write_progress(conn);
+            // If handler took ownership (conn is now null), don't continue
+            // processing
+            if (!conn) {
+              continue;
+            }
+
+            // Check if we should close the connection according to application
+            if (!conn->hasMessages() && conn->closeConnection_) {
               continue;
             }
           }