Maintain outgoing bytes queued count

src/connection.cpp

@@ -43,6 +43,7 @@ void Connection::appendMessage(std::string_view s, bool copy_to_arena) {
   } else {
     messages_.push_back(s);
   }
+  outgoing_bytes_queued_ += s.size();
 }
 
 int Connection::readBytes(char *buf, size_t buffer_size) {
@@ -104,6 +105,7 @@ bool Connection::writeBytes() {
 
     // Handle partial writes by updating string_view data/size
     size_t bytes_written = static_cast<size_t>(w);
+    outgoing_bytes_queued_ -= bytes_written;
     while (bytes_written > 0 && !messages_.empty()) {
       auto &front = messages_.front();