Try writing once on connect thread

tools/load_tester.cpp

@@ -723,10 +723,30 @@ int main(int argc, char *argv[]) {
         auto conn = std::make_unique<Connection>(
             fd, connectionId.fetch_add(1, std::memory_order_relaxed));
 
-        // Add to epoll with proper events matching server pattern
-        struct epoll_event event{};
+        // Try to write once in the connect thread before handing off to network
+        // threads
         assert(conn->hasMessages());
-        event.events = EPOLLOUT | EPOLLONESHOT | EPOLLRDHUP;
+        bool writeFinished = conn->writeBytes();
+        if (conn->error) {
+          continue; // Connection failed, destructor will clean up
+        }
+
+        // Determine the appropriate epoll events based on write result
+        struct epoll_event event{};
+        if (writeFinished) {
+          // All data was written, wait for response
+          int shutdown_result = shutdown(conn->fd, SHUT_WR);
+          if (shutdown_result == -1) {
+            perror("shutdown");
+            continue;
+          }
+          event.events = EPOLLIN | EPOLLONESHOT | EPOLLRDHUP;
+        } else {
+          // Partial write, need to continue writing
+          event.events = EPOLLOUT | EPOLLONESHOT | EPOLLRDHUP;
+        }
+
+        // Add to epoll for network threads to handle remaining I/O
         conn->tsan_release();
         Connection *raw_conn = conn.release();
         event.data.ptr = raw_conn;