Add an index to thread pipeline iterators for load balancing

src/server.cpp

@@ -411,8 +411,8 @@ void Server::start_io_threads(std::vector<std::thread> &threads) {
   }
 }
 
-void Server::process_connection_io(std::unique_ptr<Connection> &conn,
-                                   int events) {
+void Server::process_connection_reads(std::unique_ptr<Connection> &conn,
+                                      int events) {
   assert(conn);
   // Handle EPOLLIN - read data and process it
   if (events & EPOLLIN) {
@@ -440,7 +440,11 @@ void Server::process_connection_io(std::unique_ptr<Connection> &conn,
       return;
     }
   }
+}
 
+void Server::process_connection_writes(std::unique_ptr<Connection> &conn,
+                                       int events) {
+  assert(conn);
   // Send immediately if we have outgoing messages (either from EPOLLOUT or
   // after reading)
   if ((events & EPOLLOUT) || ((events & EPOLLIN) && conn->hasMessages())) {
@@ -469,10 +473,18 @@ void Server::process_connection_io(std::unique_ptr<Connection> &conn,
 void Server::process_connection_batch(
     int epollfd, std::span<std::unique_ptr<Connection>> batch,
     std::span<const int> events) {
-  // First process I/O for each connection
+
+  // First process writes for each connection
   for (size_t i = 0; i < batch.size(); ++i) {
     if (batch[i]) {
-      process_connection_io(batch[i], events[i]);
+      process_connection_writes(batch[i], events[i]);
+    }
+  }
+
+  // Then process reads for each connection
+  for (size_t i = 0; i < batch.size(); ++i) {
+    if (batch[i]) {
+      process_connection_reads(batch[i], events[i]);
     }
   }