Do not do send in cache warmer -- just establish connections (#32898)

* Do not do send in cache warmer -- just establish connections

core/src/warm_quic_cache_service.rs

@@ -54,7 +54,7 @@ impl WarmQuicCacheService {
                                 .lookup_contact_info(&leader_pubkey, |node| node.tpu(Protocol::QUIC))
                             {
                                 let conn = connection_cache.get_connection(&addr);
-                                if let Err(err) = conn.send_data(&[0u8]) {
+                                if let Err(err) = conn.send_data(&[]) {
                                     warn!(
                                         "Failed to warmup QUIC connection to the leader {:?}, Error {:?}",
                                         leader_pubkey, err

quic-client/src/nonblocking/quic_client.rs

@@ -384,6 +384,11 @@ impl QuicClient {
                 .acks
                 .update_stat(&self.stats.acks, new_stats.frame_tx.acks);
 
+            if data.is_empty() {
+                // no need to send packet as it is only for warming connections
+                return Ok(connection);
+            }
+
             last_connection_id = connection.stable_id();
             match Self::_send_buffer_using_conn(data, &connection).await {
                 Ok(()) => {