[Fix] suppress remote weight loading engine w/o mooncake installed (#14937)

python/sglang/srt/server_args.py

@@ -2226,6 +2226,8 @@ class ServerArgs:
             self.skip_server_warmup = True
 
     def _handle_remote_instance_weight_loader_support_transfer_engine(self):
+        try:
+            importlib.import_module("mooncake")
             if importlib.util.find_spec("mooncake.engine") is None:
                 logger.warning(
                     f"Failed to import mooncake.engine. Does not support using TransferEngine as remote instance weight loader backend."
@@ -2238,6 +2240,11 @@ class ServerArgs:
                 self.remote_instance_weight_loader_support_transfer_engine = False
             else:
                 self.remote_instance_weight_loader_support_transfer_engine = True
+        except ImportError:
+            logger.warning(
+                f"Failed to import mooncake. Does not support using TransferEngine as remote instance weight loader backend."
+            )
+            self.remote_instance_weight_loader_support_transfer_engine = False
 
     @staticmethod
     def add_cli_args(parser: argparse.ArgumentParser):