Support dynamic loading of external KV connector implementations

Added a new 'kv_connector_module_path' field to KVTransferConfig.
If a connector name is not found in the internal registry, the factory
will now attempt to load it dynamically using the provided module path

Signed-off-by: David Ben-David <davidb@pliops.com>

Author: David Ben-David

vllm/config.py

@@ -3491,6 +3491,10 @@ class KVTransferConfig:
     """The KV connector for vLLM to transmit KV caches between vLLM instances.
     """
 
+    kv_connector_module_path: Optional[str] = None
+    """The Python module path to dynamically load the KV connector from.
+    Only supported in V1."""
+
     engine_id: str = str(uuid.uuid4())
     """The engine id for KV transfers."""
 

vllm/distributed/kv_transfer/kv_connector/factory.py

@@ -58,8 +58,17 @@ def create_connector_v1(
             raise ValueError("Attempting to initialize a V1 Connector, "
                              f"but found {envs.VLLM_USE_V1=}")
 
-        connector_name = config.kv_transfer_config.kv_connector
-        connector_cls = cls._registry[connector_name]()
+        kv_transfer_config = config.kv_transfer_config
+        connector_name = kv_transfer_config.kv_connector
+        if connector_name in cls._registry:
+            connector_cls = cls._registry[connector_name]()
+        else:
+            connector_module_path = kv_transfer_config.kv_connector_module_path
+            if connector_module_path is None:
+                raise ValueError(
+                    f"Unsupported connector type: {connector_name}")
+            connector_module = importlib.import_module(connector_module_path)
+            connector_cls = getattr(connector_module, connector_name)
         assert issubclass(connector_cls, KVConnectorBase_V1)
         logger.info("Creating v1 connector with name: %s", connector_name)
         # NOTE(Kuntai): v1 connector is explicitly separated into two roles.