[PD] Add transfer backend abstraction (#5328)

python/sglang/srt/disaggregation/utils.py

@@ -42,3 +42,34 @@ class ReqToMetadataIdxAllocator:
 
     def free(self, free_index: int):
         self.free_slots.append(free_index)
+
+
+class TransferBackend(Enum):
+    MOONCAKE = "mooncake"
+    FAKE = "fake"
+
+
+class KVClassType(Enum):
+    MANAGER = "manager"
+    SENDER = "sender"
+    RECEIVER = "receiver"
+    BOOTSTRAP_SERVER = "bootstrap_server"
+
+
+def get_kv_class(transfer_backend: TransferBackend, class_type: KVClassType):
+    if transfer_backend == TransferBackend.MOONCAKE:
+        from sglang.srt.disaggregation.mooncake import (
+            MooncakeKVBootstrapServer,
+            MooncakeKVManager,
+            MooncakeKVReceiver,
+            MooncakeKVSender,
+        )
+
+        class_mapping = {
+            KVClassType.MANAGER: MooncakeKVManager,
+            KVClassType.SENDER: MooncakeKVSender,
+            KVClassType.RECEIVER: MooncakeKVReceiver,
+            KVClassType.BOOTSTRAP_SERVER: MooncakeKVBootstrapServer,
+        }
+        return class_mapping.get(class_type)
+    raise ValueError(f"Unsupported transfer backend: {transfer_backend}")