feat: b64 encoding for nixl_connect metadata (#3843)

lib/bindings/python/src/dynamo/nixl_connect/__init__.py

@@ -16,6 +16,7 @@
 from __future__ import annotations
 
 import asyncio
+import base64
 import logging
 import socket
 import uuid
@@ -1185,7 +1186,7 @@ class PassiveOperation(AbstractOperation):
                 case _:
                     return
 
-    def metadata(self) -> RdmaMetadata:
+    def metadata(self, hex_encode: bool = False) -> RdmaMetadata:
         """
         Gets the request descriptor for the operation.
         """
@@ -1209,9 +1210,14 @@ class PassiveOperation(AbstractOperation):
                     f"dynamo.nixl_connect.{self.__class__.__name__}: Compressed NIXL metadata is larger than original ({compressed_len} > {original_len})."
                 )
 
+            if not hex_encode:
+                encoded_metadata = base64.b64encode(nixl_metadata).decode("utf-8")
+                encoded_metadata = "b64:" + encoded_metadata
+            else:
+                encoded_metadata = nixl_metadata.hex()
             self._serialized_request = RdmaMetadata(
                 descriptors=descriptors,
-                nixl_metadata=nixl_metadata.hex(),
+                nixl_metadata=encoded_metadata,
                 notification_key=self._notification_key,
                 operation_kind=int(self._operation_kind),
             )
@@ -1471,10 +1477,14 @@ class Remote:
         self._connector = connector
 
         # When `nixl_metadata` is a string, it is assumed to have come from a remote worker
-        # via a `RdmaMetadata` object and therefore can assumed be a hex-encoded, compressed
+        # via a `RdmaMetadata` object and therefore can assumed be a b64-encoded, compressed
         # representation of the NIXL metadata.
         if isinstance(nixl_metadata, str):
-            # Decode the hex-encoded string into bytes.
+            if nixl_metadata.startswith("b64:"):
+                # Decode the b64-encoded string into bytes.
+                nixl_metadata = base64.b64decode(nixl_metadata.lstrip("b64:"))
+            else:
+                # fallback for earlier versions of nixl connect
                 nixl_metadata = bytes.fromhex(nixl_metadata)
             # Decompress the NIXL metadata.
             nixl_metadata = zlib.decompress(nixl_metadata)