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feat: b64 encoding for nixl_connect metadata #3843

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feat: b64 encoding for nixl_connect metadata #3843

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b864ef3
feat: b64 encoding for nixl_connect metadata
milesial Oct 23, 2025
3b39604
feat: Add fallback to hex for compatibility
milesial Oct 23, 2025
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20 changes: 15 additions & 5 deletions lib/bindings/python/src/dynamo/nixl_connect/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
from __future__ import annotations

import asyncio
import base64
import logging
import socket
import uuid
Expand Down Expand Up @@ -1185,7 +1186,7 @@ async def _wait_for_completion_(self) -> None:
case _:
return

def metadata(self) -> RdmaMetadata:
def metadata(self, hex_encode: bool = False) -> RdmaMetadata:
"""
Gets the request descriptor for the operation.
"""
Expand All @@ -1209,9 +1210,14 @@ def metadata(self) -> RdmaMetadata:
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),
)
Expand Down Expand Up @@ -1471,11 +1477,15 @@ def __init__(
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.
nixl_metadata = bytes.fromhex(nixl_metadata)
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while b64 encoding is a win in size, we cannot just change the encoding and walk away.

please add a method to fallback to hex encoding to retain compatability.

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Added a fallback to hex in case people work with mismatched nixl_connect versions.

In some cases b64 and hex data cannot be distinguished so I added a small identifiable prefix for the new b64 encoding.

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)

Expand Down
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