Support server based rollout in Verlengine (#4848)

Co-authored-by: Jin Pan <jpan236@wisc.edu>
Co-authored-by: Chayenne <zhaochen20@outlook.com>
Co-authored-by: Jinn <47354855+jhinpan@users.noreply.github.com>

python/sglang/srt/utils.py

@@ -1480,14 +1480,43 @@ def permute_weight(x: torch.Tensor) -> torch.Tensor:
 
 class MultiprocessingSerializer:
     @staticmethod
-    def serialize(obj):
+    def serialize(obj, output_str: bool = False):
+        """
+        Serialize a Python object using ForkingPickler.
+
+        Args:
+            obj: The object to serialize.
+            output_str (bool): If True, return a base64-encoded string instead of raw bytes.
+
+        Returns:
+            bytes or str: The serialized object.
+        """
         buf = io.BytesIO()
         ForkingPickler(buf).dump(obj)
         buf.seek(0)
-        return buf.read()
+        output = buf.read()
+
+        if output_str:
+            # Convert bytes to base64-encoded string
+            output = base64.b64encode(output).decode("utf-8")
+
+        return output
 
     @staticmethod
     def deserialize(data):
+        """
+        Deserialize a previously serialized object.
+
+        Args:
+            data (bytes or str): The serialized data, optionally base64-encoded.
+
+        Returns:
+            The deserialized Python object.
+        """
+        if isinstance(data, str):
+            # Decode base64 string to bytes
+            data = base64.b64decode(data)
+
         return ForkingPickler.loads(data)