use binary encoder

Author: rnpridgeon

confluent_kafka/avro/serializer/message_serializer.py

@@ -80,7 +80,7 @@ def _get_encoder_func(self, writer_schema):
         if HAS_FAST:
             schema = writer_schema.to_json()
             return lambda record, fp: schemaless_writer(fp, schema, record)
-        return avro.io.DatumWriter(writer_schema).write
+        return lambda record, fp: avro.io.DatumWriter(writer_schema).write(record, avro.io.BinaryEncoder(fp))
 
     def encode_record_with_schema(self, topic, schema, record, is_key=False):
         """