Add kafka json to arrow support (#50)

beavers/pyarrow_kafka.py

@@ -0,0 +1,49 @@
+import dataclasses
+import io
+import json
+
+import confluent_kafka
+import pyarrow as pa
+import pyarrow.json
+
+from beavers.kafka import (
+    KafkaMessageDeserializer,
+    KafkaMessageSerializer,
+    KafkaProducerMessage,
+)
+
+
+@dataclasses.dataclass(frozen=True)
+class JsonDeserializer(KafkaMessageDeserializer[pa.Table]):
+    schema: pa.Schema
+
+    def __call__(self, messages: confluent_kafka.Message) -> pa.Table:
+        if messages:
+            with io.BytesIO() as buffer:
+                for message in messages:
+                    buffer.write(message.value())
+                    buffer.write(b"\n")
+                buffer.seek(0)
+                return pyarrow.json.read_json(
+                    buffer,
+                    parse_options=pyarrow.json.ParseOptions(
+                        explicit_schema=self.schema
+                    ),
+                )
+        else:
+            return self.schema.empty_table()
+
+
+@dataclasses.dataclass(frozen=True)
+class JsonSerializer(KafkaMessageSerializer[pa.Table]):
+    topic: str
+
+    def __call__(self, table: pa.Table):
+        return [
+            KafkaProducerMessage(
+                self.topic,
+                key=None,
+                value=json.dumps(message, default=str).encode("utf-8"),
+            )
+            for message in table.to_pylist()
+        ]

tests/test_pyarrow_kafka.py

@@ -0,0 +1,18 @@
+from beavers.pyarrow_kafka import JsonDeserializer, JsonSerializer
+from tests.test_kafka import mock_kafka_message
+from tests.test_util import TEST_TABLE
+
+
+def test_json_deserializer_empty():
+    deserializer = JsonDeserializer(TEST_TABLE.schema)
+    assert deserializer([]) == TEST_TABLE.schema.empty_table()
+
+
+def test_end_to_end():
+    deserializer = JsonDeserializer(TEST_TABLE.schema)
+    serializer = JsonSerializer("topic-1")
+    out_messages = serializer(TEST_TABLE)
+    in_messages = [
+        mock_kafka_message(topic=m.topic, value=m.value) for m in out_messages
+    ]
+    assert deserializer(in_messages) == TEST_TABLE

tests/test_pyarrow_replay.py

@@ -7,16 +7,7 @@
 
 from beavers.engine import UTC_MAX
 from beavers.pyarrow_replay import ArrowTableDataSink, ArrowTableDataSource
-
-TEST_TABLE = pa.table(
-    {
-        "timestamp": [
-            pd.to_datetime("2023-01-01T00:00:00Z"),
-            pd.to_datetime("2023-01-02T00:00:00Z"),
-        ],
-        "value": [1, 2],
-    }
-)
+from tests.test_util import TEST_TABLE
 
 
 def test_arrow_table_data_source():

tests/test_util.py

@@ -4,12 +4,23 @@
 from typing import Callable, Dict, Generic, TypeVar
 
 import pandas as pd
+import pyarrow as pa
 
 from beavers.engine import UTC_MAX, Dag, TimerManager
 from beavers.replay import DataSink, DataSource
 
 T = TypeVar("T")
 
+TEST_TABLE = pa.table(
+    {
+        "timestamp": [
+            pd.to_datetime("2023-01-01T00:00:00Z"),
+            pd.to_datetime("2023-01-02T00:00:00Z"),
+        ],
+        "value": [1, 2],
+    }
+)
+
 
 class GetLatest(Generic[T]):
     def __init__(self, default: T):