add kafka parameter explicitly and uncover kafka test for a try

Author: derrickaw

sdks/python/apache_beam/yaml/extended_tests/messaging/kafka.yaml

@@ -50,33 +50,33 @@ pipelines:
   # Locally runs fine.
   # Kafka read pipeline
   # Need a separate read pipeline to make sure the write pipeline is flushed
-  # - pipeline:
-  #     type: chain
-  #     transforms:
-  #       - type: ReadFromKafka
-  #         config:
-  #           format: "RAW"
-  #           topic: "silly_topic"
-  #           bootstrap_servers: "{TEMP_BOOTSTAP_SERVER}"
-  #           consumer_config:
-  #             auto.offset.reset: "earliest"
-  #             group.id: "yaml-kafka-test-group"
-  #           max_read_time_seconds: 10 # will read forever if not set
-  #       - type: MapToFields
-  #         config:
-  #           language: python
-  #           fields:
-  #             value:
-  #               callable: |
-  #                 # Kafka RAW format reads messages as bytes in the 'payload' field of a Row
-  #                 lambda row: row.payload.decode('utf-8')
-  #               output_type: string
-  #       - type: AssertEqual
-  #         config:
-  #           elements:
-  #             - {value: "123"}
-  #             - {value: "456"}
-  #             - {value: "789"}
+  - pipeline:
+      type: chain
+      transforms:
+        - type: ReadFromKafka
+          config:
+            format: "RAW"
+            topic: "silly_topic"
+            bootstrap_servers: "{TEMP_BOOTSTAP_SERVER}"
+            consumer_config:
+              auto.offset.reset: "earliest"
+              group.id: "yaml-kafka-test-group"
+            max_read_time_seconds: 10 # will read forever if not set
+        - type: MapToFields
+          config:
+            language: python
+            fields:
+              value:
+                callable: |
+                  # Kafka RAW format reads messages as bytes in the 'payload' field of a Row
+                  lambda row: row.payload.decode('utf-8')
+                output_type: string
+        - type: AssertEqual
+          config:
+            elements:
+              - {value: "123"}
+              - {value: "456"}
+              - {value: "789"}
 
     options:
       streaming: true

sdks/python/apache_beam/yaml/standard_io.yaml

@@ -74,6 +74,7 @@
         'error_handling': 'error_handling'
         'file_descriptor_path': 'file_descriptor_path'
         'message_name': 'message_name'
+        'max_read_time_seconds': 'max_read_time_seconds'
       'WriteToKafka':
         'format': 'format'
         'topic': 'topic'

sdks/python/apache_beam/yaml/yaml_provider.py

@@ -1510,6 +1510,8 @@ def create_transform(
     """Creates a PTransform instance for the given transform type and arguments.
     """
     mappings = self._mappings[typ]
+    # NOTE: If the `key` is not found in the mappings (e.g. standard_io.py), the
+    # `key` is passed down as is to the underlying transform.
     remapped_args = {
         mappings.get(key, key): value
         for key, value in args.items()