ibzib commented on a change in pull request #12637:
URL: https://github.com/apache/beam/pull/12637#discussion_r492386778
##########
File path: sdks/python/apache_beam/runners/worker/data_plane_test.py
##########
@@ -108,16 +106,28 @@ def send(instruction_id, transform_id, data):
])
# Multiple interleaved writes to multiple instructions.
- send('1', transform_1, b'abc')
- send('2', transform_1, b'def')
+ stream11 = from_channel.output_stream('1', transform_1)
+ stream11.write(b'abc')
+ stream21 = from_channel.output_stream('2', transform_1)
+ stream21.write(b'def')
+ if not time_based_flush:
+ stream11.close()
self.assertEqual(
list(
itertools.islice(to_channel.input_elements('1', [transform_1]),
1)),
[
beam_fn_api_pb2.Elements.Data(
instruction_id='1', transform_id=transform_1, data=b'abc')
])
- send('2', transform_2, b'ghi')
+ if time_based_flush:
Review comment:
Write does not provide ordering guarantees in this case.
Elements are stored in a
[queue](https://github.com/apache/beam/blob/7b3d4251d244c10545fb37f1d93ebcad84a98681/sdks/python/apache_beam/runners/worker/data_plane.py#L371)
before being sent, to enable batching. Elements aren't added to that queue
until the [flush
callback](https://github.com/apache/beam/blob/7b3d4251d244c10545fb37f1d93ebcad84a98681/sdks/python/apache_beam/runners/worker/data_plane.py#L493)
is invoked. Because the flush callback is [invoked
periodically](https://github.com/apache/beam/blob/7b3d4251d244c10545fb37f1d93ebcad84a98681/sdks/python/apache_beam/runners/worker/data_plane.py#L182)
starting from when a stream is constructed, there is no guarantee that one
stream's callback is called before the other.
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