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Add Python example for slowly updating global window side inputs - #40183
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chamikaramj merged 2 commits intoSep 21, 2026
Merged
chamikaramj merged 2 commits into
chamikaramj merged 2 commits into
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The "Slowly updating global window side inputs" section of the side input patterns page only had a Java sample; the Python block said "No sample present.". This adds a Python counterpart to the Java sample in snippets.py, references it from the website with code_sample, and covers it with a unit test. The example uses PeriodicImpulse as a streaming source, re-publishes the external data into the global window on every firing with a repeated trigger and discarding panes, and reads the value with Latest.Globally().without_defaults(). The without_defaults() variant is required because the default variant adds its own side input, which stops the transform from emitting more than once (apache#35934). Addresses apache#35935
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chamikaramj
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Sep 18, 2026
| from apache_beam.transforms import window | ||
| from apache_beam.transforms.periodicsequence import PeriodicImpulse | ||
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| # from apache_beam.utils.timestamp import MAX_TIMESTAMP |
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Nit: pls remove commented out code.
| for i in range(-1, 10, 1): | ||
| os.unlink(src_file_pattern + str(first_ts + interval * i)) | ||
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| def test_side_input_slow_update_global_window(self): |
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Did we try the pipeline on Dataflow ? According to #35934 the behavior seems to be different for Dataflow.
| (expected_main_input_elements, main_input_elements)) | ||
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| side_input_values = set(value for _, value in actual) | ||
| assert side_input_values, 'No side input value was observed.' |
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This assertion might be passing trivially for (main input, side input) combinations (<valid value>, None). Try changing to:
side_input_values = set(value for _, value in actual)
assert None not in side_input_values, (
'Some elements were processed before the side input was ready.')
chamikaramj
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Sep 19, 2026
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I can merge when comments are resolved. Thanks!
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Assigning reviewers: R: @damccorm for label python. Note: If you would like to opt out of this review, comment Available commands:
The PR bot will only process comments in the main thread (not review comments). |
- Remove the commented-out code from the snippet, keeping the guidance about running indefinitely as a plain comment. - Fail the test when an element is processed before the side input is ready, instead of accepting a None side input value.
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The "Slowly updating global window side inputs" section of the side input patterns page only had a Java sample; the Python block said "No sample present.".
This adds a Python counterpart to the Java sample in snippets.py, references it from the website with code_sample, and covers it with a unit test.
The example uses PeriodicImpulse as a streaming source, re-publishes the external data into the global window on every firing with a repeated trigger and discarding panes, and reads the value with
Latest.Globally().without_defaults(). The without_defaults() variant is required because the default variant adds its own side input, which stops the transform from emitting more than once (#35934).
Addresses #35935
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