[Failing Test]: Flake in apache_beam.io.textio_test.TextSinkTest testMethod=test_write_pipeline_footer

[tvalentyn]

What happened?

From https://github.com/apache/beam/actions/runs/31025803388/job/92373814485?pr=39595:

2026-08-05T17:14:42.0618351Z ___________________ TextSinkTest.test_write_pipeline_footer ____________________
2026-08-05T17:14:42.0620672Z [gw0] linux -- Python 3.10.20 /runner/_work/beam/beam/sdks/python/test-suites/tox/py310/build/srcs/sdks/python/target/.tox-py310/py310/bin/python
2026-08-05T17:14:42.0621937Z 
2026-08-05T17:14:42.0622606Z self = <apache_beam.io.textio_test.TextSinkTest testMethod=test_write_pipeline_footer>
2026-08-05T17:14:42.0623462Z 
2026-08-05T17:14:42.0623839Z     def test_write_pipeline_footer(self):
2026-08-05T17:14:42.0625081Z       with TestPipeline() as pipeline:
2026-08-05T17:14:42.0625881Z         footer_text = 'footer'
2026-08-05T17:14:42.0626872Z         pcoll = pipeline | beam.core.Create(self.lines)
2026-08-05T17:14:42.0627826Z         pcoll | 'Write' >> WriteToText(   # pylint: disable=expression-not-assigned
2026-08-05T17:14:42.0628703Z           self.path,
2026-08-05T17:14:42.0629309Z           footer=footer_text)
2026-08-05T17:14:42.0629939Z     
2026-08-05T17:14:42.0630447Z       read_result = []
2026-08-05T17:14:42.0631106Z       for file_name in glob.glob(self.path + '*'):
2026-08-05T17:14:42.0631857Z         with open(file_name, 'rb') as f:
2026-08-05T17:14:42.0632543Z           read_result.extend(f.read().splitlines())
2026-08-05T17:14:42.0633260Z     
2026-08-05T17:14:42.0633976Z >     self.assertEqual(sorted(read_result[:-1]), sorted(self.lines))
2026-08-05T17:14:42.0635575Z E     AssertionError: Lists differ: [b'Li[1166 chars]ne 98', b'Line 99', b'footer', b'footer', b'footer', b'footer'] != [b'Li[1166 chars]ne 98', b'Line 99']
2026-08-05T17:14:42.0636883Z E     
2026-08-05T17:14:42.0637646Z E     First list contains 4 additional elements.
2026-08-05T17:14:42.0638599Z E     First extra element 100:
2026-08-05T17:14:42.0639208Z E     b'footer'
2026-08-05T17:14:42.0639602Z E     
2026-08-05T17:14:42.0640173Z E     Diff is 1593 characters long. Set self.maxDiff to None to see it.
2026-08-05T17:14:42.0640702Z 
2026-08-05T17:14:42.0640993Z apache_beam/io/textio_test.py:1689: AssertionError

Issue Failure

Failure: Test is flaky

Issue Priority

Priority: 1 (unhealthy code / failing or flaky postcommit so we cannot be sure the product is healthy)

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