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[py] Fix flaky test_output_buffer_flushes_at_default_size_limit #6585

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Merged
ryzhyk merged 1 commit into from
Jul 3, 2026
Merged

[py] Fix flaky test_output_buffer_flushes_at_default_size_limit #6585

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22 changes: 14 additions & 8 deletions python/tests/runtime/test_output_buffer_size_limit.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@

This test enables output buffering on a Delta Lake sink without setting a time
limit, feeds it more than 10,000,000 records, and verifies that records are
written out: the pipeline's completed-record count advances past the default
written out: the sink's transmitted-record count advances past the default
size cap.
"""

Expand Down Expand Up @@ -95,15 +95,21 @@ def test_output_buffer_flushes_at_default_size_limit(pipeline_name):

pipeline.start()

# The buffer flushes once it crosses the 10M default size cap, pushing
# those records through the Delta sink and advancing the completed count
# past the cap. On timeout the test raises without stopping the pipeline,
# so it is left running on the persistent runtime instance for inspection.
# The buffer flushes once it grows past the 10M default size cap, pushing
# its contents through the Delta sink. Poll the sink's transmitted-record
# count, which the endpoint updates after the Delta commit succeeds.
#
# Do not poll total_completed_records here: a flush triggered by a step
# whose transaction commit is still in progress credits only the
# previous commit boundary; the remaining
# tail never flushes because the default time cap is infinite, so
# the completed count would stay below the cap forever.
wait_for_condition(
"completed-record count advances past the default buffer size cap",
lambda: (
(pipeline.stats().global_metrics.total_completed_records or 0)
"Delta sink transmits at least the default buffer size cap",
lambda: any(
(output.metrics.transmitted_records or 0)
>= _DEFAULT_MAX_OUTPUT_BUFFER_SIZE_RECORDS
for output in pipeline.stats().outputs
),
timeout_s=600.0,
poll_interval_s=2.0,
Expand Down