shunping opened a new issue, #35384:
URL: https://github.com/apache/beam/issues/35384
### What happened?
When we use sliding windows and groupby, prism seems to fire the windows
earlier than expected (event watermark has not reached window end)
Here is the code to reproduce.
```python
import logging
import apache_beam as beam
from apache_beam.options.pipeline_options import PipelineOptions
from apache_beam.transforms.window import SlidingWindows
from apache_beam.transforms.periodicsequence import PeriodicImpulse
from apache_beam.utils.timestamp import Timestamp
logging.basicConfig(level=logging.INFO)
options = PipelineOptions([
"--streaming",
"--environment_type=LOOPBACK",
"--runner=PrismRunner",
])
WINDOW_SIZE = 5
SLIDE_INTERVAL = 3
now = Timestamp.now()
with beam.Pipeline(options=options) as p:
_ = (
p
| PeriodicImpulse(start_timestamp=now, stop_timestamp=now + 10,
fire_interval=1)
| beam.WithKeys(0)
| beam.WindowInto(SlidingWindows(WINDOW_SIZE, SLIDE_INTERVAL))
| beam.GroupByKey()
| beam.LogElements(level=logging.WARNING, with_timestamp=True,
with_window=True))
```
The output is something like
```
WARNING:root:(0, [1750467252.346215, 1750467253.346215]),
timestamp='2025-06-21T00:54:13.999000Z', window(start=2025-06-21T00:54:09Z,
end=2025-06-21T00:54:14Z)
WARNING:root:(0, [1750467252.346215, 1750467253.346215, 1750467254.346215]),
timestamp='2025-06-21T00:54:16.999000Z', window(start=2025-06-21T00:54:12Z,
end=2025-06-21T00:54:17Z)
WARNING:root:(0, [1750467255.346215, 1750467256.346215]),
timestamp='2025-06-21T00:54:16.999000Z', window(start=2025-06-21T00:54:12Z,
end=2025-06-21T00:54:17Z)
WARNING:root:(0, [1750467255.346215, 1750467256.346215, 1750467257.346215]),
timestamp='2025-06-21T00:54:19.999000Z', window(start=2025-06-21T00:54:15Z,
end=2025-06-21T00:54:20Z)
WARNING:root:(0, [1750467258.346215, 1750467259.346215]),
timestamp='2025-06-21T00:54:19.999000Z', window(start=2025-06-21T00:54:15Z,
end=2025-06-21T00:54:20Z)
WARNING:root:(0, [1750467258.346215, 1750467259.346215, 1750467260.346215,
1750467261.346215]), timestamp='2025-06-21T00:54:22.999000Z',
window(start=2025-06-21T00:54:18Z, end=2025-06-21T00:54:23Z)
WARNING:root:(0, [1750467261.346215]),
timestamp='2025-06-21T00:54:25.999000Z', window(start=2025-06-21T00:54:21Z,
end=2025-06-21T00:54:26Z)
```
Here window(start=2025-06-21T00:54:15Z, end=2025-06-21T00:54:20Z) fires
twice:
- [1750467255.346215, 1750467256.346215, 1750467257.346215]
- [1750467258.346215, 1750467259.346215]
However, the last timestamp of the first firing (i.e. 1750467257 or
2025-06-21T00:54:17) is earlier than the end of the window.
### Issue Priority
Priority: 2 (default / most bugs should be filed as P2)
### Issue Components
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