learning/katas/python/Streaming/Triggers/Event Time Triggers/task.py

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# beam-playground:
#   name: EventTimeTriggers
#   description: Task from katas to count events with event time triggers
#   multifile: true
#   files:
#     - name: generate_event.py
#   context_line: 54
#   categories:
#     - Streaming
#   complexity: MEDIUM
#   tags:
#     - windowing
#     - triggers
#     - count
#     - event

import apache_beam as beam
from generate_event import GenerateEvent
from apache_beam.transforms.window import FixedWindows
from apache_beam.transforms.trigger import AccumulationMode
from apache_beam.transforms.trigger import AfterWatermark
from apache_beam.utils.timestamp import Duration
from apache_beam.transforms.util import LogElements


class CountEvents(beam.PTransform):
  def expand(self, events):
    return (events
            | beam.WindowInto(FixedWindows(5),
                              trigger=AfterWatermark(),
                              accumulation_mode=AccumulationMode.DISCARDING,
                              allowed_lateness=Duration(seconds=0))
            | beam.CombineGlobally(beam.combiners.CountCombineFn()).without_defaults())

with beam.Pipeline() as p:
  (p | GenerateEvent.sample_data()
     | CountEvents()
     | LogElements(with_window=True))