SO question 55219481: use session windows with Python SDK

gbk_sessions.py

import argparse, json, logging, time

import apache_beam as beam
import apache_beam.transforms.window as window
from apache_beam.io import WriteToText
from apache_beam.options.pipeline_options import PipelineOptions
from apache_beam.options.pipeline_options import SetupOptions


class DebugPrinter(beam.DoFn):
  """Just prints the element with logging"""
  def process(self, element, window=beam.DoFn.WindowParam):
    for x in element[1]:
      logging.info(">>> Received %s %s with window=%s", x['value'], x['timestamp'], window)

    yield element


def run(argv=None):
  parser = argparse.ArgumentParser()
  known_args, pipeline_args = parser.parse_known_args(argv)

  pipeline_options = PipelineOptions(pipeline_args)
  pipeline_options.view_as(SetupOptions).save_main_session = True
  p = beam.Pipeline(options=pipeline_options)

  session_gap = 5 # [s]; 5 seconds
  data = [{'user_id': 'Thanos', 'value': 'event_{}'.format(event), 'timestamp': time.time() + 2**event} for event in range(5)]

  events = (p
    | 'Create Events' >> beam.Create(data) \
    | 'Add Timestamps' >> beam.Map(lambda x: beam.window.TimestampedValue(x, x['timestamp'])) \
    | 'keyed_on_user_id'      >> beam.Map(lambda x: (x['user_id'], x))
    | 'user_session_window'   >> beam.WindowInto(window.Sessions(session_gap),
                                               timestamp_combiner=window.TimestampCombiner.OUTPUT_AT_EOW) \
    | 'Group' >> beam.GroupByKey()
    | 'debug_printer'         >> beam.ParDo(DebugPrinter()))

  result = p.run()
  result.wait_until_finish()

if __name__ == '__main__':
  logging.getLogger().setLevel(logging.INFO)
  run()