sdks/python/apache_beam/io/sources_test.py

#
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# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
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"""Unit tests for the sources framework."""
# pytype: skip-file

import logging
import os
import tempfile
import unittest

import apache_beam as beam
from apache_beam import coders
from apache_beam.io import iobase
from apache_beam.io import range_trackers
from apache_beam.testing.test_pipeline import TestPipeline
from apache_beam.testing.util import assert_that
from apache_beam.testing.util import equal_to


class LineSource(iobase.BoundedSource):
  """A simple source that reads lines from a given file."""

  TEST_BUNDLE_SIZE = 10

  def __init__(self, file_name):
    self._file_name = file_name

  def read(self, range_tracker):
    with open(self._file_name, 'rb') as f:
      start = range_tracker.start_position()
      f.seek(start)
      if start > 0:
        f.seek(-1, os.SEEK_CUR)
        start -= 1
        start += len(f.readline())
      current = start
      line = f.readline()
      while range_tracker.try_claim(current):
        if not line:
          return
        yield line.rstrip(b'\n')
        current += len(line)
        line = f.readline()

  def split(self, desired_bundle_size, start_position=None, stop_position=None):
    assert start_position is None
    assert stop_position is None
    size = self.estimate_size()

    bundle_start = 0
    while bundle_start < size:
      bundle_stop = min(bundle_start + LineSource.TEST_BUNDLE_SIZE, size)
      yield iobase.SourceBundle(
          bundle_stop - bundle_start, self, bundle_start, bundle_stop)
      bundle_start = bundle_stop

  def get_range_tracker(self, start_position, stop_position):
    if start_position is None:
      start_position = 0
    if stop_position is None:
      stop_position = self._get_file_size()
    return range_trackers.OffsetRangeTracker(start_position, stop_position)

  def default_output_coder(self):
    return coders.BytesCoder()

  def estimate_size(self):
    return self._get_file_size()

  def _get_file_size(self):
    with open(self._file_name, 'rb') as f:
      f.seek(0, os.SEEK_END)
      return f.tell()


class SourcesTest(unittest.TestCase):
  def _create_temp_file(self, contents):
    with tempfile.NamedTemporaryFile(delete=False) as f:
      f.write(contents)
      return f.name

  def test_read_from_source(self):
    file_name = self._create_temp_file(b'aaaa\nbbbb\ncccc\ndddd')

    source = LineSource(file_name)
    range_tracker = source.get_range_tracker(None, None)
    result = [line for line in source.read(range_tracker)]

    self.assertCountEqual([b'aaaa', b'bbbb', b'cccc', b'dddd'], result)
    self.assertTrue(
        range_tracker.last_attempted_record_start >=
        range_tracker.stop_position())

  def test_source_estimated_size(self):
    file_name = self._create_temp_file(b'aaaa\n')

    source = LineSource(file_name)
    self.assertEqual(5, source.estimate_size())

  def test_run_direct(self):
    file_name = self._create_temp_file(b'aaaa\nbbbb\ncccc\ndddd')
    with TestPipeline() as pipeline:
      pcoll = pipeline | beam.io.Read(LineSource(file_name))
      assert_that(pcoll, equal_to([b'aaaa', b'bbbb', b'cccc', b'dddd']))


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