Source code for apache_beam.io.restriction_trackers

#
# Licensed to the Apache Software Foundation (ASF) under one or more
# 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
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

"""`iobase.RestrictionTracker` implementations provided with Apache Beam."""
# pytype: skip-file

from __future__ import absolute_import
from __future__ import division

from builtins import object
from typing import Tuple

from apache_beam.io.iobase import RestrictionProgress
from apache_beam.io.iobase import RestrictionTracker
from apache_beam.io.range_trackers import OffsetRangeTracker


[docs]class OffsetRange(object): def __init__(self, start, stop): if start > stop: raise ValueError( 'Start offset must be not be larger than the stop offset. ' 'Received %d and %d respectively.' % (start, stop)) self.start = start self.stop = stop def __eq__(self, other): if not isinstance(other, OffsetRange): return False return self.start == other.start and self.stop == other.stop def __ne__(self, other): # TODO(BEAM-5949): Needed for Python 2 compatibility. return not self == other def __hash__(self): return hash((type(self), self.start, self.stop))
[docs] def split(self, desired_num_offsets_per_split, min_num_offsets_per_split=1): current_split_start = self.start max_split_size = max( desired_num_offsets_per_split, min_num_offsets_per_split) while current_split_start < self.stop: current_split_stop = min(current_split_start + max_split_size, self.stop) remaining = self.stop - current_split_stop # Avoiding a small split at the end. if (remaining < desired_num_offsets_per_split // 4 or remaining < min_num_offsets_per_split): current_split_stop = self.stop yield OffsetRange(current_split_start, current_split_stop) current_split_start = current_split_stop
[docs] def split_at(self, split_pos): # type: (...) -> Tuple[OffsetRange, OffsetRange] return OffsetRange(self.start, split_pos), OffsetRange(split_pos, self.stop)
[docs] def new_tracker(self): return OffsetRangeTracker(self.start, self.stop)
[docs] def size(self): return self.stop - self.start
[docs]class OffsetRestrictionTracker(RestrictionTracker): """An `iobase.RestrictionTracker` implementations for an offset range. Offset range is represented as OffsetRange. """ def __init__(self, offset_range): # type: (OffsetRange) -> None assert isinstance(offset_range, OffsetRange) self._range = offset_range self._current_position = None self._last_claim_attempt = None self._checkpointed = False
[docs] def check_done(self): if self._last_claim_attempt < self._range.stop - 1: raise ValueError( 'OffsetRestrictionTracker is not done since work in range [%s, %s) ' 'has not been claimed.' % ( self._last_claim_attempt if self._last_claim_attempt is not None else self._range.start, self._range.stop))
[docs] def current_restriction(self): return self._range
[docs] def current_progress(self): # type: () -> RestrictionProgress if self._current_position is None: fraction = 0.0 elif self._range.stop == self._range.start: # If self._current_position is not None, we must be done. fraction = 1.0 else: fraction = ( float(self._current_position - self._range.start) / (self._range.stop - self._range.start)) return RestrictionProgress(fraction=fraction)
[docs] def start_position(self): return self._range.start
[docs] def stop_position(self): return self._range.stop
[docs] def try_claim(self, position): if (self._last_claim_attempt is not None and position <= self._last_claim_attempt): raise ValueError( 'Positions claimed should strictly increase. Trying to claim ' 'position %d while last claim attempt was %d.' % (position, self._last_claim_attempt)) self._last_claim_attempt = position if position < self._range.start: raise ValueError( 'Position to be claimed cannot be smaller than the start position ' 'of the range. Tried to claim position %r for the range [%r, %r)' % (position, self._range.start, self._range.stop)) if self._range.start <= position < self._range.stop: self._current_position = position return True return False
[docs] def try_split(self, fraction_of_remainder): if not self._checkpointed: if self._current_position is None: cur = self._range.start - 1 else: cur = self._current_position split_point = ( cur + int(max(1, (self._range.stop - cur) * fraction_of_remainder))) if split_point < self._range.stop: if fraction_of_remainder == 0: self._checkpointed = True self._range, residual_range = self._range.split_at(split_point) return self._range, residual_range