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#! /usr/bin/env python
# -*- coding: utf-8 -*-
# COPYRIGHT NOTICE STARTS HERE
# Copyright 2019 © Samsung Electronics Co., Ltd.
#
# Licensed 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.
# COPYRIGHT NOTICE ENDS HERE
import concurrent.futures
import logging
from abc import ABC, abstractmethod
from downloader import AbstractDownloader
log = logging.getLogger(__name__)
class ConcurrentDownloader(AbstractDownloader, ABC):
def __init__(self, list_type, *list_args, workers=None):
super().__init__(list_type, *list_args)
self._workers = workers
@abstractmethod
def _download_item(self, item):
"""
Download item from list
:param item: item to be downloaded
"""
pass
def download(self):
"""
Download images concurrently from data lists.
"""
if not self._initial_log():
return
items_left = len(self._missing)
try:
for _ in self.run_concurrent(self._download_item, self._missing.items()):
items_left -= 1
log.info('{} {} left to download.'.format(items_left, self._list_type))
except RuntimeError as err:
log.error('{} {} were not downloaded.'.format(items_left, self._list_type))
raise err
def run_concurrent(self, fn, iterable, *args):
"""
Run function concurrently for iterable
:param fn: function to run
:param iterable: iterable to process
:param args: arguments for function (fn)
"""
with concurrent.futures.ThreadPoolExecutor(max_workers=self._workers) as executor:
futures = [executor.submit(fn, item, *args) for item in iterable]
error_occurred = False
for future in concurrent.futures.as_completed(futures):
error = future.exception()
if error:
error_occurred = True
else:
yield
if error_occurred:
raise RuntimeError('One or more errors occurred')
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