stu1130 commented on a change in pull request #12572: Make Gluon download
function to be atomic
URL: https://github.com/apache/incubator-mxnet/pull/12572#discussion_r218258922
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File path: python/mxnet/gluon/utils.py
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@@ -242,23 +277,34 @@ def download(url, path=None, overwrite=False,
sha1_hash=None, retries=5, verify_
dirname = os.path.dirname(os.path.abspath(os.path.expanduser(fname)))
if not os.path.exists(dirname):
os.makedirs(dirname)
- while retries+1 > 0:
+ while retries + 1 > 0:
# Disable pyling too broad Exception
# pylint: disable=W0703
try:
- print('Downloading %s from %s...'%(fname, url))
+ print('Downloading {} from {}...'.format(fname, url))
r = requests.get(url, stream=True, verify=verify_ssl)
if r.status_code != 200:
- raise RuntimeError("Failed downloading url %s"%url)
- with open(fname, 'wb') as f:
+ raise RuntimeError('Failed downloading url {}'.format(url))
+ # create uuid for temporary files
+ random_uuid = str(uuid.uuid4())
+ with open('{}.{}'.format(fname, random_uuid), 'wb') as f:
+ # create uuid for temporary files
for chunk in r.iter_content(chunk_size=1024):
if chunk: # filter out keep-alive new chunks
f.write(chunk)
+ # if the target file exists(created by other processes),
+ # delete the temporary file
+ if os.path.exists(fname):
+ os.remove('{}.{}'.format(fname, random_uuid))
Review comment:
Under multiprocessing environment, two processes might pass the check and
one of them finish the download, rename. while the other one is still
downloading or right before rename. In such case, I choose to remove instead of
rename because there is a rare case where rename might be not atomic in windows
based on some research on MSDN. it uses remove to mitigate the risk
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