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Add a retry when downloading a file

When downloading of new file fails due to short and temporary network
issue then wait a few seconds and retry to download the file again.

There were situations when small network issues caused python-tempestconf
to end with an error.

Story: 2006231
Task: 35832

Change-Id: Ie3f1d8b412dccecac2b05f6b5f540e36824777a4
changes/07/672507/5
Lukas Piwowarski 3 years ago
parent
commit
041dac5acb
  1. 53
      config_tempest/services/image.py
  2. 7
      releasenotes/notes/Add-retry-when-downloading-file-1ba9f2b03b6ef258.yaml

53
config_tempest/services/image.py

@ -13,9 +13,11 @@
# License for the specific language governing permissions and limitations
# under the License.
from functools import wraps
import os
import shutil
import subprocess
import time
from six.moves import urllib
from tempest.lib import exceptions
@ -222,6 +224,55 @@ class ImageService(VersionedService):
with open(path, 'wb') as out:
out.write(body.data)
def retry(ExceptionToCheck, tries=4, delay=3, backoff=2, logger=None):
"""Retry calling the decorated function using exponential backoff
http://www.saltycrane.com/blog/2009/11/trying-out-retry-decorator-python/
original from: http://wiki.python.org/moin/PythonDecoratorLibrary#Retry
Licensed under the BSD 3-Clause "New" or "Revised" License
(https://github.com/saltycrane/retry-decorator/blob/master/LICENSE)
:param ExceptionToCheck: the exception to check
:type ExceptionToCheck: Exception or tuple
:param tries: number of times before giving up
:type type: int
:param delay: initial delay between retries in seconds
:type type: int
:param backoff: backoff multiplier e.g. value of 2 will double the
delay each retry
:type backoff: int
:param logger: logger to use. If None, print
:type logger: logging. Logger instance
"""
def deco_retry(f):
@wraps(f)
def f_retry(*args, **kwargs):
mtries, mdelay = tries, delay
while mtries > 1:
try:
return f(*args, **kwargs)
except ExceptionToCheck as e:
msg = "%s, Retrying in %d seconds." % (str(e), mdelay)
if logger:
logger.warning(msg)
else:
print(msg)
time.sleep(mdelay)
mtries -= 1
mdelay *= backoff
return f(*args, **kwargs)
return f_retry
return deco_retry
@retry(urllib.error.URLError, logger=C.LOG)
def retry_urlopen(self, url):
"""Opens url using urlopen. If it fails, it will try again.
:type url: string
"""
return urllib.request.urlopen(url)
def _download_file(self, url, destination):
"""Downloads a file specified by `url` to `destination`.
@ -232,7 +283,7 @@ class ImageService(VersionedService):
C.LOG.info("Image '%s' already fetched to '%s'.", url, destination)
return
C.LOG.info("Downloading '%s' and saving as '%s'", url, destination)
f = urllib.request.urlopen(url)
f = self.retry_urlopen(url)
data = f.read()
with open(destination, "wb") as dest:
dest.write(data)

7
releasenotes/notes/Add-retry-when-downloading-file-1ba9f2b03b6ef258.yaml

@ -0,0 +1,7 @@
---
features:
- |
When downloading of new file fails due to short and temporary
network issue then python-tempestconf does not end immediately
with an error but rather waits a few seconds and retries to
download the file again.
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