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@anentropic
Last active August 29, 2015 14:18
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retry context manager
import time
from logging import getLogger
class RetryContextInvalidResult(Exception):
pass
class RetryContext(object):
"""
Usage:
with retry_request(max_retries=3, delay=0.1) as manager:
response = manager.execute(requests.get, 'http://google.com')
"""
def __init__(self, max_retries, validator=lambda r: True, delay=None):
self.max_retries = max_retries
self.validator = validator
self.delay = delay
self.logger = getLogger('utils.requests.RetryContext')
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, traceback):
return False
def execute(self, method, *args, **kwargs):
error = None
for _ in range(self.max_retries):
try:
result = method(*args, **kwargs)
except Exception as error:
self.logger.warning(error.message)
else:
if self.validator(result):
return result
error = RetryContextInvalidResult(
'Invalid result from <{method_module}.{method_name}'
' args={args}, kwargs={kwargs}> ...failed validator:'
' {validator_module}.{validator_name}'.format(
method_module=method.__module__,
method_name=method.__name__,
args=args,
kwargs=kwargs,
validator_module=self.validator.__module__,
validator_name=self.validator.__name__,
)
)
# if we run out of retries the exception will be re-raised,
# so don't confuse the logs with an ERROR message here:
self.logger.warning(error.message)
if self.delay:
time.sleep(self.delay)
raise error
def retry_request(max_retries, delay=1):
'''
We want to retry in the case of transient http connection error, i.e.
where no response would be returned.
In case of successful response, http error statuses should be handled
in your own code.
'''
return RetryContext(
max_retries=max_retries,
delay=delay,
)
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