51 lines
1.4 KiB
Python
51 lines
1.4 KiB
Python
import logging
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from functools import wraps
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logger = logging.getLogger(__name__)
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class FailoverException(Exception):
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""" Exception raised when an operation should be retried by the failover decorator.
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Wraps the exception of the initial failure.
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"""
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def __init__(self, exception):
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super(FailoverException, self).__init__()
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self.exception = exception
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def failover(func):
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""" Wraps a function such that it can be retried on specified failures.
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Raises FailoverException when all failovers are exhausted.
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Example:
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@failover
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def get_google(scheme, use_www=False):
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www = 'www.' if use_www else ''
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try:
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r = requests.get(scheme + '://' + www + 'google.com')
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except requests.RequestException as ex:
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raise FailoverException(ex)
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return r
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def GooglePingTest():
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r = get_google(
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(('http'), {'use_www': False}),
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(('http'), {'use_www': True}),
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(('https'), {'use_www': False}),
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(('https'), {'use_www': True}),
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)
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print('Successfully contacted ' + r.url)
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"""
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@wraps(func)
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def wrapper(*args_sets):
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for arg_set in args_sets:
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try:
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return func(*arg_set[0], **arg_set[1])
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except FailoverException as ex:
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logger.debug('failing over')
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exception = ex.exception
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continue
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raise exception
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return wrapper
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