Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/google/auth/_exponential_backoff.py: 44%

1# Copyright 2022 Google LLC 

2# 

3# Licensed under the Apache License, Version 2.0 (the "License"); 

4# you may not use this file except in compliance with the License. 

5# You may obtain a copy of the License at 

6# 

7# http://www.apache.org/licenses/LICENSE-2.0 

8# 

9# Unless required by applicable law or agreed to in writing, software 

10# distributed under the License is distributed on an "AS IS" BASIS, 

11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 

12# See the License for the specific language governing permissions and 

13# limitations under the License. 

14 

15import random 

16import time 

17 

18import six 

19 

20# The default amount of retry attempts 

21_DEFAULT_RETRY_TOTAL_ATTEMPTS = 3 

22 

23# The default initial backoff period (1.0 second). 

24_DEFAULT_INITIAL_INTERVAL_SECONDS = 1.0 

25 

26# The default randomization factor (0.1 which results in a random period ranging 

27# between 10% below and 10% above the retry interval). 

28_DEFAULT_RANDOMIZATION_FACTOR = 0.1 

29 

30# The default multiplier value (2 which is 100% increase per back off). 

31_DEFAULT_MULTIPLIER = 2.0 

32 

33"""Exponential Backoff Utility 

34 

35This is a private module that implements the exponential back off algorithm. 

36It can be used as a utility for code that needs to retry on failure, for example 

37an HTTP request. 

38""" 

39 

40 

41class ExponentialBackoff(six.Iterator): 

42 """An exponential backoff iterator. This can be used in a for loop to 

43 perform requests with exponential backoff. 

44 

45 Args: 

46 total_attempts Optional[int]: 

47 The maximum amount of retries that should happen. 

48 The default value is 3 attempts. 

49 initial_wait_seconds Optional[int]: 

50 The amount of time to sleep in the first backoff. This parameter 

51 should be in seconds. 

52 The default value is 1 second. 

53 randomization_factor Optional[float]: 

54 The amount of jitter that should be in each backoff. For example, 

55 a value of 0.1 will introduce a jitter range of 10% to the 

56 current backoff period. 

57 The default value is 0.1. 

58 multiplier Optional[float]: 

59 The backoff multipler. This adjusts how much each backoff will 

60 increase. For example a value of 2.0 leads to a 200% backoff 

61 on each attempt. If the initial_wait is 1.0 it would look like 

62 this sequence [1.0, 2.0, 4.0, 8.0]. 

63 The default value is 2.0. 

64 """ 

65 

66 def __init__( 

67 self, 

68 total_attempts=_DEFAULT_RETRY_TOTAL_ATTEMPTS, 

69 initial_wait_seconds=_DEFAULT_INITIAL_INTERVAL_SECONDS, 

70 randomization_factor=_DEFAULT_RANDOMIZATION_FACTOR, 

71 multiplier=_DEFAULT_MULTIPLIER, 

72 ): 

73 self._total_attempts = total_attempts 

74 self._initial_wait_seconds = initial_wait_seconds 

75 

76 self._current_wait_in_seconds = self._initial_wait_seconds 

77 

78 self._randomization_factor = randomization_factor 

79 self._multiplier = multiplier 

80 self._backoff_count = 0 

81 

82 def __iter__(self): 

83 self._backoff_count = 0 

84 self._current_wait_in_seconds = self._initial_wait_seconds 

85 return self 

86 

87 def __next__(self): 

88 if self._backoff_count >= self._total_attempts: 

89 raise StopIteration 

90 self._backoff_count += 1 

91 

92 jitter_variance = self._current_wait_in_seconds * self._randomization_factor 

93 jitter = random.uniform( 

94 self._current_wait_in_seconds - jitter_variance, 

95 self._current_wait_in_seconds + jitter_variance, 

96 ) 

97 

98 time.sleep(jitter) 

99 

100 self._current_wait_in_seconds *= self._multiplier 

101 return self._backoff_count 

102 

103 @property 

104 def total_attempts(self): 

105 """The total amount of backoff attempts that will be made.""" 

106 return self._total_attempts 

107 

108 @property 

109 def backoff_count(self): 

110 """The current amount of backoff attempts that have been made.""" 

111 return self._backoff_count