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�~�e� � � � d dl Z G d� d� Zy)� Nc �0 � e Zd ZdZd� Zd� Zd� Zd� Zdd�Zy) �ExponentialBackoffz^
Keeps track of a backoff delay that staggers down and staggers up
exponentially.
c �. � d| _ || _ || _ y )Nr )� _error_count� _start_delay�
_max_delay)�self� start_delay� max_delays �7/usr/lib/python3/dist-packages/landscape/lib/backoff.py�__init__zExponentialBackoff.__init__
s � � ��� '���#��� c �d � | xj dz c_ t | j d� | _ y)z0Decreases error count with zero being the lowest� r N)r �max�r s r �decreasezExponentialBackoff.decrease s( � � ���Q� �� �� 1� 1�1� 5��r c �j � | j � | j k r| xj dz
c_ yy)z=Increases error count but not higher than gives the max delayr N)� get_delayr r r s r �increasezExponentialBackoff.increase s+ � � �>�>� �d�o�o� -� � � �� "� � .r c � � | j r d| j dz
z | j z }nd}t t |� | j � S )aR
Calculates the delay using formula that gives this chart. In this
specific example start is 5 seconds and max is 60 seconds
Count Delay
0 0
1 5
2 10
3 20
4 40
5 60 (max)
� r r )r r �min�intr )r �delays r r z ExponentialBackoff.get_delay sG � � � � ��4�,�,�q�0�1�T�5F�5F�F�E��E��3�u�:�t���/�/r c � � | j � }|d|z
z }||z t j � z }t ||z � S )z�
Adds randomness to the specified stagger of the delay. For example
for a delay of 12 and 25% stagger, it works out to 9 + rand(0,3)
r )r �randomr )r �stagger_fractionr �non_random_part� random_parts r �get_random_delayz#ExponentialBackoff.get_random_delay- sF � �
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__module__� __qualname__�__doc__r
r r r r! � r r r r s � ��
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0�$2r r )r r r& r r �<module>r' s ��
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