Crate backoff [−] [src]
ExponentialBackoff
is a backoff implementation that increases the backoff
period for each retry attempt using a randomization function that grows exponentially.
next_backoff
is calculated using the following formula:
randomized interval = retry_interval * (random value in range [1  randomization_factor, 1 + randomization_factor])
In other words next_backoff
will range between the randomization factor
percentage below and above the retry interval.
For example, given the following parameters:
retry_interval = 2 randomization_factor = 0.5 multiplier = 2
the actual backoff period used in the next retry attempt will range between 1 and 3 seconds, multiplied by the exponential, that is, between 2 and 6 seconds.
Note: max_interval
caps the retry_interval
and not the randomized interval.
If the time elapsed since an ExponentialBackoff
instance is created goes past the
max_elapsed_time
, then the method next_backoff
starts returning None
.
The elapsed time can be reset by calling reset
.
Example: Given the following default arguments, for 10 tries the sequence will be,
and assuming we go over the max_elapsed_time
on the 10th try:
Request #  retry_interval (seconds) 
Randomized Interval (seconds) 

1  0.5  [0.25, 0.75] 
2  0.75  [0.375, 1.125] 
3  1.125  [0.562, 1.687] 
4  1.687  [0.8435, 2.53] 
5  2.53  [1.265, 3.795] 
6  3.795  [1.897, 5.692] 
7  5.692  [2.846, 8.538] 
8  8.538  [4.269, 12.807] 
9  12.807  [6.403, 19.210] 
10  19.210  None 
Modules
backoff  
default 
Constants for the exponential backoff policy. 
exponential 
Structs
SystemClock 

Enums
Error 
Error is the error value in an operation's result. 
Traits
Clock 
Clock returns the current time. 
Notify 
Notify is called in 
Operation 
Operation is an operation that can be retried if it fails. 
Type Definitions
ExponentialBackoff 
Exponential backoff policy with system's clock. 