Algorithm::Backoff - Various backoff strategies for retry


This document describes version 0.009 of Algorithm::Backoff (from Perl distribution Algorithm-Backoff), released on 2019-06-20.


 # 1. pick a strategy and instantiate

 use Algorithm::Backoff::Constant;
 my $ab = Algorithm::Backoff::Constant->new(
     delay             => 2, # required
     #delay_on_success => 0, # optional, default 0

 # 2. log success/failure and get a new number of seconds to delay, timestamp is
 # optional but must be monotonically increasing.

 my $secs = $ab->failure(); # => 2
 my $secs = $ab->success(); # => 0
 my $secs = $ab->failure(); # => 2


This distribution provides several classes that implement various backoff strategies for setting delay between retry attempts.

This class (Algorithm::Backoff) is a base class only.




 new(%args) -> obj

This function is not exported.

Arguments ('*' denotes required arguments):

  • jitter_factor => float

    How much to add randomness.

    If you set this to a value larger than 0, the actual delay will be between a random number between original_delay * (1-jitter_factor) and original_delay * (1+jitter_factor). Jitters are usually added to avoid so-called "thundering herd" problem.

    The jitter will be applied to delay on failure as well as on success.

  • max_attempts => uint (default: 0)

    Maximum number consecutive failures before giving up.

    0 means to retry endlessly without ever giving up. 1 means to give up after a single failure (i.e. no retry attempts). 2 means to retry once after a failure. Note that after a success, the number of attempts is reset (as expected). So if max_attempts is 3, and if you fail twice then succeed, then on the next failure the algorithm will retry again for a maximum of 3 times.

Return value: (obj)



 my $secs = $obj->success([ $timestamp ]);

Log a successful attempt. If not specified, $timestamp defaults to current time. Will return the suggested number of seconds to wait before doing another attempt.



 my $secs = $obj->failure([ $timestamp ]);

Log a failed attempt. If not specified, $timestamp defaults to current time. Will return the suggested number of seconds to wait before doing another attempt, or -1 if it suggests that one gives up (e.g. if max_attempts parameter has been exceeded).


Please visit the project's homepage at


Source repository is at


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.


Retry::Backoff - an application of Algorithm::Backoff to retry a piece of code using various backoff strategies.

App::AlgorithmBackoffUtils - various CLI's related to Algorithm::Backoff.

Action::Retry - Somehow I didn't find this module before writing Algorithm::Backoff. Otherwise I probably would not have created Algorithm::Backoff. But Algorithm::Backoff offers an alternative interface, some additional parameters (like delay on success and jitter factor), a lighter footprint (no Moo), and a couple more strategies.


perlancar <>


This software is copyright (c) 2019 by

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.