NAME

Algorithm::Backoff - Various backoff strategies for retry

VERSION

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

SYNOPSIS

 # 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

DESCRIPTION

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.

METHODS

new

Usage:

 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)

success

Usage:

 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.

failure

Usage:

 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).

HOMEPAGE

Please visit the project's homepage at <https://metacpan.org/release/Algorithm-Backoff>.

SOURCE

Source repository is at <https://github.com/perlancar/perl-Algorithm-Backoff>.

BUGS

Please report any bugs or feature requests on the bugtracker website <https://rt.cpan.org/Public/Dist/Display.html?Name=Algorithm-Backoff>

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.

AUTHOR

perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

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