oracular (3) Algorithm::Backoff::Constant.3pm.gz
NAME
Algorithm::Backoff::Constant - Backoff using a constant delay
VERSION
This document describes version 0.010 of Algorithm::Backoff::Constant (from Perl distribution Algorithm-
Backoff), released on 2024-02-24.
SYNOPSIS
use Algorithm::Backoff::Constant;
# 1. instantiate
my $ab = Algorithm::Backoff::Constant->new(
#consider_actual_delay => 1, # optional, default 0
#max_actual_duration => 0, # optional, default 0 (retry endlessly)
#max_attempts => 0, # optional, default 0 (retry endlessly)
#jitter_factor => 0, # optional, set to positive value to add randomness
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 argument (default is current time) but must be monotonically
# increasing.
my $secs = $ab->failure(1554652553); # => 2
my $secs = $ab->success(); # => 0
my $secs = $ab->failure(); # => 2
Illustration using CLI show-backoff-delays (5 failures followed by 3 successes):
% show-backoff-delays -a Constant --delay 2 \
0 0 0 0 0 1 1 1
2
2
2
2
2
0
0
0
DESCRIPTION
This backoff strategy is one of the simplest: it waits X second(s) after each failure, or Y second(s)
(default 0) after a success. There are limits on the number of attempts (`max_attempts`) and total
duration (`max_actual_duration`). Some randomness can be introduced to avoid "thundering herd problem".
METHODS
new
Usage:
new(%args) -> obj
This function is not exported.
Arguments ('*' denotes required arguments):
• consider_actual_delay => bool (default: 0)
Whether to consider actual delay.
If set to true, will take into account the actual delay (timestamp difference). For example, when
using the Constant strategy of delay=2, you log failure() again right after the previous failure()
(i.e. specify the same timestamp). failure() will then return ~2+2 = 4 seconds. On the other hand,
if you waited 2 seconds before calling failure() again (i.e. specify the timestamp that is 2 seconds
larger than the previous timestamp), failure() will return 2 seconds. And if you waited 4 seconds or
more, failure() will return 0.
• delay* => ufloat
Number of seconds to wait after a failure.
• delay_on_success => ufloat (default: 0)
Number of seconds to wait after a success.
• 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_actual_duration => ufloat (default: 0)
Maximum number of seconds for all of the attempts (0 means unlimited).
If set to a positive number, will limit the number of seconds for all of the attempts. This setting
is used to limit the amount of time you are willing to spend on a task. For example, when using the
Exponential strategy of initial_delay=3 and max_attempts=10, the delays will be 3, 6, 12, 24, ... If
failures are logged according to the suggested delays, and max_actual_duration is set to 21 seconds,
then the third failure() will return -1 instead of 24 because 3+6+12 >= 21, even though max_attempts
has not been exceeded.
• 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.
• max_delay => ufloat
Maximum delay time, in seconds.
• min_delay => ufloat (default: 0)
Maximum delay time, in seconds.
Return value: (obj)
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>.
SEE ALSO
Algorithm::Backoff
Other "Algorithm::Backoff::*" classes.
AUTHOR
perlancar <perlancar@cpan.org>
CONTRIBUTING
To contribute, you can send patches by email/via RT, or send pull requests on GitHub.
Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then
test via:
% prove -l
If you want to build the distribution (e.g. to try to install it locally on your system), you can install
Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, Pod::Weaver::PluginBundle::Author::PERLANCAR,
and sometimes one or two other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps required
beyond that are considered a bug and can be reported to me.
COPYRIGHT AND LICENSE
This software is copyright (c) 2024, 2019 by perlancar <perlancar@cpan.org>. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
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.