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package Algorithm::Backoff::Constant;
use strict;
use warnings;
use parent qw(Algorithm::Backoff);
our $AUTHORITY = 'cpan:PERLANCAR'; # AUTHORITY
our $DATE = '2024-02-24'; # DATE
our $DIST = 'Algorithm-Backoff'; # DIST
our $VERSION = '0.010'; # VERSION
our %SPEC;
$SPEC{new} = {
v => 1.1,
is_class_meth => 1,
is_func => 0,
args => {
%Algorithm::Backoff::attr_consider_actual_delay,
%Algorithm::Backoff::attr_max_actual_duration,
%Algorithm::Backoff::attr_max_attempts,
%Algorithm::Backoff::attr_jitter_factor,
%Algorithm::Backoff::attr_delay_on_success,
%Algorithm::Backoff::attr_min_delay,
%Algorithm::Backoff::attr_max_delay,
delay => {
summary => 'Number of seconds to wait after a failure',
schema => 'ufloat*',
req => 1,
},
},
result_naked => 1,
result => {
schema => 'obj*',
},
};
sub _success {
my ($self, $timestamp) = @_;
$self->{delay_on_success};
}
sub _failure {
my ($self, $timestamp) = @_;
$self->{delay};
}
1;
# ABSTRACT: Backoff using a constant delay
__END__
=pod
=encoding UTF-8
=head1 NAME
Algorithm::Backoff::Constant - Backoff using a constant delay
=head1 VERSION
This document describes version 0.010 of Algorithm::Backoff::Constant (from Perl distribution Algorithm-Backoff), released on 2024-02-24.
=head1 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 L<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
=head1 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".
=head1 METHODS
=head2 new
Usage:
new(%args) -> obj
This function is not exported.
Arguments ('*' denotes required arguments):
=over 4
=item * B<consider_actual_delay> => I<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.
=item * B<delay>* => I<ufloat>
Number of seconds to wait after a failure.
=item * B<delay_on_success> => I<ufloat> (default: 0)
Number of seconds to wait after a success.
=item * B<jitter_factor> => I<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.
=item * B<max_actual_duration> => I<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.
=item * B<max_attempts> => I<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.
=item * B<max_delay> => I<ufloat>
Maximum delay time, in seconds.
=item * B<min_delay> => I<ufloat> (default: 0)
Maximum delay time, in seconds.
=back
Return value: (obj)
=head1 HOMEPAGE
Please visit the project's homepage at L<https://metacpan.org/release/Algorithm-Backoff>.
=head1 SOURCE
Source repository is at L<https://github.com/perlancar/perl-Algorithm-Backoff>.
=head1 SEE ALSO
L<Algorithm::Backoff>
Other C<Algorithm::Backoff::*> classes.
=head1 AUTHOR
perlancar <perlancar@cpan.org>
=head1 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 L<Dist::Zilla>,
L<Dist::Zilla::PluginBundle::Author::PERLANCAR>,
L<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.
=head1 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.
=head1 BUGS
Please report any bugs or feature requests on the bugtracker website L<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.
=cut
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