package Algorithm::Backoff::Fibonacci; 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; $SPEC{new} = { v => 1.1, is_class_meth => 1, is_func => 0, args => { %Algorithm::Backoff::attr_consider_actual_delay, %Algorithm::Backoff::attr_max_actual_duration, %Algorithm::Backoff::attr_max_attempts, %Algorithm::Backoff::attr_jitter_factor, %Algorithm::Backoff::attr_delay_on_success, %Algorithm::Backoff::attr_min_delay, %Algorithm::Backoff::attr_max_delay, initial_delay1 => { summary => 'Initial delay for the first attempt after failure, '. 'in seconds', schema => 'ufloat*', req => 1, }, initial_delay2 => { summary => 'Initial delay for the second attempt after failure, '. 'in seconds', schema => 'ufloat*', req => 1, }, }, result_naked => 1, result => { schema => 'obj*', }, }; sub _success { my ($self, $timestamp) = @_; $self->{delay_on_success}; } sub _failure { my ($self, $timestamp) = @_; if ($self->{_attempts} == 1) { $self->{_delay_n_min_1} = 0; $self->{_delay_n} = $self->{initial_delay1}; } elsif ($self->{_attempts} == 2) { $self->{_delay_n_min_1} = $self->{initial_delay1}; $self->{_delay_n} = $self->{initial_delay2}; } else { my $tmp = $self->{_delay_n}; $self->{_delay_n} = $self->{_delay_n_min_1} + $self->{_delay_n}; $self->{_delay_n_min_1} = $tmp; $self->{_delay_n}; } } 1; # ABSTRACT: Backoff using Fibonacci sequence __END__ =pod =encoding UTF-8 =head1 NAME Algorithm::Backoff::Fibonacci - Backoff using Fibonacci sequence =head1 VERSION This document describes version 0.010 of Algorithm::Backoff::Fibonacci (from Perl distribution Algorithm-Backoff), released on 2024-02-24. =head1 SYNOPSIS use Algorithm::Backoff::Fibonacci; # 1. instantiate my $ab = Algorithm::Backoff::Fibonacci->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 => 0.25, # optional, default 0 initial_delay1 => 2, # required initial_delay2 => 3, # required #max_delay => 20, # optional #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; $secs = $ab->failure(); # => 2 (= initial_delay1) $secs = $ab->failure(); # => 3 (= initial_delay2) $secs = $ab->failure(); # => 5 (= 2+3) $secs = $ab->failure(); # => 8 (= 3+5) sleep 1; $secs = $ab->failure(); # => 12 (= 5+8 -1) $secs = $ab->failure(); # => 20 (= min(13+8, 20) = max_delay) $secs = $ab->success(); # => 0 (= delay_on_success) Illustration using CLI L (10 failures followed by 3 successes): % show-backoff-delays -a Fibonacci --initial-delay1 0 --initial-delay2 1 \ 0 0 0 0 0 0 0 0 0 0 1 1 1 0 1 1 2 3 5 8 13 21 34 0 0 0 =head1 DESCRIPTION This backoff algorithm calculates the next delay using Fibonacci sequence. For example, if the two initial numbers are 2 and 3: 2, 3, 5, 8, 13, 21, ... C and C are required. The other attributes are optional. There are limits on the number of attempts (`max_attempts`) and total duration (`max_actual_duration`). It is recommended to add a jitter factor, e.g. 0.25 to add some randomness 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 => I (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 => I (default: 0) Number of seconds to wait after a success. =item * B* => I Initial delay for the first attempt after failure, in seconds. =item * B* => I Initial delay for the second attempt after failure, in seconds. =item * B => I 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 => I (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 => I (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 => I Maximum delay time, in seconds. =item * B => I (default: 0) Maximum delay time, in seconds. =back Return value: (obj) =head1 HOMEPAGE Please visit the project's homepage at L. =head1 SOURCE Source repository is at L. =head1 SEE ALSO L L Other C classes. =head1 AUTHOR perlancar =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, L, L, 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 . 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 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