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Algorithm::Backoff::Fibonacci - Backoff using Fibonacci sequence
This document describes version 0.003 of Algorithm::Backoff::Fibonacci (from Perl distribution Algorithm-Backoff), released on 2019-04-10.
use Algorithm::Backoff::Fibonacci; # 1. instantiate my $ar = Algorithm::Backoff::Fibonacci->new( #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 = $ar->failure(); # => 2 (= initial_delay1) $secs = $ar->failure(); # => 3 (= initial_delay2) $secs = $ar->failure(); # => 5 (= 2+3) $secs = $ar->failure(); # => 8 (= 3+5) sleep 1; $secs = $ar->failure(); # => 12 (= 5+8 -1) $secs = $ar->failure(); # => 20 (= min(13+8, 20) = max_delay) $secs = $ar->success(); # => 0 (= delay_on_success)
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, ...
initial_delay2 are required. The other attributes are optional. It is recommended to add a jitter factor, e.g. 0.25 to add some randomness.
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_on_success => ufloat (default: 0)
Number of seconds to wait after a success.
initial_delay1* => ufloat
Initial delay for the first attempt after failure, in seconds.
initial_delay2* => ufloat
Initial delay for the second attempt after failure, in seconds.
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.
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.
Return value: (obj)
Please visit the project's homepage at https://metacpan.org/release/Algorithm-Backoff.
Source repository is at https://github.com/perlancar/perl-Algorithm-Backoff.
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.
This software is copyright (c) 2019 by firstname.lastname@example.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.