| Algorithm::Backoff::Fibonacci(3pm) | User Contributed Perl Documentation | Algorithm::Backoff::Fibonacci(3pm) |
NAME¶
Algorithm::Backoff::Fibonacci - Backoff using Fibonacci sequence
VERSION¶
This document describes version 0.009 of Algorithm::Backoff::Fibonacci (from Perl distribution Algorithm-Backoff), released on 2019-06-20.
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 show-backoff-delays (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
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, ...
"initial_delay1" and "initial_delay2" 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".
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_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.
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>.
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.
SEE ALSO¶
<https://en.wikipedia.org/wiki/Fibonacci_number>
Algorithm::Backoff
Other "Algorithm::Backoff::*" classes.
AUTHOR¶
perlancar <perlancar@cpan.org>
COPYRIGHT AND LICENSE¶
This software is copyright (c) 2019 by 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.
| 2022-10-22 | perl v5.34.0 |