| Algorithm::Backoff::LILD(3pm) | User Contributed Perl Documentation | Algorithm::Backoff::LILD(3pm) |
NAME¶
Algorithm::Backoff::LILD - Linear Increment, Linear Decrement (LILD) backoff
VERSION¶
This document describes version 0.009 of Algorithm::Backoff::LILD (from Perl distribution Algorithm-Backoff), released on 2019-06-20.
SYNOPSIS¶
use Algorithm::Backoff::LILD;
# 1. instantiate
my $ab = Algorithm::Backoff::LILD->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
min_delay => 1, # optional, default 0
#max_delay => 100, # optional
initial_delay => 3, # required
delay_increment_on_failure => 4, # required
delay_increment_on_success => -5, # required
);
# 2. log success/failure and get a new number of seconds to delay, timestamp is
# optional but must be monotonically increasing.
# for example, using the parameters initial_delay=3,
# delay_increment_on_failure=4, delay_increment_on_success=-5, min_delay=1:
my $secs;
$secs = $ab->failure(); # => 3 (= initial_delay)
$secs = $ab->failure(); # => 7 (3 + 4)
$secs = $ab->failure(); # => 11 (7 + 4)
$secs = $ab->success(); # => 6 (11 - 5)
$secs = $ab->success(); # => 1 (6 - 5)
$secs = $ab->success(); # => 1 (max(1 - 5, 0, min_delay=1))
$secs = $ab->failure(); # => 5 (1 + 4)
Illustration using CLI show-backoff-delays (3 failures followed by 4 successes, followed by 3 failures):
% show-backoff-delays -a LILD --initial-delay 3 --min-delay 1 \
--delay-increment-on-failure 4 --delay-increment-on-success -5 \
0 0 0 1 1 1 1 0 0 0
3
7
11
6
1
1
1
5
9
13
DESCRIPTION¶
Upon failure, this backoff algorithm calculates the next delay as:
D1 = initial_delay D2 = max(min(D1 + delay_increment_on_failure, max_delay), min_delay) ...
Upon success, the next delay is calculated as:
D1 = initial_delay D2 = max(D1 + delay_increment_on_success, min_delay, initial_delay) ...
"initial_delay", "delay_increment_on_failure", and "delay_increment_on_success" are required.
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_increment_on_failure* => float
How much to add to previous delay, in seconds, upon failure (e.g. 5).
- delay_increment_on_success* => float
How much to add to previous delay, in seconds, upon success (e.g. -5).
- initial_delay* => ufloat
Initial delay for the first 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¶
Algorithm::Backoff::LIMD
Algorithm::Backoff::MILD
Algorithm::Backoff::MIMD
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 |