BackOff

Back-off algorithm implementation.

Installation

You can install the latest version via Composer:

composer require orangesoft/backoff

This package requires PHP 8.1 or later.

Quick usage

Configure Orangesoft\BackOff\Retry\Retry::class, any of back-off classes, and Orangesoft\BackOff\Retry\ExceptionClassifier\ExceptionClassifier::class to retry a business logic when an exception is thrown:

<?php

use Orangesoft\BackOff\ExponentialBackOff;
use Orangesoft\BackOff\Duration\Microseconds;
use Orangesoft\BackOff\Retry\ExceptionClassifier\ExceptionClassifier;
use Orangesoft\BackOff\Retry\Retry;

$retry = new Retry(
    maxAttempts: 3,
    backOff: new ExponentialBackOff(
        baseTime: new Microseconds(1_000),
        capTime: new Microseconds(512_000),
        factor: 2.0,
    ),
    exceptionClassifier: new ExceptionClassifier(
        classNames: [
            \RuntimeException::class,
        ],
    ),
);

Use the Orangesoft\BackOff\Retry\Retry::call(callable $callback): mixed method to wrap the business logic and call it with retry functionality:

/** @var int $result */
$result = $retry->call(static function (): int {
    $random = mt_rand(0, 1);
    
    if (0 === $random % 2) {
        throw new \RuntimeException();
    }
    
    return $random;
});

The following back-off strategies are available:

• Orangesoft\BackOff\CallbackBackOff
• Orangesoft\BackOff\ConstantBackOff
• Orangesoft\BackOff\DecorrelatedJitterBackOff
• Orangesoft\BackOff\ExponentialBackOff
• Orangesoft\BackOff\FibonacciBackOff
• Orangesoft\BackOff\LinearBackOff

Enable Jitter

Pass the implementation of Orangesoft\BackOff\Jitter\JitterInterface::class to the back-off class and jitter will be enabled:

<?php

use Orangesoft\BackOff\ExponentialBackOff;
use Orangesoft\BackOff\Duration\Microseconds;
use Orangesoft\BackOff\Jitter\EqualJitter;

$backOff = new ExponentialBackOff(
    baseTime: new Microseconds(1_000),
    capTime: new Microseconds(512_000),
    factor: 2.0,
    jitter: new EqualJitter(),
);

for ($i = 1; $i <= 10; $i++) {
    $backOff->backOff(
        attempt: $i,
    );
}

Below you can see the time intervals in microseconds for exponential back-off with a factor of 2.0 and equal jitter, where the base time is 1_000 μs and the cap time is 512_000 μs:

+---------+---------------------------+--------------------+
| attempt | exponential back-off (μs) | equal jitter (μs)  |
+---------+---------------------------+--------------------+
|       1 |                     1_000 |         [0, 1_000] |
|       2 |                     2_000 |     [1_000, 2_000] |
|       3 |                     4_000 |     [2_000, 4_000] |
|       4 |                     8_000 |     [4_000, 8_000] |
|       5 |                    16_000 |    [8_000, 16_000] |
|       6 |                    32_000 |   [16_000, 32_000] |
|       7 |                    64_000 |   [32_000, 64_000] |
|       8 |                   128_000 |  [64_000, 128_000] |
|       9 |                   256_000 | [128_000, 256_000] |
|      10 |                   512_000 | [256_000, 512_000] |
+---------+---------------------------+--------------------+

The following jitters are available:

• Orangesoft\BackOff\Jitter\EqualJitter
• Orangesoft\BackOff\Jitter\FullJitter
• Orangesoft\BackOff\Jitter\ScatteredJitter

Read more about Back-Off and Jitter on AWS Architecture Blog.