Cerberus

Introduction

This is a Circuit Breaker pattern implementation in PHP.

This library helps you to handle external services timeouts and outages.

Requirements

• PHP >= 7.2
• Any cache library implementing psr/simple-cache

Installation

composer require los/cerberus:^1.0

Configuration

You can manually create a Cerberus instance or use a Factory

Factory

'factories' => [
    Los\Cerberus\Cerberus::class => Los\Cerberus\CerberusFactory::class
],

and copy the configuration file config/cerberus.global.php.dist to your config/autoload/cerberus.global.php and change to your needs.

return [
    'cerberus' => [
        'max_failures' => 5,
        'timeout' => 60,
    ]
];

The maxFailure parameter is the number of failures after which the circuit is opened and the service becomes not available.

When the timeout is reached, the circuit becomes half opened and one attempt is possible and the status is updated.

The factory pull the cache from the container using

$container->get(\Psr\SimpleCache\CacheInterface::class)

so you need to have one implemented.

Manually

You can create a Cerberus instance manually:

$storage = new Cache(); // Any psr/simple-cache implementation
$cerberus = new Cerberus($storage, 5, 60);

Usage

The usage is simple. Each time you will access a remote resource (like an Web Service), check for its availability and report its success or failure:

if ($cerberus->isAvailable()) {
    try {
        $http->makeRequest();
        $cerberus->reportSuccess();
    } catch (\Exception $ex) {
        $cerberus->reportFailure();
    }
}

You can use Cerberus to control more than one service. In this scenario, use the methods passing a service name:

if ($cerberus->isAvailable('service-one')) {
    try {
        $http->makeRequest();
        $cerberus->reportSuccess('service-one');
    } catch (\Exception $ex) {
        $cerberus->reportFailure('service-one');
    }
}
if ($cerberus->isAvailable('service-two')) {
    try {
        $http->makeRequest();
        $cerberus->reportSuccess('service-two');
    } catch (\Exception $ex) {
        $cerberus->reportFailure('service-two');
    }
}