PHP Circuit Breaker

Resiliency pattern for PHP microservices. This library implements a circuit breaker using Redis for state tracking. It protects your services from cascading failures by stopping calls to unhealthy dependencies and gradually allowing traffic as they recover.

Learn more about circuit breakers: https://martinfowler.com/bliki/CircuitBreaker.html

Features

• Simple API: canPass, succeed, failed
• Redis-backed state with configurable windows/timeouts
• Pluggable alert hook to notify when circuits open
• PHP 8.1+ native enum for states in v2

Versions

• 2.x (current): PHP 8.1+, native enums, PHPUnit 10, GitHub Actions
• 1.x (legacy): PHP 7.4+/8.0+, uses eloquent/enumeration and Travis CI

See CHANGELOG for details and migration notes.

Requirements

• PHP 8.1+
• Redis server
• ext-redis PHP extension

Install

• v2 (recommended): composer require gabrielanhaia/php-circuit-breaker:^2.0
• v1 (legacy): composer require gabrielanhaia/php-circuit-breaker:^1.0

Quick Start

use GabrielAnhaia\PhpCircuitBreaker\Adapter\Redis\RedisCircuitBreaker;
use GabrielAnhaia\PhpCircuitBreaker\CircuitBreaker;

$settings = [
    'exceptions_on' => false,
    'time_window' => 20,
    'time_out_open' => 30,
    'time_out_half_open' => 20,
    'total_failures' => 5,
];

$redis = new \Redis();
$redis->connect('127.0.0.1', 6379);

$driver = new RedisCircuitBreaker($redis);
$cb = new CircuitBreaker($driver, $settings);

$service = 'PAYMENTS_API';
if (!$cb->canPass($service)) {
    // Short-circuit
    return;
}

try {
    // Call dependency...
    $cb->succeed($service);
} catch (\Throwable $e) {
    $cb->failed($service);
}

Configuration

• exceptions_on (bool): throw when circuit is open (default: false)
• time_window (int): seconds to track failures (default: 20)
• time_out_open (int): seconds to keep circuit open (default: 30)
• time_out_half_open (int): additional seconds before half-open closes (default: 20)
• total_failures (int): failures within window to open (default: 5)

Circuit State

In v2+, states are represented with a native enum: GabrielAnhaia\PhpCircuitBreaker\CircuitStateEnum with cases OPEN, CLOSED, HALF_OPEN. You don’t normally need to consume this directly unless you’re writing custom adapters.

Alerts

Implement GabrielAnhaia\PhpCircuitBreaker\Contract\Alert and pass it to CircuitBreaker to receive callbacks when a circuit opens.

use GabrielAnhaia\PhpCircuitBreaker\Contract\Alert;

class LoggerAlert implements Alert {
    public function emmitOpenCircuit(string $serviceName)
    {
        error_log("Circuit opened: {$serviceName}");
    }
}

Redis Keys

Keys are namespaced per service:

• circuit_breaker:{SERVICE}:open
• circuit_breaker:{SERVICE}:half_open
• circuit_breaker:{SERVICE}:total_failures:*

Migration (1.x → 2.x)

Breaking changes:

• Replace CircuitState::OPEN() style calls with native enum values if referenced in your code, e.g. CircuitStateEnum::OPEN.
• CircuitBreakerAdapter::getState(string): CircuitStateEnum now returns the native enum.

Otherwise, CircuitBreaker public API is unchanged.

Development

• Run tests: vendor/bin/phpunit --configuration phpunit.xml
• GitHub Actions runs on PHP 8.1–8.4

License

MIT

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Created by: Gabriel Anhaia — https://www.linkedin.com/in/gabrielanhaia