Circuit breaker in PHP

This package provides an implementation of the circuit breaker pattern in PHP. You can find more info about it here.

Installation

You can install the package via composer:

composer require stfn/php-circuit-breaker

Usage

Wrap your potentially error-prone function with the circuit breaker, and it will monitor and handle failures.

use Stfn\CircuitBreaker\CircuitBreaker;

$result = CircuitBreaker::for('3rd-party-service')->call(function () {
    // Your function that could fail
});

States

Circuit breaker can have 4 different states.

Closed

In the Closed state, the circuit breaker is fully operational, allowing calls to the 3rd party service. Any exceptions that occur during this state are counted.

Half Open

The Half Open state is a transitional phase where the circuit breaker allows a limited number of calls to the 3rd party service. If these calls are successful, the circuit is closed again. However, if the service continues to exhibit issues, the circuit is moved back to the Open state.

Open

The Open state indicates that the circuit breaker has detected a critical failure, and the call method will fail immediately, throwing a CircuitOpenException exception.

Force Open

Force Open is not part of the regular flow. It can be utilized when intentional suspension of calls to a service is required. In this state, a CircuitOpenException will be thrown.

To force the circuit breaker into the Force Open state, use the following:

use Stfn\CircuitBreaker\CircuitBreaker;

$breaker = CircuitBreaker::for('3rd-party-service')->forceOpenCircuit();

This feature provides a manual override to stop calls to a service temporarily, offering additional control when needed.

Storage

By default, the circuit breaker uses InMemoryStorage as a storage driver, which is not suitable for most of PHP applications.

More useful would be to use RedisStorage.

use Stfn\CircuitBreaker\Storage\RedisStorage;
use Stfn\CircuitBreaker\CircuitBreaker;

$redis = new \Redis();
$redis->connect("127.0.0.1");

$storage = new RedisStorage($redis);

$result = CircuitBreaker::for('3rd-party-service')
    ->storage($storage)
    ->call(function () {
        // Your function that could fail
    });

You could also write your implementation of storage. You should just implement CircuitBreakerStorage interface.

Configuration

Each circuit breaker has default configuration settings, but you can customize them to fit your needs:

use Stfn\CircuitBreaker\CircuitBreaker;

$breaker = CircuitBreaker::for('3rd-party-service')
    ->withOptions([
        'failure_threshold' => 10, // Number of failures triggering the transition to the open state
        'recovery_time' => 120, // Time in seconds to keep the circuit breaker open before attempting recovery
        'sample_duration' => 60, // Duration in seconds within which failures are counted
        'consecutive_success' => 3 // Number of consecutive successful calls required to transition from half open to closed state
    ]);

Excluding some failures

Change the circuit breaker behavior by configuring it to exclude certain types of failures:

use Stfn\CircuitBreaker\CircuitBreaker;

$breaker = CircuitBreaker::for('3rd-party-service')
    ->skipFailureCount(function ($exception) {
        return $exception->getCode() < 500;
    });

Listeners

You can add listeners for circuit breaker actions by extending the CircuitBreakerListener class:

use Stfn\CircuitBreaker\CircuitBreakerListener;
use Stfn\CircuitBreaker\CircuitState;

class LoggerListener extends CircuitBreakerListener
{
    public function beforeCall(CircuitBreaker $breaker, \Closure $action,...$args) : void
    {
        Log::info("before call");    
    }
    
    public function onSuccess(CircuitBreaker $breaker, $result): void
    {
        Log::info($result);
    }

    public function onFail(CircuitBreaker $breaker, $exception) : void
    {
        Log::info($exception);
    }
    
    public function onStateChange(CircuitBreaker $breaker, CircuitState $previousState, CircuitState $newState)
    {
        Log::info($previousState, $newState);
    }
}

Attach the listener to the circuit breaker:

use Stfn\CircuitBreaker\CircuitBreaker;

$breaker = CircuitBreaker::for('3rd-party-service')
    ->listeners([new LoggerListener()]);

Testing

composer test

License

The MIT License (MIT). Please see License File for more information.