Circuit Breaker

More information: https://martinfowler.com/bliki/CircuitBreaker.html

Installation

composer require ksaveras/circuit-breaker

Use cases

Basic example

Simple circuit check using Symfony Redis cache

use Ksaveras\CircuitBreaker\CircuitBreakerFactory;
use Ksaveras\CircuitBreaker\Storage\CacheStorage;
use Ksaveras\CircuitBreaker\Policy\ExponentialRetryPolicy;
use Symfony\Component\Cache\Adapter\RedisAdapter;

$redisAdapter = new RedisAdapter(
    RedisAdapter::createConnection('redis://localhost'),
    // the namespace for circuit breaker storage
    'circuit-breaker',
    // max TTL is set to 24 hours
    86400
);

$factory = new CircuitBreakerFactory(
    // max 3 failures before setting circuit breaker as open
    3,
    new CacheStorage($redisAdapter),
    // exponential retry starting with 30 seconds
    new ExponentialRetryPolicy(30),
);

$circuitBreaker = $factory->create('service-api');

if ($circuitBreaker->isAvailable()) {
    try {
        // call 3rd party service api
        $circuitBreaker->recordSuccess();
    } catch (\Exception $exception) {
        $circuitBreaker->recordFailure();
    }
}

// check if CB is closed
$circuitBreaker->isClosed();

// check if CB is half open
$circuitBreaker->isHalfOpen();

// check if CB is open
$circuitBreaker->isOpen();

// get number of failures
$circuitBreaker->getFailureCount();

// get CB remaining delay in seconds
$circuitBreaker->remainingDelay();

Use callback

use Ksaveras\CircuitBreaker\CircuitBreakerFactory;
use Ksaveras\CircuitBreaker\Storage\CacheStorage;
use Ksaveras\CircuitBreaker\Policy\ExponentialRetryPolicy;
use Symfony\Component\Cache\Adapter\RedisAdapter;

$redisAdapter = new RedisAdapter(
    RedisAdapter::createConnection('redis://localhost'),
    // the namespace for circuit breaker storage
    'circuit-breaker',
    // max TTL is set to 24 hours
    86400
);

$factory = new CircuitBreakerFactory(
    // max 3 failures before setting circuit breaker as open
    3,
    new CacheStorage($redisAdapter),
    // exponential retry starting with 30 seconds
    new ExponentialRetryPolicy(30),
);

$circuitBreaker = $factory->create('service-api');

try {
    $result = $circuitBreaker->call(
        function () {
            $this->callApi();
        }
    );
} catch (OpenCircuitException $exception) {
    // Open circuit
} catch (\Exception $exception) {
    // 3rd party exception
}

Use Retry-After response header policy

use Ksaveras\CircuitBreaker\CircuitBreakerFactory;
use Ksaveras\CircuitBreaker\HeaderPolicy\PolicyChain;
use Ksaveras\CircuitBreaker\HeaderPolicy\RateLimitPolicy;
use Ksaveras\CircuitBreaker\HeaderPolicy\RetryAfterPolicy;
use Ksaveras\CircuitBreaker\Policy\ExponentialRetryPolicy;
use Ksaveras\CircuitBreaker\Storage\CacheStorage;
use Symfony\Component\Cache\Adapter\RedisAdapter;

$redisAdapter = new RedisAdapter(
    RedisAdapter::createConnection('redis://localhost'),
    // the namespace for circuit breaker storage
    'circuit-breaker',
    // max TTL is set to 24 hours
    86400
);

$factory = new CircuitBreakerFactory(
    // max 3 failures before setting circuit breaker as open
    3,
    new CacheStorage($redisAdapter),
    // exponential retry starting with 30 seconds
    new ExponentialRetryPolicy(30),
    // check for Retry-After or X-Rate-Limit-Reset headers
    new PolicyChain(
        new RetryAfterPolicy(),
        new RateLimitPolicy(),
    ),
);

$circuitBreaker = $factory->create('service-api');

// \Psr\Http\Message\ResponseInterface
$response = $apiClient->call();

// Too Many Requests
if ($response->getStatusCode() === 429) {
    $circuitBreaker->recordRequestFailure($response);
}

Tests

composer test

Code Quality

composer static-analysis