Wal3fo Laravel Sentinel

Production-ready circuit breaker for Laravel queues and service calls, built to stop cascading failures with closed, open, and half-open states.

Introduction

When a dependency starts failing (mail API, payment gateway, CRM, webhook target), retries alone can overload workers and amplify outages. A circuit breaker prevents that by temporarily short-circuiting failing paths, then probing recovery in a controlled way.

Wal3fo Laravel Sentinel is designed for Laravel queue-heavy applications where resilience and predictable failure handling matter. Use it when:

• jobs call unstable or rate-limited external services
• multiple workers can overwhelm a failing dependency
• you need controlled backoff and safe recovery behavior
• you want observable state transitions and operational commands

Features

• Queue middleware for automatic circuit checks and job release behavior
• Full circuit lifecycle: closed, open, half_open
• Cache-backed state and counters (Redis strongly recommended)
• Per-service configuration overrides
• Pluggable failure classification via contract
• Artisan commands for status and manual control
• Transition events for monitoring and alerting
• Laravel 10, 11, 12, and 13 support

Installation

composer require wal3fo/laravel-sentinel

Publish the package configuration:

php artisan vendor:publish --tag=sentinel-config

[!TIP] Use Redis as the cache backend for distributed queue workers and reliable lock behavior.

Configuration

Sentinel is configured in config/sentinel.php.

Global defaults are defined under defaults, then selectively overridden per service under services.

<?php

return [
    'defaults' => [
        'threshold' => 50.0,
        'min_requests' => 10,
        'cooldown_seconds' => 60,
        'release_delay_seconds' => 30,
        'half_open_probe_limit' => 1,
    ],

    'services' => [
        'mail' => [
            'threshold' => 40.0,
            'min_requests' => 20,
            'cooldown_seconds' => 120,
            'release_delay_seconds' => 20,
            'half_open_probe_limit' => 1,
        ],

        'crm' => [
            'threshold' => 30.0,
            'min_requests' => 8,
            'cooldown_seconds' => 45,
            'release_delay_seconds' => 15,
        ],
    ],
];

Key Options

• threshold: failure-rate percentage that opens the circuit
• min_requests: minimum attempts required before threshold evaluation
• cooldown_seconds: time to keep the circuit open before half-open probe window
• release_delay_seconds: queue job release delay when circuit is not allowing execution

Per-Service Overrides

Any service key in services inherits from defaults and can override only what it needs.

Basic Usage

Queue Job Middleware

<?php

namespace App\Jobs;

use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Foundation\Bus\Dispatchable;
use Illuminate\Queue\InteractsWithQueue;
use Illuminate\Queue\SerializesModels;
use Wal3fo\LaravelSentinel\Middleware\CircuitBreakerMiddleware;

final class SendEmailJob implements ShouldQueue
{
    use Dispatchable;
    use InteractsWithQueue;
    use Queueable;
    use SerializesModels;

    public function middleware(): array
    {
        return [
            new CircuitBreakerMiddleware('mail'),
        ];
    }

    public function handle(): void
    {
        // Call external provider here.
    }
}

Multiple services in one job:

public function middleware(): array
{
    return [
        new CircuitBreakerMiddleware(['mail', 'crm']),
    ];
}

Attribute Usage

When you prefer declarative service mapping, use the package attribute and instantiate middleware without arguments.

<?php

namespace App\Jobs;

use Illuminate\Contracts\Queue\ShouldQueue;
use Wal3fo\LaravelSentinel\Attributes\UseCircuitBreaker;
use Wal3fo\LaravelSentinel\Middleware\CircuitBreakerMiddleware;

#[UseCircuitBreaker(['mail'])]
final class SendNotificationJob implements ShouldQueue
{
    public function middleware(): array
    {
        return [new CircuitBreakerMiddleware()];
    }

    public function handle(): void
    {
        // Perform work.
    }
}

How It Works

Sentinel tracks attempts and failures per service in cache.

1. closed: requests/jobs flow normally while failures are recorded.
2. open: once min_requests is met and failure_rate >= threshold, executions are short-circuited.
3. half_open: after cooldown_seconds, Sentinel allows limited probes (half_open_probe_limit).
4. On probe success, the circuit closes and counters reset.
5. On probe failure, the circuit re-opens and cooldown restarts.

Failure rate is calculated as:

$$ ext{failure_rate} = \frac{\text{failures}}{\text{attempts}} \times 100 $$

When a queue middleware check finds a circuit open (or half-open without an available probe slot), the job is released using the configured release_delay_seconds.

Failure Classification

By default, Sentinel uses:

• Wal3fo\LaravelSentinel\Services\DefaultFailureClassifier

The default classifier ignores configured business exceptions and counts outage-like exceptions.

To customize behavior, provide your own classifier implementing:

• Wal3fo\LaravelSentinel\Contracts\FailureClassifier

<?php

namespace App\Support;

use Throwable;
use Wal3fo\LaravelSentinel\Contracts\FailureClassifier;

final class ApiFailureClassifier implements FailureClassifier
{
    public function shouldCount(Throwable $throwable, string $service, array $serviceConfig = []): bool
    {
        return ! $throwable instanceof \DomainException;
    }
}

Register it in configuration:

'failure_classifier' => [
    'class' => App\Support\ApiFailureClassifier::class,
],

Artisan Commands

• php artisan sentinel:status Shows status for all configured services.
• php artisan sentinel:status mail Shows detailed status for a single service.
• php artisan sentinel:open mail Forces a service circuit to open.
• php artisan sentinel:close mail Forces a service circuit to closed.
• php artisan sentinel:reset Resets all configured service circuits and counters.
• php artisan sentinel:reset mail Resets one service circuit and counters.

Events

Sentinel dispatches events on state changes:

• Wal3fo\LaravelSentinel\Events\CircuitOpened Fired when a circuit transitions to open.
• Wal3fo\LaravelSentinel\Events\CircuitHalfOpened Fired when cooldown expires and circuit enters half_open.
• Wal3fo\LaravelSentinel\Events\CircuitClosed Fired when recovery succeeds and circuit returns to closed.

Each event extends Wal3fo\LaravelSentinel\Events\CircuitStateChanged and includes service, state, and status data.

Best Practices

• Apply circuit breakers to network or infrastructure-dependent operations, not pure business validation logic.
• Count failures that indicate dependency outage/timeouts; ignore business/domain exceptions where appropriate.
• Use Redis for cache and locks in multi-worker production environments.
• Set min_requests high enough to avoid opening on low-volume noise.
• Tune threshold per dependency based on real-world error patterns and SLOs.

Testing

Run the test suite:

composer test

The package includes coverage for:

• middleware behavior and release flow when circuits are open
• state transitions (closed → open → half_open → closed)
• half-open probe limits
• failure classification rules
• event dispatching
• artisan command behavior

Compatibility

• Laravel: 10, 11, 12, 13
• PHP: ^8.1 (effective minimum follows the selected Laravel version)

Contributing

Contributions are welcome.

1. Fork the repository.
2. Create a feature branch.
3. Add tests for behavioral changes.
4. Run composer test.
5. Open a pull request with a clear description.

License

Released under the MIT License.