Laravel Circuit Breaker

Circuit breaker is a design pattern used in software development. It is used to detect failures and encapsulates the logic of preventing a failure from constantly recurring, during maintenance, temporary external system failure or unexpected system difficulties.

Source: Wikipedia

Further explanation

Let's explain what this does using an example, as they are much better than definitions, in my opinion.

Let's say you have two microservices A and B:

1. You are calling microservice B from A and have a 30s timeout configured.
2. B fails to respond and you receive a timeout error.
3. You keep getting requests to A and keep failing with a timeout from B.
4. Request queue of A gets filled up.
5. Requests to A start to timeout.

In this case it would be much better to track request failures from A to B and return an error immediately.

Circuit Breaker pattern does just that - on A you are tracking request failures to B and if failure count, in the particular time window, exceeds threshold, you skip doing those requests and return an error immediately.

Installation

1. Run:

composer require lukaszaleckas/laravel-circuit-breaker

Service provider should be automatically registered, if not add

LaravelCircuitBreaker\CircuitBreakerServiceProvider::class

to your application's app.php.

2. Publish circuit-breaker.php config file:

    php artisan vendor:publish --tag=circuit-breaker

Usage

Inject LaravelCircuitBreaker\CircuitBreakerService through constructor.

Use getCircuitBreaker with service name passed as a parameter to get a circuit breaker instance.

Method usage:

• Use isClosed in your, for example, HTTP client to determine if requests can be made.
• Use registerFailure when you receive an error.
• Use registerSuccess when you receive a success response. This is used to close the circuit when/if it's half open.