Guzzle 6 Circuit-Breaker Middleware
, (*1)
This is a Guzzle 6 middleware that integrates https://github.com/ejsmont-artur/php-circuit-breaker., (*2)
Contents
Requirements
Dependencies
| Dependency |
Version |
Reason |
php |
~7.0 |
Anything lower has (almost) reached EOL |
guzzlephp/promises |
~6.2 |
Middlewares pass Promises around |
psr/http-message |
~1.0 |
Standardization, doh |
ejsmont-artur/php-circuit-breaker |
~0.1 |
Simple and robust Circuit Breaker implementation for PHP |
Installation
This library is installed via composer., (*3)
composer require "flix-tech/guzzle-circuit-breaker-middleware=~1.0"
Usage
NOTE
It is recommended that this middleware is on top of the stack so that if a service is unavailable, it can instantly
reject without going further down the chain., (*4)
With the default configuration, this middleware will inspect the PSR-7 requests for either a transport option key
"circuit_breaker.requested_service_name" exposed via Middleware::CB_TRANSFER_OPTION_KEY in the request options
array, or a request header "X-CB-Service-Name" exposed via Middleware::CB_SERVICE_NAME_HEADER. You can pass an own
service name extractor callable that takes the form f(RequestInterface $request, array $requestOptions): string., (*5)
The service name will be used to look up the
availability in the circuit breaker. If it is not available, it will be instantly rejected with a
CircuitBreakerIsClosedException., (*6)
If the request was successful, the middleware will report a success to the circuit breaker for the given service.
Otherwise it will report a failure and pass the rejection further down the chain., (*7)
You can pass a custom exception map into the middleware with which you can control which exception types and values
should actually trigger a failure report. I.e. a 404 might be a failed configuration issue and might not trigger failure
reports. The exception map callback takes the form f($rejectedValue): bool., (*8)
Example
<?php
use Ejsmont\CircuitBreaker\Factory;
use FlixTech\CircuitBreakerMiddleware\Middleware;
use GuzzleHttp\Client;
use GuzzleHttp\Exception\RequestException;
use GuzzleHttp\HandlerStack;
use GuzzleHttp\Handler\CurlHandler;
use Psr\Http\Message\RequestInterface;
$circuitBreaker = Factory::getSingleApcInstance();
$serviceNameExtractor = function (RequestInterface $request, array $options) {
if (\array_key_exists('my_custom_option_key', $options)) {
return $options['my_custom_option_key'];
}
return null;
};
$exceptionMap = function ($rejectedValue) {
if ($rejectedValue instanceof RequestException && $rejectedValue->getResponse()) {
return 404 !== $rejectedValue->getResponse()->getStatusCode();
}
return true;
};
$middleware = new Middleware(
$circuitBreaker,
$serviceNameExtractor,
$exceptionMap
);
$handlerStack = HandlerStack::create(new CurlHandler());
$handlerStack->push($middleware);
$client = new Client(['handler' => $handlerStack]);
Testing
To run the tests, just run ./vendor/bin/phpunit from the root of the project after installing the dev requirements., (*9)
Contributing
In order to contribute to this library, follow this workflow:, (*10)
- Fork the repository
- Create a feature branch
- Work on the feature
- Run tests to verify that the tests are passing
- Open a PR to the upstream
master branch
- See any Travis CI messages popping up on your PR
- Be happy about contributing to open source!
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