Ganesha is PHP implementation of Circuit Breaker pattern which has multi strategies to avoid cascading failures and supports various storages to record statistics.
If Ganesha is saving your service from system failures, please consider donating to this project's author, Akihito Nakano, to show your ❤️ and support. Thank you!
This is one of the Circuit Breaker implementation in PHP which has been actively developed and production ready - well-tested and well-documented. 💪 You can integrate Ganesha to your existing code base easily as Ganesha provides just simple interfaces and Guzzle Middleware behaves transparency.
If you have an idea about enhancement, bugfix..., please let me know via Issues. ✨
- Ganesha
- Table of contents
- Are you interested?
- Unveil Ganesha
- Usage
- Strategies
- Adapters
- Customizing storage keys
- Ganesha ❤️ Guzzle
- Ganesha ❤️ OpenAPI Generator
- Ganesha ❤️ Symfony HttpClient
- Companies using Ganesha 🚀
- The articles/videos Ganesha loves ✨ 🐘 ✨
- Run tests
- Requirements
- Build promotion site with Soushi
- Author
Here is an example which shows you how Ganesha behaves when a failure occurs.
It is easily executable. All you need is Docker.
# Install Composer
$ curl -sS https://getcomposer.org/installer | php
# Run the Composer command to install the latest version of Ganesha
$ php composer.phar require ackintosh/ganesha
Ganesha provides following simple interfaces. Each method receives a string (named $service
in example) to identify the service. $service
will be the service name of the API, the endpoint name, etc. Please remember that Ganesha detects system failure for each $service
.
$ganesha->isAvailable($service);
$ganesha->success($service);
$ganesha->failure($service);
// For further details about builder options, please see the `Strategy` section.
$ganesha = Ackintosh\Ganesha\Builder::withRateStrategy()
->adapter(new Ackintosh\Ganesha\Storage\Adapter\Redis($redis))
->failureRateThreshold(50)
->intervalToHalfOpen(10)
->minimumRequests(10)
->timeWindow(30)
->build();
$service = 'external_api';
if (!$ganesha->isAvailable($service)) {
die('external api is not available');
}
try {
echo \Api::send($request)->getBody();
$ganesha->success($service);
} catch (\Api\RequestTimedOutException $e) {
// If an error occurred, it must be recorded as failure.
$ganesha->failure($service);
die($e->getMessage());
}
(martinfowler.com : CircuitBreaker)
Ganesha follows the states and transitions described in the article faithfully. $ganesha->isAvailable()
returns true
if the circuit states on Closed
, otherwise it returns false
.
- When the circuit state transitions to
Open
the eventGanesha::EVENT_TRIPPED
is triggered - When the state back to
Closed
the eventGanesha::EVENT_CALMED_DOWN
is triggered
$ganesha->subscribe(function ($event, $service, $message) {
switch ($event) {
case Ganesha::EVENT_TRIPPED:
\YourMonitoringSystem::warn(
"Ganesha has tripped! It seems that a failure has occurred in {$service}. {$message}."
);
break;
case Ganesha::EVENT_CALMED_DOWN:
\YourMonitoringSystem::info(
"The failure in {$service} seems to have calmed down :). {$message}."
);
break;
case Ganesha::EVENT_STORAGE_ERROR:
\YourMonitoringSystem::error($message);
break;
default:
break;
}
});
If disabled, Ganesha keeps to record success/failure statistics, but Ganesha doesn't trip even if the failure count reached to a threshold.
// Ganesha with Count strategy(threshold `3`).
// $ganesha = Ackintosh\Ganesha\Builder::withCountStrategy() ...
// Disable
Ackintosh\Ganesha::disable();
// Although the failure is recorded to storage,
$ganesha->failure($service);
$ganesha->failure($service);
$ganesha->failure($service);
// Ganesha does not trip and Ganesha::isAvailable() returns true.
var_dump($ganesha->isAvailable($service));
// bool(true)
Resets the statistics saved in a storage.
$ganesha = Ackintosh\Ganesha\Builder::withRateStrategy()
// ...
->build();
$ganesha->reset();
Ganesha has two strategies which avoids cascading failures.
$ganesha = Ackintosh\Ganesha\Builder::withRateStrategy()
// The interval in time (seconds) that evaluate the thresholds.
->timeWindow(30)
// The failure rate threshold in percentage that changes CircuitBreaker's state to `OPEN`.
->failureRateThreshold(50)
// The minimum number of requests to detect failures.
// Even if `failureRateThreshold` exceeds the threshold,
// CircuitBreaker remains in `CLOSED` if `minimumRequests` is below this threshold.
->minimumRequests(10)
// The interval (seconds) to change CircuitBreaker's state from `OPEN` to `HALF_OPEN`.
->intervalToHalfOpen(5)
// The storage adapter instance to store various statistics to detect failures.
->adapter(new Ackintosh\Ganesha\Storage\Adapter\Memcached($memcached))
->build();
Note about "time window": The Storage Adapter implements either SlidingTimeWindow or TumblingTimeWindow. The difference of the implementation comes from constraints of the storage functionalities.
- SlidingTimeWindow implements a time period that stretches back in time from the present. For instance, a SlidingTimeWindow of 30 seconds includes any events that have occurred in the past 30 seconds.
- Redis adapter and MongoDB adapter implements SlidingTimeWindow.
The details to help us understand visually is shown below:
(quoted from Introduction to Stream Analytics windowing functions - Microsoft Azure)
- TumblingTimeWindow implements time segments, which are divided by a value of
timeWindow
. - APCu adapter and Memcached adapter implement TumblingTimeWindow.
The details to help us understand visually is shown below:
(quoted from Introduction to Stream Analytics windowing functions - Microsoft Azure)
If you want use the Count strategy use Builder::buildWithCountStrategy()
to build an instance.
$ganesha = Ackintosh\Ganesha\Builder::withCountStrategy()
// The failure count threshold that changes CircuitBreaker's state to `OPEN`.
// The count will be increased if `$ganesha->failure()` is called,
// or will be decreased if `$ganesha->success()` is called.
->failureCountThreshold(100)
// The interval (seconds) to change CircuitBreaker's state from `OPEN` to `HALF_OPEN`.
->intervalToHalfOpen(5)
// The storage adapter instance to store various statistics to detect failures.
->adapter(new Ackintosh\Ganesha\Storage\Adapter\Memcached($memcached))
->build();
The APCu adapter requires the APCu extension.
$adapter = new Ackintosh\Ganesha\Storage\Adapter\Apcu();
$ganesha = Ackintosh\Ganesha\Builder::withRateStrategy()
->adapter($adapter)
// ... (omitted) ...
->build();
Note: APCu is internal to each server/instance, not pooled like most Memcache and Redis setups. Each worker's circuit breaker will activate or reset individually, and failure thresholds should be set lower to compensate.
Redis adapter requires phpredis or Predis client instance. The example below is using phpredis.
$redis = new \Redis();
$redis->connect('localhost');
$adapter = new Ackintosh\Ganesha\Storage\Adapter\Redis($redis);
$ganesha = Ackintosh\Ganesha\Builder::withRateStrategy()
->adapter($adapter)
// ... (omitted) ...
->build();
Memcached adapter requires memcached (NOT memcache) extension.
$memcached = new \Memcached();
$memcached->addServer('localhost', 11211);
$adapter = new Ackintosh\Ganesha\Storage\Adapter\Memcached($memcached);
$ganesha = Ackintosh\Ganesha\Builder::withRateStrategy()
->adapter($adapter)
// ... (omitted) ...
->build();
MongoDB adapter requires mongodb extension.
$manager = new \MongoDB\Driver\Manager('mongodb://localhost:27017/');
$adapter = new Ackintosh\Ganesha\Storage\Adapter\MongoDB($manager, 'dbName', 'collectionName');
$ganesha = Ackintosh\Ganesha\Builder::withRateStrategy()
->adapter($adapter)
// ... (omitted) ...
->build();
If you want customize the keys to be used when storing circuit breaker information, set an instance which implements StorageKeysInterface.
class YourStorageKeys implements StorageKeysInterface
{
public function prefix()
{
return 'your_prefix_';
}
// ... (omitted) ...
}
$ganesha = Ackintosh\Ganesha\Builder::withRateStrategy()
// The keys which will stored by Ganesha to the storage you specified via `adapter`
// will be prefixed with `your_prefix_`.
->storageKeys(new YourStorageKeys())
// ... (omitted) ...
->build();
If you are using Guzzle (v6 or higher), Guzzle Middleware powered by Ganesha makes it easy to integrate Circuit Breaker to your existing code base.
use Ackintosh\Ganesha\Builder;
use Ackintosh\Ganesha\GuzzleMiddleware;
use Ackintosh\Ganesha\Exception\RejectedException;
use GuzzleHttp\Client;
use GuzzleHttp\HandlerStack;
$ganesha = Builder::withRateStrategy()
->timeWindow(30)
->failureRateThreshold(50)
->minimumRequests(10)
->intervalToHalfOpen(5)
->adapter($adapter)
->build();
$middleware = new GuzzleMiddleware($ganesha);
$handlers = HandlerStack::create();
$handlers->push($middleware);
$client = new Client(['handler' => $handlers]);
try {
$client->get('http://api.example.com/awesome_resource');
} catch (RejectedException $e) {
// If the circuit breaker is open, RejectedException will be thrown.
}
As documented in Usage, Ganesha detects failures for each $service
. Below, We will show you how Guzzle Middleware determine $service
and how we specify $service
explicitly.
By default, the host name is used as $service
.
// In the example above, `api.example.com` is used as `$service`.
$client->get('http://api.example.com/awesome_resource');
You can also specify $service
via a option passed to client, or request header. If both are specified, the option value takes precedence.
// via constructor argument
$client = new Client([
'handler' => $handlers,
// 'ganesha.service_name' is defined as ServiceNameExtractor::OPTION_KEY
'ganesha.service_name' => 'specified_service_name',
]);
// via request method argument
$client->get(
'http://api.example.com/awesome_resource',
[
'ganesha.service_name' => 'specified_service_name',
]
);
// via request header
$request = new Request(
'GET',
'http://api.example.com/awesome_resource',
[
// 'X-Ganesha-Service-Name' is defined as ServiceNameExtractor::HEADER_NAME
'X-Ganesha-Service-Name' => 'specified_service_name'
]
);
$client->send($request);
Alternatively, you can apply your own rules by implementing a class that implements the ServiceNameExtractorInterface
.
use Ackintosh\Ganesha\GuzzleMiddleware\ServiceNameExtractorInterface;
use Psr\Http\Message\RequestInterface;
class SampleExtractor implements ServiceNameExtractorInterface
{
/**
* @override
*/
public function extract(RequestInterface $request, array $requestOptions)
{
// We treat the combination of host name and HTTP method name as $service.
return $request->getUri()->getHost() . '_' . $request->getMethod();
}
}
// ---
$ganesha = Builder::withRateStrategy()
// ...
->build();
$middleware = new GuzzleMiddleware(
$ganesha,
// Pass the extractor as an argument of GuzzleMiddleware constructor.
new SampleExtractor()
);
PHP client generated by OpenAPI Generator is using Guzzle as HTTP client and as we mentioned as Ganesha ❤️ Guzzle, Guzzle Middleware powered by Ganesha is ready. So it is easily possible to integrate Ganesha and the PHP client generated by OpenAPI Generator in a smart way as below.
// For details on how to build middleware please see https://github.com/ackintosh/ganesha#ganesha-heart-guzzle
$middleware = new GuzzleMiddleware($ganesha);
// Set the middleware to HTTP client.
$handlers = HandlerStack::create();
$handlers->push($middleware);
$client = new Client(['handler' => $handlers]);
// Just pass the HTTP client to the constructor of API class.
$api = new PetApi($client);
try {
// Ganesha is working in the shadows! The result of api call is monitored by Ganesha.
$api->getPetById(123);
} catch (RejectedException $e) {
awesomeErrorHandling($e);
}
If you are using Symfony HttpClient, GaneshaHttpClient makes it easy to integrate Circuit Breaker to your existing code base.
use Ackintosh\Ganesha\Builder;
use Ackintosh\Ganesha\GaneshaHttpClient;
use Ackintosh\Ganesha\Exception\RejectedException;
$ganesha = Builder::withRateStrategy()
->timeWindow(30)
->failureRateThreshold(50)
->minimumRequests(10)
->intervalToHalfOpen(5)
->adapter($adapter)
->build();
$client = HttpClient::create();
$ganeshaClient = new GaneshaHttpClient($client, $ganesha);
try {
$ganeshaClient->request('GET', 'http://api.example.com/awesome_resource');
} catch (RejectedException $e) {
// If the circuit breaker is open, RejectedException will be thrown.
}
As documented in Usage, Ganesha detects failures for each $service
. Below, We will show you how GaneshaHttpClient determine $service
and how we specify $service
explicitly.
By default, the host name is used as $service
.
// In the example above, `api.example.com` is used as `$service`.
$ganeshaClient->request('GET', 'http://api.example.com/awesome_resource');
You can also specify $service
via a option passed to client, or request header. If both are specified, the option value takes precedence.
// via constructor argument
$ganeshaClient = new GaneshaHttpClient($client, $ganesha, [
// 'ganesha.service_name' is defined as ServiceNameExtractor::OPTION_KEY
'ganesha.service_name' => 'specified_service_name',
]);
// via request method argument
$ganeshaClient->request(
'GET',
'http://api.example.com/awesome_resource',
[
'ganesha.service_name' => 'specified_service_name',
]
);
// via request header
$ganeshaClient->request('GET', '', ['headers' => [
// 'X-Ganesha-Service-Name' is defined as ServiceNameExtractor::HEADER_NAME
'X-Ganesha-Service-Name' => 'specified_service_name'
]]);
Alternatively, you can apply your own rules by implementing a class that implements the ServiceNameExtractorInterface
.
use Ackintosh\Ganesha\HttpClient\HostTrait;
use Ackintosh\Ganesha\HttpClient\ServiceNameExtractorInterface;
final class SampleExtractor implements ServiceNameExtractorInterface
{
use HostTrait;
/**
* @override
*/
public function extract(string $method, string $url, array $requestOptions): string
{
// We treat the combination of host name and HTTP method name as $service.
return self::extractHostFromUrl($url) . '_' . $method;
}
}
// ---
$ganesha = Builder::withRateStrategy()
// ...
->build();
$ganeshaClient = new GaneshaHttpClient(
$client,
$ganesha,
// Pass the extractor as an argument of GaneshaHttpClient constructor.
new SampleExtractor()
);
As documented in Usage, Ganesha detects failures for each $service
.
Below, We will show you how GaneshaHttpClient specify failure explicitly.
By default Ganesha considers a request is successful as soon as the server responded, whatever the HTTP status code.
Alternatively, you can use the RestFailureDetector
implementation of FailureDetectorInterface
to specify a list of HTTP Status Code to be considered as failure via an option passed to client.
This implementation will consider failure when these HTTP status codes are returned by the server:
- 500 (Internal Server Error)
- 502 (Bad Gateway or Proxy Error)
- 503 (Service Unavailable)
- 504 (Gateway Time-out)
- 505 (HTTP Version not supported)
// via constructor argument
$ganeshaClient = new GaneshaHttpClient(
$client, $ganesha, null,
new RestFailureDetector([503])
);
// via request method argument
$ganeshaClient->request(
'GET',
'http://api.example.com/awesome_resource',
[
// 'ganesha.failure_status_codes' is defined as RestFailureDetector::OPTION_KEY
'ganesha.failure_status_codes' => [503],
]
);
Alternatively, you can apply your own rules by implementing a class that implements the FailureDetectorInterface
.
use Ackintosh\Ganesha\HttpClient\FailureDetectorInterface;
use Symfony\Contracts\HttpClient\Exception\ExceptionInterface;
use Symfony\Contracts\HttpClient\ResponseInterface;
final class SampleFailureDetector implements FailureDetectorInterface
{
/**
* @override
*/
public function isFailureResponse(ResponseInterface $response, array $requestOptions): bool
{
try {
$jsonData = $response->toArray();
} catch (ExceptionInterface $e) {
return true;
}
// Server is not RestFull and always returns HTTP 200 Status Code, but set an error flag in the JSON payload.
return true === ($jsonData['error'] ?? false);
}
/**
* @override
*/
public function getOptionKeys(): array
{
// No option is defined for this implementation
return [];
}
}
// ---
$ganesha = Builder::withRateStrategy()
// ...
->build();
$ganeshaClient = new GaneshaHttpClient(
$client,
$ganesha,
null,
// Pass the failure detector as an argument of GaneshaHttpClient constructor.
new SampleFailureDetector()
);
Here are some companies using Ganesha in production! We are proud of them. 🐘
To add your company to the list, please visit README.md and click on the icon to edit the page or let me know via issues/twitter.
(alphabetical order)
Here are some articles/videos introduce Ganesha! All of them are really shining like a jewel for us. ✨
- 2020/12/21 장애 확산을 막기 위한 서킷브레이커 패턴을 PHP에서 구현해보자
- 2020/04/22 PHP Annotated – April 2020 | PhpStorm Blog
- 2020/03/23 Circuit Breaker - SarvenDev
- 2020/03/23 PHP-Дайджест № 177 (23 марта – 6 апреля 2020) / Хабр
- 2019/08/01 PHP Weekly. Archive. August 1, 2019. News, Articles and more all about PHP
- 2019/07/15 PHP Annotated – July 2019 | PhpStorm Blog
- 2019/04/25 PHP Weekly. Archive. April 25, 2019. News, Articles and more all about PHP
- 2019/03/18 A Semana PHP - Edição Nº229 | Revue
- 2018/06/08 Безопасное взаимодействие в распределенных системах / Блог компании Badoo / Хабр
- 2018/01/22 PHP DIGEST #12: NEWS & TOOLS (JANUARY 1 - JANUARY 14, 2018)
We can run unit tests on a Docker container, so it is not necessary to install the dependencies in your machine.
# Start redis, memcached server
$ docker-compose up
# Run tests in container
$ docker-compose run --rm -w /tmp/ganesha -u ganesha client vendor/bin/phpunit
- Ganesha supports PHP 7.1 or higher.
- An extension or client library which is used by the storage adapter you've choice will be required. Please check the Adapters section for details.
Ganesha © ackintosh, Released under the MIT License.
Authored and maintained by ackintosh
GitHub @ackintosh / Twitter @NAKANO_Akihito / Blog (ja)