monkeyphp/circuit-breaker

PHP implementation of the circuit breaker pattern

dev-develop 2014-03-19 19:34 UTC

Requires (Dev)

• phpspec/phpspec: 2.0.*@dev

GPL

• David White

• client
• circuit breaker

README

PHP implementation of the Circuit Breaker pattern

A CircuitBreaker is an production pattern, described by Robert T Nygard in his seminal book 'Release It!' [insert amazon link here].

It is a defensive pattern aimed at reducing and eliminating the risk of any integration point within your application, such as third party web service; from affecting the rest of your application.

For example, if your application requires a call to be made to a third party api that is out of the scope of your control, and that service begins to respond slowly to requests made to it; this can slow down the responsiveness of your application in servicing client requests. This in turn can create a cascading failure in your application that may lead to complete failure.

The CircuitBreaker works by monitoring the integration point, in the case of this library by passing requests and responses to a Policy object.

States

A circuit breaker can be in one of three states:

• Open
• Half-open
• Closed

Policy Object

The Policy object can determine if the request is allowed to pass through to the integration point or not. It also is used to inspect the responses from the third party integration and may then decide to prevent and further requests to be allowed to pass through to the integration point.

The Policy instance must only implement two methods request and response and only needs to return a boolean.

In the case of request the returned boolean will determine if the CircuitBreaker should continue to pass the request on to the integration.

In the case of response the returned boolean is used to determine if the CircuitBreaker should return an OpenException to the calling client.

$service = new CircuitBreaker(new FlakeyService(), new PolicyProvider());

$response = $myService->doSomething($request);