Wrench : CakePHP 3 Maintenance mode plugin

Wrench is a CakePHP 3.X plugin that aims to provide an easy way to implement a Maintenance Mode for your CakePHP website / applications.

Requirements

• PHP >= 5.5.9
• CakePHP >= 3.3.0

About the plugin versions

CakePHP < 3.3.0	CakePHP >= 3.3.0
Wrench 1.X	Wrench 2.X
PHP >= 5.4.16	PHP >= 5.5.9
Uses CakePHP DispatcherFilter mecanism	Uses CakePHP Middleware Stack and PSR-7 Request / Response implementation

Recommanded package

If you want to create your own maintenance mode, you can use the CakePHP 3 Bake plugin

Installation

You can install this plugin into your CakePHP application using composer.

The recommended way to install composer packages is:

composer require havokinspiration/wrench

Loading the plugin

You can load the plugin using the shell command:

bin/cake plugin load Wrench

Or you can manually add the loading statement in the boostrap.php file of your application:

Plugin::load('Wrench');

Usage

The plugin is built around a Middleware that will intercept the current request to return a customized response to warn the user that the website / app is undergoing maintenance.

To use the Maintenance mode, you need to add the MaintenanceMiddleware to the MiddlewareStack in your Application file by adding the following elements :

use Wrench\Middleware\MaintenanceMiddleware;

// ...

public function middleware($middleware)
{
    $middleware->add(new MaintenanceMiddleware());
    
    // Other middleware configuration
    
    return $middleware;
}

Since this Middleware is here to prevent the application from responding, it should be the first to be treated by the Dispatcher and should, as such, be configured as the first one, either by adding it in the beginning of the method with the push() method or using the prepend() method anywhere you want in your middlewares configuration.

By default, only adding it with the previous line will make use of the Redirect mode. More informations on maintenance Modes below.

The Middleware is only active when the Configure key Wrench.enable is equal to true. To enable the maintenance mode, use the following statement in your bootstrap.php file :

Configure::write('Wrench.enable', true);

Modes

The plugin is built around the concept of "modes". Modes are special classes which will have the task of processing the request and return the proper response in order to warn the user that the website / application is undergoing maintenance.

The plugin comes packaged with four maintenance modes : Redirect, Output, Callback and View.

You can configure it to use specific modes when adding the Middleware to the Middleware stack by passing parameters to the Middleware constructor. The will result in a call looking like this :

$middleware->add(new MaintenanceMiddleware([
    'mode' => [
        'className' => 'Full\Namespace\To\Mode',
        'config' => [
            // Specific configuration parameters for the Mode
        ]
    ]
]);

If you need it, you can directly pass an instance of a Mode to the mode array key of the filter's config:

$middleware->add(new MaintenanceMiddleware([
    'mode' => new \Wrench\Mode\Redirect([
        'url' => 'http://example.com/maintenance'
    ])
]);

Redirect Mode

The Redirect Mode is the default one. It will perform a redirect to a specific URL. The Redirect Mode accepts the following parameters :

• url : The URL where the redirect should point to. Default to the app base path pointing to a maintenance.html page.
• code : The HTTP status code of the redirect response. The code should be in the 3XX range, otherwise, it might get overwritten. Default to 307.
• headers : Array of additional headers to pass along the redirect response. Default to empty.

You can customize all those parameters :

$middleware->add(new MaintenanceMiddleware([
    'mode' => [
        'className' => 'Wrench\Mode\Redirect',
        'config' => [
            'url' => 'http://example.com/maintenance',
            'code' => 303,
            'headers' => ['someHeader' => 'someValue']
        ]
    ]
]);

Output Mode

The Output Mode allows you to display the content of a static file as a response for the maintenance status. It accepts multiple parameters :

• path : the absolute path to the file that will be served. Default to {ROOT}/maintenance.html.
• code : The HTTP status code of the redirect response. Default to 503.
• headers : Array of additional headers to pass along the redirect response. Default to empty.

You can customize all those parameters :

$middleware->add(new MaintenanceMiddleware([
    'mode' => [
        'className' => 'Wrench\Mode\Output',
        'config' => [
            'path' => '/path/to/my/file',
            'code' => 404,
            'headers' => ['someHeader' => 'someValue']
        ]
    ]
]);

Callback Mode

The Callback Mode gives you the ability to use a custom callable. It accepts only one parameter callback which should be a callable. The callable will take two arguments :

• request : A \Psr\Http\Message\ServerRequestInterface instance
• response : A \Psr\Http\Message\ResponseInterface instance

The callable is expected to return a \Psr\Http\Message\ResponseInterface if the request is to be stopped.

$middleware->add(new MaintenanceMiddleware([
    'mode' => [
        'className' => 'Wrench\Mode\Callback',
        'config' => [
            'callback' => function($request, $response) {
                $string = 'Some content from a callback';

                $stream = new Stream(fopen('php://memory', 'r+'));
                $stream->write($string);
                $response = $response->withBody($stream);
                $response = $response->withStatus(503);
                $response = $response->withHeader('someHeader', 'someValue');
                return $response;
            }
        ]
    ]
]);

View Mode

The View Mode gives you the ability to use a View to render the maintenance page. This gives you the ability to leverage helpers and the layout / template system of the framework. It accepts multiple parameters :

• code : The HTTP status code of the redirect response. Default to 503.
• headers : Array of additional headers to pass along the redirect response. Default to empty.
• view : Array of parameters to pass to the View class constructor. Only the following options are supported :
  • className : Fully qualified class name of the View class to use. Default to AppView
  • templatePath : Path to the template you wish to display (relative to your src/Template directory). You can use plugin dot notation.
  • template : Template name to use. Default to "maintenance".
  • plugin : Theme where to find the layout and template
  • theme : Same thing than plugin
  • layout : Layout name to use. Default to "default"
  • layoutPath : Path to the layout you wish to display (relative to your src/Template directory). You can use plugin dot notation. Default to "Layout"

// Will load a template ``src/Template/Maintenance/maintenance.ctp``
// in a layout ``src/Template/Layout/Maintenance/maintenance.ctp``
$middleware->add(new MaintenanceMiddleware([
    'mode' => [
        'className' => 'Wrench\Mode\View',
        'config' => [
            'view' => [
                 'templatePath' => 'Maintenance',
                 'layout' => 'maintenance',
                 'layoutPath' => 'Maintenance'
            ]
        ]
    ]
]);

Creating a custom mode

If you have special needs, you can create your own maintenance mode. To get started quickly, you can use the bake console tool to generate a skeleton:

bin/cake bake maintenance_mode MyCustomMode

This will generate a MyCustomMode class file under the App\Maintenance\Mode namespace (as well as a test file). Your skeleton will only contain one method process() returning a \Psr\Http\Message\ResponseInterface object. This is where the logic of your maintenance mode goes. You can either make the method return a ResponseInterface object which will shortcut the request cycle and use the returned ResponseInterface object to respond to the request. Any other returned value will make the maintenance mode no-op and the request cycle will go on. This is useful if you need to display the maintenance status only on specific conditions.

The Mode implements the InstanceConfigTrait which allows you to easily define default configuration parameters and gives you easy access to them.

Keep in mind that the ResponseInterface you need to return is PSR-7 compliant. You can get more details about the implementation and how to interact with it on the PHP-FIG website as well as on the CakePHP documentation

You can check out the implemented modes to have some examples.

Conditionally applying the maintenance mode

Conditionally applying a middleware is currently not possible with the current implementation of the Middleware stack in CakePHP 3.3. A documentation on how to do this will be added when and if this feature is implemented in the core.

Contributing

If you find a bug or would like to ask for a feature, please use the GitHub issue tracker. If you would like to submit a fix or a feature, please fork the repository and submit a pull request.

Coding standards

Since this plugin is tangled with features from the CakePHP Core and to provide consistency, it follows the CakePHP coding standards. When submitting a pull request, make sure your code follows these standards. You can check it by installing the code sniffer :

composer require cakephp/cakephp-codesniffer:dev-master

And then running the sniff :

./vendor/bin/phpcs -p --extensions=php --standard=vendor/cakephp/cakephp-codesniffer/CakePHP ./src ./tests

License

Copyright (c) 2015 - 2017, Yves Piquel and licensed under The MIT License. Please refer to the LICENSE.txt file.