README

Introduction

This package provides a middleware which allows you to add "tagging" capabilties to the Symfony HTTPCache.

What this means is that you can associate responses with tags, which can later be invalidated. What THIS means is that you can cache your responses indefinitely and invalidate them only when the content on the page changes.

Features

• Middleware to add tagging capability to the Symfony HTTP Cache.
• Configurable and extensible tag storage.
• Local and remote tag invalidation.
• Configurable HTTP headers.
• Configurable tag encoding.

Quick Start

Installation

Require the library with composer:

$ composer require dtl/http-cache-tagging

You will need a storage strategy, it is easiest to use the DoctrineCache strategy, and for this you will need the doctrine/cache package:

$ composer require doctrine/cache

Wrapping the kernel

use Doctrine\Common\Cache\PhpFileCache;
use Symfony\Component\HttpKernel\HttpCache\Store;
use Symfony\Component\HttpKernel\HttpCache\HttpCache;
use DTL\Symfony\HttpCacheTagging\Storage\DoctrineCache;
use DTL\Symfony\HttpCacheTagging\Manager\TagManager;
use DTL\Symfony\HttpCacheTagging\TaggingKernel;

// your main application
$app = new TestKernel();

// the standard Symfony HTTP cache
$store = new Store('/path/to/keep/cache');
$httpCache = new HttpCache($app, $store);

// our tag storage strategy
$tagStorage = new DoctrineCache(new PhpFileCache('/path/to/keep/tags'));
$tagManager = new TagManager($tagStorage, $store);

// now you can procss the request
$app = new TaggingKernel($httpCache, $tagManager);
$app->handle(Request::create());

Tagging your response

To tag the response just add the tags to the configured tag header (X-Cache-Tags by default).

class MyController
{
    // ..
    public function someAction(Request $request)
    {

        $id = 1;
        $entity = $this->entitymanager->find($id);
        $tag = get_class($entity) . $id;

        $response = Response::create($entity->getHelloWorld());
        $response->headers->set('X-Cache-Tags', json_encode([ $tag ]));

        return $response;
    }
}

Note that above we used JSON encode to convert the tags to a string. A JSON encoded string is expected by default, however you may also choose to use comma-seperated value strategy or an encoding system of your choice by sepecifying a callback in the tag_encoding option.

Invalidating cache entries with tags

Invalidation can be done in three different ways:

• Direct invalidation.
• Request invalidation.
• Response invalidation.

Direct invalidation

Is where you purge the cache directly from your application, for this you will need to inject the TagManager which you instantiated into your Application kernel.

Request invalidation

Is where you send separate HTTP request to the caching server or servers. By default this should be a POST request with the tags encoded in the X-Cache-Invalidate-Tags header.

Note that only request invalidation can be used when you have multiple servers.

Response invalidation

Is where you set the invalidation headers in the HTTP response. This has the same advantage as direct invalidation, but avoids having to inject the tag manager as a service. The X-Cache-Invalidate-Tags header is expected by default.

The response method is probably the most simple:

class MyController
{
    // ...

    public function editAction(Request $request)
    {
        $id = 1;
        $entity = $this->entitymanager->find($id);
        $tag = get_class($entity) . $id;

        // update the entity

        $response = // get your response
        $response->headers->set('X-Cache-Invalidate-Tags', json_encode([ $tag ]));

        return $response;
    }
}

Here we are editing an object which represents a page on your website, we set the response header, after the response has been sent any cache entries which have the entities tag will be removed.

You will also need to update the kernel wrapping to:

$kernel = new TaggingKernel($httpCache, $tagManager, array('invalidate_from_response' => true));

Configuration

• purge_method: Purge method to use when invalidating remotely, note that the Symfony HTTP cache does not support the PURGE method.
• header_tags: Header to use when tagging the response, X-Cache-Tags by default.
• header_invalidate_tags: Header to use for invalidating tags in either request (remote) or response (local). Default is X-Cache-Invalidate-Tags.
• tag_encoding: How the tags should be decoded by the middleware, can be json (default), comma-separate or a PHP callable which will receive the raw tag string and return an array.
• ips: List of IP addresses which may remotely invalidate the cache.

License

This library is released under the MIT license. See the included LICENSE file for more information.