bnomei/kirby3-lapse

Cache any data until set expiration time

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Type:kirby-plugin

2.0.3 2019-09-09 21:48 UTC

README

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Cache any data until set expiration time (with automatic keys).

Commercial Usage

This plugin is free but if you use it in a commercial project please consider to

Installation

  • unzip master.zip as folder site/plugins/kirby3-lapse or
  • git submodule add https://github.com/bnomei/kirby3-lapse.git site/plugins/kirby3-lapse or
  • composer require bnomei/kirby3-lapse

Usecase

The Kirby Pages-Cache can cache the output of Page Templates. It devalidates all cache files if any Object in the Panel is changed. This is a good choice if you do not make changes often. But if you do make changes often you need a cache that knows what has been modified and which caches to devalidate and which not.

Sometimes you can not cache the complete Page since...

  • it contains a form with a csrf hash,
  • you use content security headers with nouces,
  • build and cache data for a logicless templating system like handlebars or
  • you want to cache data from an external source like an API.

Lapse was build to do exactly that: Cache any data until set expiration time.

Usage Examples

For convenience add use Bnomei\Lapse; to the top of your PHP skript.

Example 1: get/set

$key = crc32($page->url()); // unique key
// to delay data creation until need use a callback. do not use a plain array or object.
$data = function () {
    return [1, 2, 3];
}
$data = Lapse::io($key, $data);

Example 2: with custom expiration time

$key = crc32($page->url()); // unique key
$expires = 5; // in minutes. default: 0 aka infinite
$data = function () {
    return [1, 2, 3];
}
$data = Lapse::io($key, $data, $expires);

Example 3: page object

$data = Lapse::io(crc32($page->url()), function () use ($kirby, $site, $page) {
    // create some data
    return [
        'author' => site()->author(),
        'title' => $page->title(),
        'text' => $page->text()->kirbytext(),
        'url' => $page->url(),
    ];
});

Clever keys

Unique but not modified

Caches use a string value as key to store and later retrieve the data. The key is usually a hash of the objects id plus some meta data like the contents language. Storing data related to a Page using the $key = crc32($page->url()); will work just fine. It takes care of the language if you use a multi-language setup since the language is included in the url. But it will expire only if you provide a fixed time or devalidate it yourself.

Modified

The solution is to include the modification timestamp of every object related to the data. So if you store the result of a Page Object with Images being rendered you need to include the modification timestamp of all of these. That will cause the creation of a new cache every time your source changes.

Basic

$keys = [ $page->url().$page->modified() ];
foreach($page->images() as $image) {
    $keys[] = $image->id().$image->modified();
}
$key = crc32(implode($keys));

Objects

Since version 2 of this plugin you can also forward any of these and the key will be magically created for you.

  • Page-Objects,
  • File-Objects and FileVersion-Objects (aka Thumbs),
  • Collections or
  • the Site-Object
$objects = [$page, $page->images()];
$data = Lapse::io($objects, ...)

Multi-language support

The keys created by the plugin are tagged with the current language. You will get a different cache value for each language.

AutoID

If you use the AutoID plugin you can use its modifiedHash() to get a key with modification timestamps at almost zero-cpu-cost.

$zero = modifiedHash($autoidCollectionKey);
$data = Lapse::io($zero, ...)

FAQ

Infinite cache duration by default

Unless you set an expiration when using Lapse::io() the cache file will never devalidate. This is because the plugin is intended to be used with keys defining the expiration like $key = crc32($page->id().$page->modified());.

When using Memcache you need to limit the maximum number of caches created since you have a very limited amount if memory of 64MB at default. You can set a limit at bnomei.lapse.indexLimit to something like 300. But be aware that this makes writing to the cache a tiny bit slower since the plugins internal index must be updated.

No cache when debugging

When Kirbys global debug config is set to true the complete plugin cache will be flushed and no caches will be created. This will make you live easier – trust me.

Kirby Field-Objects and serialization

The plugin uses the default Kirby serialization of objects and since memory references are lost anyway all Kirby Field-Objects are stored by calling their ->value() method. The File-Cache uses a json format.

Migrating from v1 of this plugin

  • lapse helpers method is gone: use Bnomei\Lapse::io().
  • $force param has been removed: use proper keys.
  • all settings have been removed: they are not needed anymore like explained above.

Performance

Use crc32 to generate the hash

crc32 is the fastest hashing algorithm in PHP and the keys do not need to be encrypted.

Cache Driver

For best performance set the global cache driver to one using the servers memory not files on the harddisk (even on SSDs). Memcache or ApcuCache can be activated on most hosting enviroments but rarely are by default. Also see bnomei.lapse.indexLimit setting explained above.

return [
  'cache' => [
    'driver' => 'memcached',
  ],
];

Examples

// lapse v1 could already do this:
// store data until objects are modified with optional expire
$data = Lapse::io(
    $page->id().$page->modified(),
    ['some', 'kind', 'of', 'data'],
    60*24*7 // one week
);

// now it can create magic cache keys from kirby objects
$data = Bnomei\Lapse::io(
    $page, // key with modification date created by lapse based on object 
    function () use ($page) {
        return [
           'title' => $page->title(),
       ];
    }
);

// or from an collection of pages or files
$collection = collection('mycollection');
$data = Lapse::io(
    $collection, // this will turn into a key taking modification date of all objects into consideration
    function () use ($collection) {
        return [ /*...*/ ];
    }
);

// or from an array combining all these
$data = Lapse::io(
    ['myhash', $page, $page->children()->images(), $collection, $site], // will create key from array of objects
    function () use ($site, $page, $collection) {
        return [
            // will not break serialization => automatically store ->value() of fields
            'author' => $site->author(),
            'title' => $page->title(),
            'hero' => $page->children()->images()->first()->srcset()->html(),
            'count' => $collection->count(),
        ];
    }
);

// BONUS: if you use autoid the modified lookups will be at almost zero-cpu cost.

Disclaimer

This plugin is provided "as is" with no guarantee. Use it at your own risk and always test it yourself before using it in a production environment. If you find any issues, please create a new issue.

License

MIT

It is discouraged to use this plugin in any project that promotes racism, sexism, homophobia, animal abuse, violence or any other form of hate speech.

Credits

based on V2 version of