silverstripe-terraformers / keys-for-cache
Silverstripe cache key management
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Type:silverstripe-vendormodule
Requires
- php: ^8.1
- silverstripe/framework: ^5
Requires (Dev)
- phpunit/phpunit: ^9.5
- slevomat/coding-standard: ~8.8.0
- tractorcow/silverstripe-fluent: ^7
README
This module helps you create singular cache keys which can be used as part of any cache strategy, but probably most commonly with Silverstripe's Partial Caching feature.
The overall aim of this module is twofold:
- Make it easier for developers to create cache keys for our
DataObjects
(especially for those that have complex dependencies). - Increase the performance of our applications by reducing the number of, and the complexity of the cache keys that we calculate at the time of an end user's request.
How will we achieve these goals?
We will use and enhance existing config paradigms that Silverstripe developers are already familiar with.
We will move the cost of calculating cache keys to when the changes are made to our DataObjects
, rather than at the
time of an end user's request.
What this module is not:
This module is not here to provide a caching method, it is here to provide you with keys that you can use with your
preferred caching method (EG: partial caching).
- Installation
- Why cache keys are difficult
- How we aim to solve these difficulties
- Setup and configuration
- Performance impact/considerations
- Case Studies
- Fluent support
- Unit testing
- License
- Maintainers
- Development and contribution
Installation
composer require silverstripe-terraformers/keys-for-cache
Requirements
- PHP
^8.1
- Silverstripe Framework
^5
Support for Silverstripe 4 is provided though our ^1
tagged releases.
Why cache keys are difficult
TL;DR: Cache keys need to be updated any time a related piece of information changes, and we often have structures
of content (EG: Carousel blocks) that contain many levels of nested DataObjects
.
The goal of any cache key is to have as low a cost as possible to calculate (as this must happen with every request), but also for it to invalidate at the appropriate times (IE: when a piece of relevant content has changed).
Consider the following:
- We have a
Page
with the Elemental module applied. - One of the blocks available is a Carousel block. This block itself contains Carousel Items, and each Item contains an Image.
- When a change is made to the block itself, to one of its Items, or to any of the Images assigned to its Items, the cache key should be invalidated.
A cache key for a single Carousel block might look something like:
public function getCacheKey(): string { $parts = [ // Parts related to the block itself static::class, $this->ID, $this->LastEdited, // Parts related to the Items within the block $this->Items()->max('LastEdited'), $this->Items()->count(), // Parts related to the Images assigned to our Items Image::get()->filter('ID', $this->Items()->column('ImageID'))->max('LastEdited'), Image::get()->filter('ID', $this->Items()->column('ImageID'))->count(), ]; return implode('-', $parts); }
This can be optimised a bit, but the point is: It requires multiple queries each time it is performed, and it requires a decent chunk of cognitive load to understand (and to come up with in the first place).
In short, we want to achieve the same outcome as the example above, but with a simple configuration, like this:
App\Blocks\CarouselBlock: has_cache_key: true cares: - Items App\Blocks\CarouselItem: cares: - Image
Setup and configuration
Preamble: When we talk about "changes to records", this includes all C.R.U.D. actions.
Relationship config: In order for this module to function, we often need to understand more about the relationships
that your DataObjets
have than perhaps Silverstripe ORM does. More on this here.
Has cache key
First, you need to tell us which DataObjects you would like cache keys to be generated for. For example, we might like a key for all pages and all Elements:
Page: has_cache_key: true DNADesign\Elemental\Models\BaseElement: has_cache_key: true
By adding this configuration, you will have access to the getCacheKey()
method on your DataObject
, and
the $CacheKey
variable in your template when you have that DataObject
in scope.
Next, in order to make sure that your cache keys invalidate when related DataObjects
are updated, you need to define
any dependencies that your model might have.
There are three important configurations to be aware of:
Cares
This configuration determines how $this
DataObject
will be affected when other (related) DataObjects
are
manipulated.
For example: We have requested that all Elements have cache keys. If you have a CarouselBlock
that contains
CarouselItems
, then you will want to make sure that the cache key for the CarouselBlock
is invalidated any time
a CourselItem
is updated.
You can do that by telling us that your CarouselBlock
cares
about its Items
.
App\Blocks\CarouselBlock: cares: - Items
Or in your class:
class CarouselBlock extends BaseElement { private static array $has_many = [ 'Items' => CarouselItem::class, ]; // $owns is optional, but quite common in this use case. I've added it here simply to illustrate how $cares // follows the same paradigm private static array $owns = [ 'Items', ]; private static array $cares = [ 'Items', ]; }
Take the original example where we also wanted our CarouselItem
to include changes to Images as part of its cache key.
We could now also add a cares
config to our CarouselItem
:
App\Blocks\CarouselItem: cares: - Image
Or in your class like so:
class CarouselItem extends DataObject { private static array $has_one = [ 'Image' => Image::class, ]; // $owns is optional, but quite common in this use case. I've added it here simply to illustrate how $cares // follows the same paradigm private static array $owns = [ 'Image', ]; private static array $cares = [ 'Image', ]; }
Now whenever the linked Image
is updated, it will also update the CarouselItem
, and in turn the CarouselItem
will
update the linked Carousel
. Taking this a step further all the way back to Page
, we could also add the following:
# Our BlockPage cares about changes to its ElementalArea App\Elemental\BlockPage: cares: - ElementalArea # Our ElementalAreas care about any changes made to its Elements DNADesign\Elemental\Models\ElementalArea: cares: Elements: BaseElement::class
Our BlockPage
now cares
about our ElementalArea
, and our ElementalArea
now cares about all of its
blocks/elements. This now means that any time a change is made to any of our blocks (so long as we have configured them
similarly to how we have shown with the Carousel
), we will get a new cache key value on our Page
.
Alternatively, you could achieve the same outcome by using Touches.
Important note: Your DataObject
does not need to has_cache_key
in order for it to care
or touch
other
DataObjects
. In fact, we very much rely on you providing us with the full relationship tree through
cares/touches
. We will only generate the cache key for DataObjects
that has_cache_key
, but we will continue to
follow the paths you create until we run out of them.
Important note: Definitely consider the performance consideration of invalidating your Page
cache any time an
element is updated. It has been added above purely as an example of what it technically possible; it has not been added
as a recommendation.
Touches
This configuration determines how $this
DataObject
will affect others when it is updated. EG:
when $this
DataObject
is updated, it should "touch" some other DataObjects
so that they too have their cache keys
invalidated.
Using the example from above, if you have a CarouselBlock
with CarouselItems
then you could alternatively configure
it like so (where the key
is the field relationship name, and the value is the class
that it relates to):
App\Blocks\CarouselItem: touches: - Parent
Or in your class like so:
class CarouselItem extends DataObject { private static array $has_one = [ 'Parent' => CarouselBlock::class, ]; private static array $touches = [ 'Parent', ]; }
This would mean that any time the CarouselItem
is updated it would also update the cache key of the parent
CarouselBlock
.
Alternatively, you could achieve the same outcome by using Cares.
Important note: Your DataObject
does not need to has_cache_key
in order for it to care
or touch
other
DataObjects
. In fact, we very much rely on you providing us with the full relationship tree through
cares/touches
. We will only generate the cache key for DataObjects
that has_cache_key
, but we will continue to
follow the paths you create until we run out of them.
Global cares
You might run into situations where you need your cache key to be updated when any DataObject of a certain class is changed. For example, we could have a "Recent updates block", which lists out the pages that have been most recently updated. For this, we would want to make it so that when any page is updated, it will also invalidate the cache keys for any DataObject that cares about global changes to our pages.
App\Blocks\RecentUpdates: global_cares: - SilverStripe\CMS\Model\SiteTree
Important note: These global updates won't use the touches/cares when they occur. For example,
if Blocks\RecentUpdates
had a touches
of Link: SilverStripe\CMS\Model\SiteTree
, The site tree wouldn't be
updated. This is a mechanism of global updates to ensure we don't run into performance issues
Usage and examples
See: Usage and Examples
Performance impact/considerations
This will increase the queries to the database when DataObjects
are updated, but so far there has been no noticeable
increase to (eg) the publishing time of pages within the CMS, nor has there been any noticeable increase in processing
time of cron jobs related to the manipulation of DataObjects
.
That said:
- You should still be aware of what
cares
andtouches
configuration you enabled. - If you start to notice performance issues with (eg) Publishing a page, then you might need to reconsider the scope
of relationships that you
cares
ortouches
as part of your page and relatedDataObjects
(EG: blocks).
Queued jobs
If you want to prevent content authors from getting slightly slower responses when editing in the CMS, you can queue a
job to generate the cache updates by injecting over CacheKeyExtension
and updating triggerEvent
to create a job then
call CacheRelationService::singleton()->processChange($this->DataObject)
in the job.
Case studies
See: Case studies
Fluent support
See: Fluent support
Unit testing
See: Unit testing
License
See License
Maintainers
- Adrian Humphreys adrhumphreys@gmail.com
- Chris Penny chris.penny@gmail.com
- Adrian Jimson adrian.jimson@silverstripe.com
Development and contribution
If you would like to make contributions to the module please ensure you raise a pull request and discuss with the module maintainers.