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Cache it!Render cache in Drupal 8

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About Wizzlern

Wizzlern

‣ 100% Drupal

‣ Drupal training and consultancy‣ Front-, backend-development ‣ Site administration and editorial‣ Advanced subjects

‣ Since 2009

‣ Active in the Drupal community

‣ Visit us at http://wizzlern.nl

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Program

Drupal 8 Render Cache

‣ D7-D8 differences‣ Cache terminology‣ The thought process‣ Demonstration:

‣ Recent content list‣ Dynamic advertisement

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Caching

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“There  are  only  two  hard  things  in  Computer  Science:  

cache  invalidation  and  naming  things.”

Phil Karlton

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Drupal 7 - Page cache

‣ Core: Cache at page level.

‣ Low complexity cache invalidation.

‣ When a page is edited, the whole page cache is cleared.

‣ When a comment is added, the whole page cache is cleared.

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Drupal 7 - Contrib cache

‣ Cache Expiration and various Varnish modules: High complexity cache invalidation:‣ purge / expire all URLs that contains the changing

content or is referring to it.‣ High invalidation costs.

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Drupal 8 Render Cache

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Drupal 8 strategy

‣ High-complexity cache invalidation

‣ Content invalidated instantaneously

‣ Cached permanently

‣ Cache chaining

‣ Rendered data cached at multiple levels:‣ Page, Block, Entity (node, comment, user, etc.),

View, Menu tree, Text Format filter result, etc.

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Render #cache

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$build['#cache'] = array( 'tags' => ['block_view', 'config:block.block.recentcontent'], 'contexts' => ['languages:language_interface', 'user.permissions'], 'max-age' => Cache::PERMANENT, );

Tags: Where the render result depends on.

Contexts: What makes the render result vary.

Max age: The max time the render result is valid.

For cache variations

To invalidate cache

Render #cache

‣ tags: Identifiers of rendered content. Used for cache invalidation.Example: node:42, user_view, config:image.style.large

‣ contexts: Contexts by which the content may vary.

‣ max-age: The maximum time cached content is valid. Defaults to permanent.

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#cache context

‣ A string that refers to one of the available cache context services.‣ Examples:

‣ https://www.drupal.org/developing/api/8/cache/contexts

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languages :typeroute .menu_active_trails :menu_name .namesessiontheme

timezoneuser .is_super_user .node_grants :operation .permissions .roles :role

Contexts may be hierarchical:parent.child

#cache tags

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class AuthorNameFormatter extends FormatterBase {

public function viewElements(FieldItemListInterface $items) { $elements = array(); foreach ($items as $delta => $item) { /** @var $comment \Drupal\comment\CommentInterface */ $comment = $item->getEntity(); $account = $comment->getOwner(); $elements[$delta] = array( '#theme' => 'username', '#account' => $account, '#cache' => array( 'tags' => $account->getCacheTags() + $comment->getCacheTags(), ), ); } Cache tags for this render element.

Cache should respond to changes in account or comment.

Field formatter for comment author name.

#cache contexts, etc.

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class CommentForm extends ContentEntityForm {

public function form(array $form, FormStateInterface $form_state) {

/** @var \Drupal\comment\CommentInterface $comment */ $comment = $this->entity; $entity = $this->entityManager->getStorage($comment->getCommentedEntityTypeId()) $field_name = $comment->getFieldName(); $field_definition = $this->entityManager->getFieldDefinitions($entity $config = $this->config('user.settings'); // In several places within this function, we vary $form on: // - The current user's permissions. // - Whether the current user is authenticated or anonymous. // - The 'user.settings' configuration. // - The comment field's definition. $form['#cache']['contexts'][] = 'user.permissions'; $form['#cache']['contexts'][] = 'user.roles:authenticated'; $this->renderer->addCacheableDependency($form, $config); $this->renderer->addCacheableDependency($form, $field_definition->getConfig($entity->bundle()));

Add cache contexts for users

The comment form depends on: - comment field settings- user settings

Add cache tags and contexts from the configuration this form depends on.

#cache: keys‣ #cache ‘keys’ are used for the database row ID.

‣ Most tags are created from ‘contexts’.‣ Some tags are added.

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entity_view:block:bartik_main_menu:[languages:language_interface]=en:[languages:language_url]=en:[route.menu_active_trails:main]=menu_trail.main|:[theme]=bartik:[user.permissions]=120570f7a1954c488d57d2aac1dbc0a48b5072160533431c4ec9f19aa7602e86

#cache contexts:• languages:language_interface• languages:language_url• route.menu_active_trails:main• theme• user.permissions

Added keys:• entity_view• block• bartik_main_menu

Main menu block ‘cid’ taken from table cache_render

#cache bubbling

‣ Cacheability bubbles up during rendering.

‣ Child’s #cache properties are combined into the parent’s #cache properties.

‣ Helper functions in Renderer class.

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Thought process

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Am I rendering something? yes ['#cache']['contexts']

Does the output become outdated

after a certain time?

Does the output vary by

something?

Does the output depend on something?

['#cache']['tags']

['#cache']['max-age']

yes

yes

yes

Demo !

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Demo: Recent content

A simple list of links to recent content.Repo: https://github.com/wizzlern/cacheit

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Provided #cache data

‣ Content entities, configuration, block-, context-, condition-plugins, etc.

‣ Any objects that implement: CacheableDependencyInterface

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interface CacheableDependencyInterface { public function getCacheContexts(); public function getCacheTags(); public function getCacheMaxAge(); }

Renderer::addCacheableDependency($build, $dependency)

Demo: Dynamic Ad

An advertisement block with dynamic content.Repo: https://github.com/wizzlern/cacheit

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Placeholders

‣ Placeholders allow separation of cachable (‘static’) and non-cacheable (‘dynamic’) content.

‣ Lazy builder is a service.

‣ Builder arguments only integer, float, string, boolean.

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if ($display->getComponent('links')) { $build[$id]['links'] = array( '#lazy_builder' => ['comment.lazy_builders:renderLinks', [ $entity->id(), $view_mode, $entity->language()->getId(), !empty($entity->in_preview), ]], '#create_placeholder' => TRUE, ); }

Placeholders

‣ Other placeholder data:‣ css, js header, js footer

‣ Auto placeholdering‣ When #cache properties are below a threshold‣ default: max-age: 0, contexts: ['session', ‘user']‣ Configuration:

renderer.config:auto_placeholder_conditions

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Invalidation process

‣ Cache invalidation per tag‣ +1 ‘invalidation’ in cachetags table‣ Calculate the sum of invalidation of all tags.‣ Compare with ‘checksum’ value in cache_* table.

‣ Stale data remains in the cache_* table until overwritten by new data.

‣ See DatabaseCacheTagsChecksum class

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Debugging

‣ Check cache metadata at page level:‣ http.response.debug_cacheability_headers : true

(in sites/*/services.yml)

‣ Check cache metadata at any level:‣ Renderviz module (still needs love)

‣ Database table cache_render

‣ Test with different user roles !!

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Summary

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Resources

‣ Classes:‣ Drupal\Core\Cache\Cache‣ Drupal\Core\Render\Renderer

‣ Documentation‣ https://drupal.org/developing/api/8/cache‣ http://drupal.org/developing/api/8/render/arrays/

cacheability

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Links

‣ https://events.drupal.org/barcelona2015/sessions/making-drupal-fly-fastest-drupal-ever-here

‣ https://events.drupal.org/barcelona2015/sessions/caching-edge-cdns-everyone

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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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http://wizzlern.nl@wizzlern