Drupal's Cache API provides mechanisms for storing and retrieving data efficiently to improve performance, and its use in outputting render arrays ensures that content is cached and reused, reducing server load and response times. This course covers the Cache API's key components, including cache keys, tags, contexts, and max-age, and how they are used to define the cacheability of content. You will also learn how to add cache metadata to render arrays to improve performance and ensure proper cache invalidation. Additionally, the course will explore the use of lazy builders and placeholders to handle highly dynamic content efficiently.
Key topics
- Overview of the Cache API and its components
- Adding cache metadata to render arrays
- Using cache keys, tags, contexts, and max-age to define cacheability
- Implementing lazy builders and placeholders for dynamic content
Many of the processes that Drupal performs when responding to a request are cached in order to increase performance. Creating the HTML for the page that a user sees or the JSON response to a REST request can require thousands of operations. Some operations are time consuming, memory heavy, CPU intense, or all 3. By performing the operation once, and then caching the result for next time, subsequent requests can be fulfilled faster. In order to make it easier to store, retrieve, and invalidate cached data, Drupal provides cache-related services you can use in your code. Drupal also enables you to provide information about the cacheability of data to the Render API to improve the performance of page rendering.
In this tutorial we'll:
- Cover the terms and concepts you should be familiar with when working with the Cache API
- Point to additional resources for more information about how to perform specific tasks with the Cache API
By the end of this tutorial, you should be able to define the concepts of bubbling and cache invalidation, and know how cache keys, tags, context, and max-age are used to provide cacheability metadata for items.
The individual items that make up the content of a page impact the cacheability of that page. In order for Drupal's cache and external caches to better understand how the content varies on a page, module developers use the #cache render element property. The #cache property defines cacheability metadata for individual elements in a render array.
Additionally, these Render API elements can become fairly complex. The calculation of what the final HTML output should look like often involves looking up content in the database, checking multiple conditions, maybe querying an external API, and various other tasks. This can cause turning a render array into HTML to become quite expensive. In order to speed up this process, the Render API will cache the generated HTML for each element and reuse it on future requests whenever possible -- but only if you tell it to do so.
In this tutorial, we'll look at:
- How render caching impacts the performance of a page
- Defining the cacheability of an item with cache tags, cache contexts, and cache max-age
- Examples of using the
#cacheproperty in a render array
By the end of this tutorial you should know how, and when, to use the #cache property when defining render arrays.
The Render API is capable of detecting poorly-cacheable (highly dynamic) parts of a page and rendering them later using a process called auto-placeholdering. This works by using #lazy_builder callbacks to lazy load certain very dynamic subtrees of a render array. The place in the array where that very dynamic content would appear is first assigned a placeholder. At the very last moment it is replaced with the actual content.
This allows Drupal to do things like cache the overall page in the Dynamic Page Cache despite parts of the page being too dynamic to be worth caching. It also allows the Render API to assemble a page using cache fragments combined with non-cacheable elements.
In this tutorial we'll:
- Discuss what lazy builders are and how they work in conjunction with placeholders to speed up the rendering pipeline
- Cover some common gotchas for lazy builders
- Look at some example code that implements a lazy builder callback
By the end of this tutorial, you should know how and when to use the #lazy_builder property of a render array and how Drupal uses placeholders to increase the cacheability of content and speed up the rendering process.
