Rendering & caching: a journey through the layers

published on November 6, 2017

The Drupal render pipeline and its caching capabilities have been the subject of quite a few talks of mine and of multiple writings. But all of those were very technical, very precise.

Over the past year and a half I’d heard multiple times there was a need for a more pragmatic talk, where only high-level principles are explained, and it is demonstrated how to step through the various layers with a debugger. So I set out to do just that.

I figured it made sense to spend 10–15 minutes explaining (using a hand-drawn diagram that I spent a lot of time tweaking) and spend the rest of the time stepping through things live. Yes, this was frightening. Yes, there were last-minute problems (my IDE suddenly didn’t allow font size scaling …), but it seems overall people were very satisfied :)

Have you seen and heard of Render API (with its render caching, lazy builders and render pipeline), Cache API (and its cache tags & contexts), Dynamic Page Cache, Page Cache and BigPipe? Have you cursed them, wondered about them, been confused by them?

I will show you three typical use cases:

  1. An uncacheable block
  2. A personalized block
  3. A cacheable block that you can see if you have a certain permission and that should update whenever some entity is updated

… and for each, will take you on the journey through the various layers: from rendering to render caching, on to Dynamic Page Cache and eventually Page Cache … or BigPipe.

Coming out of this session, you should have a concrete understanding of how these various layers cooperate, how you as a Drupal developer can use them to your advantage, and how you can test that it’s behaving correctly.

I’m a maintainer of Dynamic Page Cache and BigPipe, and an effective co-maintainer of Render API, Cache API and Page Cache.


Drupalcon Vienna
Vienna, Austria
Sep 28 2017 - 14:15
60 minutes
Extra information: 


Attendees: 200

Evalutations: 4.6/5

Thanks for the explanation. Your sketches about the rendering process and how dynamic cache, page cache and big pipe work together ; are awesome. It is very clear no for me.

Best session for me on DC. Good examples, loved the live demo, these live demo’s are much more helpful to me as a developer then static slides. General comments, not related to the speaker. The venue was to small for this talk and should have been on a larger stage. Also the location next to the exhibition stands made it a bit noisy when sitting in the back.

Great presentation! I really liked the hand-drawn figure and live demo, they made it really easy to understand and follow. The speaking was calm but engaging. It was great that you were so flexible on the audience feedback.