Rendering & caching: a journey through the layers

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.

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