Page cache isn't invalidated

Looking at the cache_page table, the problem is obvious: all pages have expire set to -1.

My cache metadata was not properly output by Twig.

After that page cache got disabled completely. How can I debug where in the render process max-age is set in a way that makes all pages uncachable?

I found debugging stuff like this extremely hard. I had some success going to "lib/Drupal/Core/Cache/CacheableMetadata.php" and e.g. doing a backtrace in merge() when an unwanted max-age:0 is about to get merged in.

Besides that, I still think this issue is very valid. This module currently only fixes the fact that a default Drupal installation doesnt properly bubble the Max-Age to the Cache-Control HTTP header. It doesnt do anything about the fact that the page cache doesnt support time-based expiration *at all*. Of course, I could write another module for this. But I think it might make sense to integrate it here, so we don't get to a point where we require a whole library of cache fixing modules to get a decent working caching mechanism in Drupal...

Ah. I see, I'm wrong. Page Cache seems to use $expire in core/modules/page_cache/src/StackMiddleware/PageCache.php, storeResponse. But I also found that only -1 ends up in the cache_page table. Weird.

Hello,

The issue here is that PageCache::storeResponse() uses the Expires header but not Cache-Control to invalidate the page cache.
The attached patch helps workaround this problem.

I just noticed that #2962699 contains a similar patch.

Here is a reroll for 2.0.0-rc2.

Rerolled for 8.x-1.x.

Hi,

Thanks for the reroll on 2.0.0-rc2. I use this patch now instead of #2962699-5: Expires header not set → for the version 8.x-1.x.

cache_control_override needs to take global max-age into account.

Here is the patch from MR for Composer usage.

We should probably decide which patch to keep between 🐛 Expires header not set Needs review and 💬 Page cache isn't invalidated Needs review .

MR rebased for version 2.0.1