Set maximum / disable custom block cache for anonymous users

Question

I have a little issue regarding my custom block module. The module itself fetches weather data via json-request and the data is shown as a 4-day weather forecast to the user. As the weather should be actualized every day I want to set a "maximum cache time" or even disable caching for the whole block. Right now I would have to flush the cash manually every day.

After a little bit of research to that topic I found out that using 'max-age' in the build() function would do the trick but it does not affect the caching for anonymous users at all.

Using \Drupal::service('page_cache_kill_switch')->trigger(); would disable the cache for a specific page or content-type but I don't want to disable the caching for a whole page at once.

So how can I trigger the caching for my custom-block? Or is there even a way to disable the caching for a certain part of the code e.g. the json-request in my case?

Answer 1

This is a known issue Bubbling of elements' max-age to the page's headers and the page cache.

The Internal Page Cache is designed for database content, which is handled by cache tags. So a workaround would be to add a custom cache tag to the block

$build['#cache']['tags'][] = 'weather_forecast';

which will bubble up to the page level and so you can invalidate both cached items, block and page, in a cron job:

/**
 * Implements hook_cron().
 */
function mymodule_cron() {
  \Drupal\Core\Cache\Cache::invalidateTags(['weather_forecast']);
}

All credit goes to @Berdir: Cache max-age and varnish ESI

Answer 2

Limitations of max-age

Unfortunately, max-age does not work for anonymous users and the Drupal core Page Cache module. For example, see these issues:

• #2352009: [pp-3] Bubbling of elements' max-age to the page's headers and the page cache
• #2449749: Add #cache['downstream-ttl'] to force expiration after a certain time and fix #cache['max-age'] logic by adding #cache['age']
• #2835068: PageCache caching uncacheable responses (violating HTTP/1.0 spec) + D8 intentionally disabling HTTP/1.0 proxies = WTF
• #2951814: Always set X-Drupal-Cache and X-Drupal-Dynamic-Cache headers, even for responses that are not cacheable

Until these (and perhaps other) issues are resolved, beware that setting max-age on a render array included in a page is insufficient to ensure that anonymous users will see a new version after the max-age as elapsed. In the meanwhile, the Cache Control Override contributed module tries to mitigate the problems. You might also have more luck setting a custom cache tag on pages with time-dependent content and invalidating those cache tags manually via hook_cron(). Good luck!

Source: https://www.drupal.org/docs/drupal-apis/cache-api/cache-max-age#s-limitations-of-max-age