Custom block is still caching for anonymous users despite getCacheMaxAge() being set to 0 and can't figure out why

Question

I have a custom Drupal 8 block with class with build() and getCacheMaxAge() functions. getCacheMaxAge() is set to 0 but it is still being cached for anonymous users.

If I put debug code in the build() function I can see it being called when I'm logged in but not for anonymous users.

My code is below. We do have Memcached installed. Would that be causing the issue?

The only other caching modules are core.

<?php
class HeaderPhone extends BlockBase {
  /**
   * {@inheritdoc}
   */
  public function build() {

    $info = geo_location_blocks_get_region();
    $region = $info['region'];
    $tid = $info['tid'];

    return array(
        '#theme' => 'geo_location_header_phone',
        '#region' => $region,
        '#view' => views_embed_view('locations', 'block_3', $tid),
      
    );
  }

  /**
   * @return int
  */
  public function getCacheMaxAge() {
    return 0;
  }
}?>

  

Answer 1

Setting cache max-age to 0 doesn't work if you still have the core module Internal Page Cache enabled.

Read the documentation why you probably want to disable this module or deliver the block with a different method:

Websites that serve personalized content to anonymous users (dynamic, per-session, e.g. a shopping cart) will want to disable the Internal Page Cache module. This module assumes pages are identical for all anonymous users. Those websites can still take advantage of the Dynamic Page Cache module though, or can alternatively do their personalization using JavaScript + AJAX.

https://www.drupal.org/docs/administering-a-drupal-site/internal-page-cache