Problems activating Object Cache

Tagged: Object Cache, Redis

Viewing 9 posts - 1 through 9 (of 9 total)

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May 1, 2025 at 10:29 am #156960
Gregor
Guest
Hi, I am getting this exact error message when I activate the Object Cache. I don’t have a clue how this happened:
The Object Cache add-in file object-cache.php is not a W3 Total Cache drop-in. Remove it or disable Object Caching. <input type="button" class="button" value="Yes, remove it for me" onclick="w3tc_beforeupload_unbind(); document.location.href='https://hanfjournal.de/wp-admin/admin.php?page=w3tc_general&w3tc_default_remove_add_in=objectcache&_wpnonce=93a8e27d2d';" />
It’s a fresh install, all settings default. However W3 Cache was installed before some time ago and then removed.
Second problem: When I test Redis on the advanced object cache configuration page, it always fails. The server has Redis activated, I can set this in the hosting config tool, but W3 seems to be unable to connect. What can I do?
May 1, 2025 at 11:25 am #156981
Marko Vasiljevic
Keymaster
Hello Gregor,
Thank you for reaching out, and I am happy to help!
As the notification suggests, the drop-in file that is detected is not a W3 Total Cache drop-in.
Please try to manually delete the file from the wp-content folder and re-enable Object Caching.
As for the Redis, if this is not fixed when the mentioned file is deleted, please check with your hosting provider if you can restart the Redis
Let me know if this helps!
May 2, 2025 at 12:49 pm #157009
Gregor
Guest
Thanks! Deleting this file has helped, error message gone. Also with help of my hosters support, I found out that first, Redis was not not fully enabled yet (had to be specifically enabled on that domain), and second, in W3 cache advanced settings I had to enter as Redis hostname exactly this: /run/redis/redis.sock
W3 says “Test passed.” and I think it’s working great.
May 2, 2025 at 12:49 pm #157015
Gregor
Guest
Update: it seemed like it was working, but then I noticed that trying to access the site from another browser or device (not logged in as admin) always resulted in a critical WP error. Turning off object cache, it is working again. I also activated page cache with Redis, no problems with that.
I caught these error messages when object cache with Redis was enabled:
Fatal error: Uncaught RedisException: OOM command not allowed when used memory > ‘maxmemory’. in /web/wp-content/plugins/w3-total-cache/Cache_Redis.php:199
Stack trace:
#0 /web/wp-content/plugins/w3-total-cache/Cache_Redis.php(199): Redis->setex()
#1 /web/wp-content/plugins/w3-total-cache/PgCache_ContentGrabber.php(360): W3TC\Cache_Redis->get_with_old()
#2 /web/wp-content/plugins/w3-total-cache/PgCache_ContentGrabber.php(288): W3TC\PgCache_ContentGrabber->_extract_cached_page()
#3 /web/wp-content/advanced-cache.php(42): W3TC\PgCache_ContentGrabber->process()
#4 /web/wp-settings.php(99): include(‘/web/…’)
#5 /web/wp-config.php(109): require_once(‘/web/…’)
#6 /web/wp-load.php(50): require_once(‘/web/…’)
#7 /web/wp-blog-header.php(13): require_once(‘/web/…’)
#8 /web/index.php(17): require(‘/web/…’)
#9 {main} thrown in /web/wp-content/plugins/w3-total-cache/Cache_Redis.php on line 199
Fatal error: Uncaught RedisException: OOM command not allowed when used memory > ‘maxmemory’. in /web/wp-content/plugins/w3-total-cache/Cache_Redis.php:150
Stack trace:
#0 /web/wp-content/plugins/w3-total-cache/Cache_Redis.php(150): Redis->setex()
#1 /web/wp-content/plugins/w3-total-cache/ObjectCache_WpObjectCache_Regular.php(388): W3TC\Cache_Redis->set()
#2 /web/wp-content/plugins/w3-total-cache/ObjectCache_WpObjectCache_Regular.php(532): W3TC\ObjectCache_WpObjectCache_Regular->set()
#3 /web/wp-content/plugins/w3-total-cache/ObjectCache_WpObjectCache.php(196): W3TC\ObjectCache_WpObjectCache_Regular->add()
#4 /web/wp-content/object-cache.php(206): W3TC\ObjectCache_WpObjectCache->add()
#5 /web/wp-includes/option.php(650): wp_cache_add()
#6 /web/wp-includes/option.php(164): wp_load_alloptions()
#7 /web/wp-includes/default-constants.php(176): get_option()
#8 /web/wp-settings.php(444): wp_plugin_directory_constants()
#9 /web/wp-config.php(109): require_once(‘/web/…’)
#10 /web/wp-load.php(50): require_once(‘/web/…’)
#11 /web/wp-blog-header.php(13): require_once(‘/web/…’)
#12 /web/index.php(17): require(‘/web/…’)
#13 {main} thrown in /web/wp-content/plugins/w3-total-cache/Cache_Redis.php on line 150
May 2, 2025 at 12:52 pm #157024
Marko Vasiljevic
Keymaster
Hello Gregor,
The maxmemory is a Redis configuration setting.
Can you please check Redis configuration on your server and check the maxmemory
Thanks!
May 2, 2025 at 12:52 pm #157025
Marko Vasiljevic
Keymaster
Hello Gregor,
The maxmemory is a Redis configuration setting.
Can you please check Redis configuration on your server and check the maxmemory
Thanks!
May 7, 2025 at 12:10 pm #157188
Gregor
Guest
Thanks, problem solved! I did not understand that the error message actually just said “not enough memory” 🙂
The default setting was 512MB which I raised to 4096MB because the server has plenty of RAM.
May 7, 2025 at 12:10 pm #157232
Gregor
Guest
Correction: The Redis memory was set 64MB when the error occurred. With 512MB and higher the error was gone.
Thank you!
May 7, 2025 at 12:11 pm #157236
Marko Vasiljevic
Keymaster
Hello Gregor,
You are most welcome!
We would really appreciate it if you could take a minute and post a review here. This will help us to continue offering a top-notch product to users.
Thanks!
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