Fastcgi_cache, Mobile theme, Purge

Hello there,

I am using Jetpack mobile theme, so I want different cache for each version, desktop and mobile. Not a problem, just need to first identify if user-agent is mobile, set a variable (mobile=1) and attach this variable to the cache_key.

fastcgi_cache_key $scheme$request_method$host$request_uri$mobile_request";

We then use the server block to identify mobile visitors.

set $mobile_request 0;  
if ($http_user_agent ~* "(android|iphone)") {  
set $mobile_request 1;  

Thats not all user agents! This is just a sample

Everything works fine I have two cache versions one for mobile theme and another for desktop, all on same domain. Problem is with cache purge. If I append the $mobile_request variable to the purge cache key identifier, only the version of my useragent (desktop) gets purged. If I leave it empty I get a 404 - cache not fond / not cached on log.

How can I purge both versions?

Best regards!


This is known limitation of nginx's purge module -

One idea was to use wildcards but it has limitation from nginx-core -

Fixing this issue is on our list as well.

We will try to see what we can do using

Thanks alot.
I am using nginx-helper plugin and it works great, except for the wildcard purge.

I can one see a hardcoded solution and that I cannot use. So I guess I’ll have to wait on nginx side (wildcards) for that one.

Best regards.

From Nginx side, we shouldn’t wait for any wildcard things. Its something very complex and not inline with md5-hashing.

First workaround we are planning is: in nginx-helper give a textarea where you can specify additional header per line (in your case you will give 2 lines for 2 user-agents sample - one for desktop and one for mobile).

Then nginx-helper will initiate a normal purge request for every-line in textarea. For this to be efficient, we need to add some kind of job-queue (e.g. redis)

Second approach is: explore possibilities with memcahce. If memcache keys can support wildcards, regex, etc, the use memcache-based store rather than fastcgi-cache.

Both will need a lot of work and testing. That is why it will take time!

In meantime, we use “Purge Cache” option integrated in wordpress admin-bar to quickly flush entire fastcgi-cache.

Thanks Dominique, I used the block slightly different at this stage just to skip caching for mobile users.

Where should the fastcgi_cache_key $scheme$request_method$host$request_uri$mobile_request”; be set? just in the server block as well?

I’m keen to keep modifications to a minimum to reduce chance of issues with easyengine updates etc.


Hmm just realised I’ve been doing double caching, I had been caching with W3 Total Cache page cache as well as fastcgi. For some reason I thought the files generated by W3TC were used by fastcgi. Anyway, have disabled page cache on W3TC and think I can see where the cache key needs to be set.

Hi Rahul, this topic is several years old. Has nginx-helper been updated to clear all caches including mobile versus other like in the original post?


No. But we are close with new redis full-page cache option (--wpredis). Redis has wildcard support. We are planning to provide a wordpress hooks/settings which people can use to provide additional purge URL patterns.

Awesome, does Redis support multiple caches like described in the very first post of this thread?


Yep. Redis and Fastcgi-cache supports similar caching rules.

Only difference is - redis cache doesn’t hash keys so we can use wildcard directly. Fastcgi-cache uses hashing so wildcard purge cannot be done directly or efficiently or both!

Nginx-plus (paid) version has support for wildcard Fastcgi-cache purge in case you like to have a look at it -

Thanks Rahul, you might remember I have been struggling with this issue for some time (Nginx fastcgi_cache and Wordpress wp_is_mobile function - not showing correct page versions to correct user devices) so stumbling upon this thread and finding the answer was quite easy to implement was great. I will do some searching myself, but do you know of any good guides for implementing the multiple caches using redis/WPredis through Easy Engine? Thanks!

hi is there any update on this issue? or not how can i purge manually mobile cache? ee clean --all doesn’t help.

see How to - Fastcgi_cache & Desktop with Mobile versions - Purging with GET Requests

Does anyone know if the caching issues in this thread (mobile versus non-mobile) are also present when using redis instead of fastcgi?


I need a solution to separate the cache from the desktop with the mobile cache. Can someone help me?

see first post in this thread