In our checklist for perfect WordPress-Nginx setup, we have a section dedicated to check if page-caching will work in case PHP/MySQL backend crash. Some readers did not like my way of actually shutting down PHP backend for cache-verification.

If you are using Nginx’sfastcgi_cache, then you can useupstream_cache_status variable to test cache for particular URLs without shutting down PHP.

All you need to do is, add a line like below to /etc/nginx/nginx.conf file, in http{..} block:


			add_header rt-Fastcgi-Cache $upstream_cache_status;

Just reload nginx config: service nginx reload

Check HTTP response for any page and you will see something like:


			HTTP/1.1 200 OK
Server: nginx
Date: Fri, 26 Jul 2013 15:38:51 GMT
Content-Type: text/html; charset=UTF-8
Connection: keep-alive
Vary: Accept-Encoding
X-Powered-By: PHP/5.4.17-1~precise+1
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
X-Pingback: http://rtcamp.com/xmlrpc.php
rt-Fastcgi-Cache: HIT

Please note last line. Value next to rt-Fastcgi-Cache indicates fastcgi-cache status.

If you see a MISS, send similar request again and it should get you a HIT.

If you see BYPASS, that means some conditions for skipping cache are met.

Nginx

PREVIOUS

Amazon Elastic Load Balancer and Forwarding Real-IP Nginx

NEXT

Comments

ovidiu

July 26, 2013

Thanks, that neatly answers my question: http://rtcamp.com/groups/wordpress-nginx/forum/topic/caching-issues/

BTW. you have a dead-link in this article, at the bottom of it it says:
“Related: Using for $upstream_cache_status improving cache efficiency” and the link gives a 404 error.
1. Rahul Bansal
  
  August 8, 2013
  
  Thanks. Fixed broken link. 🙂
buzz

September 29, 2013

Dumb question: How do I “check HTTP response for any page”?
1. Rahul Bansal
  
  September 29, 2013
  
  You can use CURL command or an online tool like this – http://web-sniffer.net/
buzz

September 29, 2013

Thanks!
PandaJim

October 30, 2013

I get BYPASS for all pages except homepage. Why? I’ve followed your tutorial to set up fastcgi on LNMP
1. PandaJim
  
  October 30, 2013
  
  My site url looks like: http://domain/index.php/2013/10/postname/
Rahul Bansal

October 30, 2013

Use nginx-helper plugin to remove index.php from permalinks – http://wordpress.org/plugins/nginx-helper/

I think index.php in URL is reason for cache getting BYPASS.

Also, you may need to save your wordpress-permalinks again after activating nginx-helper. Though you don’t need to make any changes in nginx-helper as activating it is enough to remove index.php from permalinks.
1. PandaJim
  
  November 11, 2013
  
  Now I get HIT, but there’s no following like output in the page source:
```



```
  confused.
  1. Rahul Bansal
    
    November 11, 2013
    
    Both are different thing. HIT in curl output is enough to conclude cache is working properly.
    
    If you want to see HTML comments in output, go to nginx-helper plugin settings and turn on “Enable Nginx Timestamp in HTML” option.

Features

Useful Links

Product

Other Products

GoDAM

Subscribe for curated product updates, tips, and announcements.

"*" indicates required fields

Facebook

This field is for validation purposes and should be left unchanged.

Email*