Tuesday, April 23, 2013

Cleaning cache for Apache by htcacheclean

Detecting apache cache problem, cleaning cache for apache by htcacheclean.
good pages: page1, page2, page3.

My case:
in apache config /www/etc/apache/adm/virt.serv/10_my-service.cfg:

CacheRoot /www/cache/my-service
CacheDirLevels 2
CacheDirLength 1
CacheDefaultExpire 3600
CacheIgnoreCacheControl On
CacheEnable disk /my-service/

I get different content:
wget https://server.com/my-service/css/layout.css
wget https://test-server.com/my-service/css/layout.css

as HTTP Header have value:
Cache-Control: max-age=31556926, must-revalidate 
How to get this in Firebug addon of Firefox:

Or you can do this from terminal :
06:20 PM ~ $ curl -I https://server.com/my-service/css/layout.css
HTTP/1.1 200 OK
Date: Wed, 24 Apr 2013 01:20:08 GMT
Server: Apache/2.2.19 (FreeBSD)
Expires: Thu, 24 Apr 2014 07:08:54 GMT
Cache-Control: max-age=31556926, must-revalidate
Last-Modified: Mon, 22 Apr 2013 17:32:10 GMT
Content-Length: 36490
Connection: close
Content-Type: text/css
Set-Cookie: Coyote-2-4a7446e9=c0a89971:0; path=/

So caching could be adjusted on Tomcat side, after then on Apache side(CacheDefaultExpire and "CacheEnable disk /my-service/"), and then kept by user's Browser(Cache-Control: max-age). 

Cache could be adjusted in tomcat side in Spring config (28800 = 8 hour):
<mvc:resources mapping="/css/**" location="/css/" cache-period="28800" />

So after each Tomcat rollout we have to do:
htcacheclean -p/www/cache/my-service -l1K -v

if you have problem on apache clear cache like "An error occurred, cache cleaning aborted."
be sure you  /www/cache/my-service/ is created and "chown apache /www/cache/my-service/", "apache" username is taken from "ps -ef| grep http" as on Freebsd it is "www". Also be sure you launch htcacheclean under right user.


  1. Can we run htcacacheclean via a cron job , Is there any performance impact from apache

  2. I did not test this, we need such cleaning only after release of new content. In all other cases it is not required.