How to enable GZIP compression/mod_deflate in Apache

Question

The module mod_deflate in Apache is installed but is not running:

# apachectl -M |grep deflate
 deflate_module (shared)
Syntax OK

If mod_deflate is active, there must be a line Content-Encoding: gzip in the output below:

# curl -I -H 'Accept-Encoding: gzip,deflate' http://example.com/
HTTP/1.1 200 OK
Date: Fri, 25 Sep 2015 00:02:16 GMT
Server: Apache
X-Pingback: http://example.com/xmlrpc.php
X-Powered-By: PleskLin
Connection: close
Content-Type: text/html; charset=UTF-8

As the line is not presented, gzip compression is not active. How to activate it?

Answer

1. Create the file /etc/httpd/conf.d/deflate.conf with the following content on Apache Service node:

   <ifmodule mod_deflate.c>
       AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css text/javascript application/javascript
       DeflateCompressionLevel 8
   </ifmodule>
   

2. Reload web server on Apache Service node:

   [root@pa115apachemysql1 ~]# /etc/init.d/httpd reload
   Reloading httpd:
   

3. Check if compression is active:

   # curl -I -H 'Accept-Encoding: gzip,deflate' http://example.com/
   HTTP/1.1 200 OK
   Date: Fri, 25 Sep 2015 00:04:26 GMT
   Server: Apache
   X-Pingback: http://example.com/xmlrpc.php
   X-Powered-By: PleskLin
   Vary: Accept-Encoding
   Content-Encoding: gzip    <---- this line indicates that compression is active
   Content-Length: 20
   Connection: close
   Content-Type: text/html; charset=UTF-8