How to Cache-Control Headers in Nginx Part 3
Cache-Control Headers in Nginx Part - 3
Caching is an important protocol as per as HTTP and browsing. The basic principle of content caching is to offload repetitive work from the upstream servers. There are specific directives for caching mechanisms and these directives need to be followed by caching servers either be it in the browser or a dedicated cache server. The cache policies are specified by the browsers and dedicated cache servers. The cache mechanism works with the help of cache-control header.
In our previous tutorial, we have covered expire header and some basics of the cache-control header. If you have missed it, you can check it at the following link:
How To Cache-Control In Nginx - Part 1
How To Cache-Contril In Nginx - Part 2
Cache &ndash Control Header types
&bull Cache-control : no-store
&bull Cache-control : no-cache
&bull Cache-control : max-age=0
&bull Cache-control : s-maxage=0
&bull Cache-control : must-revalidate
&bull Pragma : no-cache
In this tutorial, we are going to cover s- maxage
s-maxage
s-maxage is specifically for intermediate cache server which means the public cache will store the cache for the seconds mentioned in that directive. For example, if a webserver sends its configuration with both the max-age and s-maxage directive in it, you can see both the headers in it.
s-maxage is applicable only for intermediate cache (public cache).
* Private Cache => Client browser Cache
* Public Cache => A dedicated server which is maintained only for storing Cache
Cache- Controlling
Let us do a simple Virtual Host configuration with maxage header. Open your configuration file.
[root@linuxhelp ~]# cd /etc/nginx/conf.d/
[root@linuxhelp conf.d]# vim vir.conf
Make sure you make the following modifications.
server {
server_name www.linuxhelp1.com
location / {
root /usr/share/nginx/html
index index.html index.htm
add_header Cache-Control max-age=120
}
}
Save and exit it
You shall now restart your nginx service by making use of
[root@linuxhelp html]# systemctl restart nginx
Now execute curl command and also check it in the browser
[root@linuxhelp html]# curl -I http://www.linuxhelp1.com/web1.html
HTTP/1.1 200 OK
Server: nginx/1.12.2
Date: Wed, 07 Feb 2018 12:34:19 GMT
Content-Type: text/html
Content-Length: 20
Last-Modified: Wed, 07 Feb 2018 12:33:50 GMT
Connection: keep-alive
ETag: " 5a7af22e-14"
Cache-Control: max-age=120
Accept-Ranges: bytes
We can make the modifications now, so assign s-max age in the configuration file. Open the file.
[root@linuxhelp ~]# cd /etc/nginx/conf.d/
[root@linuxhelp conf.d]# vim vir.conf
And make the following changes.
server {
server_name www.linuxhelp1.com
location / {
root /usr/share/nginx/html
index index.html index.htm
# add_header Cache-Control max-age=120
add_header Cache-Control s-maxage=200
}
}
Once it is done, execute curl command
[root@linuxhelp conf.d]# curl -I http://www.linuxhelp1.com
HTTP/1.1 200 OK
Server: nginx/1.12.2
Date: Thu, 15 Feb 2018 12:01:08 GMT
Content-Type: text/html
Content-Length: 42
Last-Modified: Thu, 15 Feb 2018 11:59:30 GMT
Connection: keep-alive
ETag: " 5a857622-2a"
Cache-Control: s-maxage=200
Accept-Ranges: bytes
You will notice that Cache-Control is configured.
You can now restart the nginx service.
[root@linuxhelp conf.d]# systemctl restart nginx
Next, assign both the headers inside the configuration file. So, open the configuration file by making use of the following commands. And make the below configuration.
[root@linuxhelp ~]# cd /etc/nginx/conf.d/
[root@linuxhelp conf.d]# vim vir.conf
server {
server_name www.linuxhelp1.com
location / {
root /usr/share/nginx/html
index index.html index.htm
add_header Cache-Control max-age=120
add_header Cache-Control s-maxage=200
}
}
Check for the syntax now.
[root@linuxhelp conf.d]# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
Again, restart the nginx service.
[root@linuxhelp conf.d]# systemctl restart nginx
You should now execute the curl command again.
[root@linuxhelp conf.d]# curl -I http://www.linuxhelp1.com
You will notice the Cache-Control configuration.
HTTP/1.1 200 OK
Server: nginx/1.12.2
Date: Thu, 15 Feb 2018 12:02:02 GMT
Content-Type: text/html
Content-Length: 42
Last-Modified: Thu, 15 Feb 2018 11:59:30 GMT
Connection: keep-alive
ETag: " 5a857622-2a"
Cache-Control: max-age=120
Cache-Control: s-maxage=200
Accept-Ranges: bytes
This is how both the Cache-control headers been used in the nginx configuration file.
The major difference is only when max-age is specified both the private and public cache gets the cache value assigned in the max-age directive.
After assigning both the values if you check in the browser only max-age gets displayed
This is because it shows only (private) that is client’ s browser cache. With this, the tutorial comes to an end.
# nginx -t