What is Varnish Cache?
As you know about Cache, it enhances the loading speed by saving web pages, cookies and other data. It saves into memory the requested data and provide faster results. Because of its faster response, it is also used in Linux like Centos to provide faster results. It is also called caching HTTP reverse proxy which is a leading web application accelerator, capturing the visits and boost upon delivery on again request. It saves the web servers time by providing them the same data as saved earlier. Hence, in this tutorial we are going to learn how you can install and configure Varnish Cache 6 on CentOS 8 / RHEL 8.
Step 1: Update System
Make sure your system is up-to-date.
sudo dnf -y update
Step 2: Install Varnish Cache 6 on CentOS 8 / RHEL 8
You can use the following command to install varnish cache on CentOS / RHEL 8.
sudo dnf install @varnish
Allow to continue with the installation process by pressing y key.
If you want to see more information on installed package you can type the following command.
rpm -qi varnish
Important things to Remember:
- Main configuration file of Varnish can be found in /etc/varnish/default.vcl
- Secret file of Varnish is in /etc/varnish/secret
- Cashe executable binary is found in /usr/sbin/varnishd
- Systemd unit file is in /lib/systemd/system/varnish.service
Step 3: Start and Enable Varnish Cache Services
Use the following command to start & enable Varnish Cache services.
sudo systemctl enable --now varnish
Make sure status is working properly
systemctl status varnish
Step 4: Configure Varnish Cache for Nginx/Apache Web Server
As Varnish sits in front of a web server as a caching HTTP Reverse Proxy, so it speeds up web servers.
In this tutorial we are using Nginx/Apache HTTPD server but you can use your favourite one.
For Apache
sudo dnf -y install @httpd
For Nginx
sudo dnf -y install @nginx
1. Configure Nginx with Varnish
By default, TCP port 80 is being used by Nginx, change it to listen to 8080 port because Varnish Cache will use port 80.
sudo vi /etc/nginx/nginx.conf
For Virtual Hosting feature, edit the relevant confiuguration file,
sudo vi /etc/nginx/conf.d/mysite.conf
After it, restart Nginx
sudo systemctl restart nginx
Double-check your settings
ss -tunelp | grep 8080
2. Configure Apache with Varnish
For Apache web server, make sure to set listen port to 8080.
sudo vi /etc/httpd/conf/httpd.conf
After it, restart Apache.
sudo systemctl restart httpd
3. Configure Varnish Cache Server
Set Listen port for Varnish Cache to 80.
sudo vi /etc/systemd/system/multi-user.target.wants/varnish.service
Edit the line starting with ExecStart, and change from:
ExectStart=/usr/sbin/varnishd -a :6081 -f /etc/varnish/default.vcl -s malloc,256m
To:
ExectStart=/usr/sbin/varnishd -a :80 -f /etc/varnish/default.vcl -s malloc,256m
Now, restart Varnish systemd services.
sudo systemctl daemon-reload
sudo systemctl restart varnish
Make sure that Varnish is listening the correct port.
sudo systemctl status varnish
Also make sure that Nginx/Apache server is configured as a back-end server for Varnish proxy.
sudo vi /etc/varnish/default.vcl
Look port 8080 is configured on Apache/Nginx web server.
Your configuration will look like this for multiple back-ends,
backend default {
.host = "127.0.0.1";
.port = "8080";
}
backend java {
.host = "127.0.0.1";
.port = "8000";
}
But we’ll need to tell Varnish to where send the difference URL using vcl_recv. For example our java application should handle URL beginning with /java/
sub vcl_recv {
if (req.url ~ "^/java/") {
set req.backend_hint = java;
} else {
set req.backend_hint = default;
}
}
You can see more ones on using Multiple backends.
Step 5: Testing Varnish Cache on Nginx/Apache
After all, verify Varnish Cache working by testing it with Apache/Nginx service with the curl command:
curl -I http://localhost
It will provide you HTTP header information.
If you run this command again, it will show you that Varnish Cached Response (Note that Age header):
This will work same for other valid domain names with DNS record set.
curl -I https://osradar.com
We’ve installed & configured Varnish Cache on CentOS 8 / RHEL 8 for Nginx and Apache Web Server.
Visit the Varnish Getting Started and The Varnish Users Guide pages to learn more about configuring & optimizing Varnish.
