How to Install Varnish Cache with Apache on CentOS 8

Caching is the process of storing copies of files in a cache so that future requests for that file can be accessed more quickly. Varnish is a free, open-source, powerful HTTP engine and reverse HTTP proxy used by more than 3.4 million websites. It stores the incoming page requests in memory and serves the same page request directly from Varnish cache instead of going straight to the web server.

This will speed up the performance of your website significantly. Varnish has its own configuration language (VCL) to write policies on incoming requests such as back-end servers, ACLs, responses, and more.

In this tutorial, we will learn how to set up Varnish caching with Apache on CentOS 8. We will set up Apache to listen on port 8080 and work as a backend server, then configure Varnish to listen on default HTTP port 80.

Step 1 – Install Varnish Cache

By default, the Varnish package is available in the CentOS 8 system. You can install it by just running the following command:

dnf update -y
dnf install varnish -y

After installing Varnish, start the Varnish service and enable it to start after system reboot with the following command:

systemctl start varnish
systemctl enable varnish

Next, verify the status of Varnish with the following command:

systemctl status varnish

You should get the following output:

By default, Varnish listens on port 6081. You can verify it using the following command:

netstat -ltnp | grep 6081

You should get the following output:

tcp        0      0 0.0.0.0:6081            0.0.0.0:*               LISTEN      1508/varnishd
tcp6       0      0 :::6081                 :::*                    LISTEN      1508/varnishd

Step 2 – Install and Configure Apache

Next, you will need to install the Apache webserver and configure it to work with the Varnish cache.

First, install the Apache server with the following command:

dnf install httpd -y

After installing the Apache webserver, you will need to change the Apache web server listening port from 80 to 8080.

You can do it by editing the file /etc/httpd/conf/httpd.conf.

nano /etc/httpd/conf/httpd.conf

Find the following line:

Listen 80

And replace it with the following line:

Listen 8080

Save and close the file, then start the Apache service and enable it to start after system reboot:

systemctl start httpd
systemctl enable httpd

Next, copy the sample index.html page to the Apache default document root directory:

cp /usr/share/httpd/noindex/index.html.en-US /var/www/html/index.html

Note: If you are using Virtual hosting, then configure the relevant configuration file.

Step 3 – Configure Varnish to Work with Apache

By default, Varnish is configured to listen on port 6081, so you will need to configure it to listen on port 80. You can configure it by editing varnish.service configuration file:

nano /usr/lib/systemd/system/varnish.service

Find the following line:

ExecStart=/usr/sbin/varnishd -a :6081 -f /etc/varnish/default.vcl -s malloc,256m

And replace it with the following line:

ExecStart=/usr/sbin/varnishd -a :80 -f/etc/varnish/default.vcl -s malloc,256m

Save and close the file, then reload the systemd daemon with the following command:

systemctl daemon-reload

Next, restart Varnish service to apply the changes:

systemctl restart varnish

Step 4 – Configure Apache as a Backend Server for Varnish

Next, you will need to configure Apache as a backend server for the Varnish proxy.

You can configure it by editing the file /etc/varnish/default.vcl:

nano /etc/varnish/default.vcl

Uncomment the following lines if commented:

backend default {
.host = "127.0.0.1";
.port = "8080";
}

Save and close the file when you are finished.

Note: Change the line 127.0.0.1 with your Apache server IP address if your Apache server resides on the other host. Change the port 8080 with a port number of your Apache server.

Step 5 – Verify Varnish Cache

At this point, the Varnish cache is configured to work with the Apache webserver. It’s time to test whether caching is working or not.

You can test it using the curl command:

curl -I http://your-server-ip

You should get the HTTP header information in the following output:

Next, run the command again:

curl -I http://your-server-ip

You should get the Varnish cached response in the Age header:

You can also test the varnish cache using varnishlog command with curl command to view Varnish activity as it happens:

varnishlog

You should get an output similar to the following:

Conclusion

Congratulations! You have successfully installed and configured Varnish cache with Apache web server on CentOS 8. Your website should now load faster because Varnish will retrieve the most frequently requested content from the cache memory. Try out Varnish on dedicated server hosting from Atlantic.Net!