Install Varnish Cache for Apache on CentOS

Varnish Cache is a popular caching solution that can be used to speed up the delivery of content on your web server. It works by caching frequently accessed content in memory so that subsequent requests can be served from the cache instead of being processed by the web server. In this article, we will guide you through the process of installing and configuring Varnish Cache for Apache on CentOS.

Install Apache

The first step is to install Apache on your CentOS server. You can do this by running the following command:

sudo yum install -y httpd

Next, you need to configure Apache to work with Varnish. Open the Apache configuration file in your favorite text editor:

sudo nano /etc/httpd/conf/httpd.conf

Find the line that starts with Listen and change it to:

Listen 127.0.0.1:8080

This tells Apache to listen on port 8080 instead of the default port 80. Save and close the file.

Restart and enable Apache

sudo systemctl start httpd.service
sudo systemctl enable httpd.service

Install Varnish Cache

sudo yum install -y epel-release
sudo yum install -y pygpgme yum-utils

To include the Varnish repository, you need to make modifications to the /etc/yum.repos.d/varnish60lts.repo file.

sudo nano /etc/yum.repos.d/varnish60lts.repo

Paste the following lines:

[varnish60lts]

name=varnishcache_varnish60lts

baseurl=https://packagecloud.io/varnishcache/varnish60lts/el/7/x86_64

repo_gpgcheck=1

gpgcheck=0

enabled=1

gpgkey=https://packagecloud.io/varnishcache/varnish60lts/gpgkey

sslverify=1

sslcacert=/etc/pki/tls/certs/ca-bundle.crt

metadata_expire=300

Update the yum cache for the Varnish repo:

sudo yum -q makecache -y --disablerepo='*' --enablerepo='varnish60lts'

To install Varnish on your CentOS server you need to run the following command:

sudo yum install -y varnish
sudo systemctl enable --now varnish

This will install Varnish Cache and all its dependencies on your server.

Configure Varnish Cache

Configure Varnish to listen at port 80, from the default of 6081. Edit varnish.service with nano.

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

Change the line beginning with ExecStart from port 6081 to port 80, then save and close the file. The line should like like this when finished.

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

Save and close the file when you’re done.

Start Varnish

Now that everything is configured, it’s time to start Varnish Cache. You can do this by running the following command:

sudo systemctl daemon-reload

sudo systemctl restart varnish

This will start the Varnish Cache service.

Test Varnish Cache

You can also use the curl command to request a page from your web server:

curl -I http://server-IP

The output should show you whether the request was served from the cache or from the backend server.

Conclusion

You have successfully installed and configured Varnish Cache for Apache on CentOS. By caching frequently accessed content, Varnish Cache can significantly improve the performance of your web server, making it faster and more responsive for your users.