Below you find my notes to install collectd on CentOS 7

 yum install epel-release
 yum install -y collectd collectd-rrdtool rrdtool collectd-web httpd
 yum search collectd
 yum -y install collectd-disk collectd-virt # you may skip that step
 systemctl enable httpd collectd
 cat /etc/httpd/conf.d/collectd.conf 
 sed -i 's/# Require all granted/Require all granted/g;s/Require local/# Require local/g' /etc/httpd/conf.d/collectd.conf 
 systemctl restart httpd collectd

Now, you can access collectd by pointing to: http://servername/collectd/bin/index.cgi