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Designate provides DNS as a Service in OpenStack

Central Register

Article from ADMIN 37/2017

By Martin Loschwitz

The management of DNS entries works fundamentally differently for clouds than for classic setups; OpenStack Designate is a meaningful and well-functioning DNS as a Service implementation.

DNS is normally one of the first services set up for new infrastructures in the data center; otherwise, it is hardly possible to use the other computers. Many people often only realize how crucial DNS is when it stops working, such as when a website cannot be accessed because the responsible DNS server has crashed. In short: DNS is a fundamental prerequisite for virtually all other services an admin sets up.

The topic of DNS has several dimensions: On the one hand, computers must be able to resolve hostnames to communicate with other computers within and outside the setup. On the other hand, the management of your own DNS entries is done in the appropriate DNS servers: A website that can only be accessed via IP address is rarely desirable; a web address of the expected structure is preferred (e.g., www.example.com ). To that end, a corresponding A record (or AAAA [quad-A] record for IPv6) must be stored for a domain, and a corresponding PTR record (which refers to the A record) must be created in the DNS file for the respective address space.

DNS management for VMs in clouds must be deeply integrated into the cloud itself. The software used must create suitable DNS entries for A/AAAA and PTR records when creating virtual instances, as can be well demonstrated by using the concrete example of OpenStack. The OpenStack component that takes care of the management of DNS entries is called Designate. In this article, I explain what the Designate architecture looks like and at which points Designate becomes involved in setups to attain functioning DNS entries for virtual cloud instances. The goal is DNS as a Service (DNSaaS).

Conventional Is Simple

Classic setups planned from the beginning make DNS easy to address. In such setups it is possible to incorporate both the infrastructure required for DNS and the specific entries for individual hosts and IPs; therefore, it is obvious

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