DNS¶

New in version 0.3.

Terraform lets you configure DNS for your instances. The DNS provider is loosely coupled from the server provider, so you could for example use the dnsimple provider for either OpenStack or AWS hosts, or use the Google Cloud DNS provider for DigitalOcean hosts.

Providers¶

These are the supported DNS providers:

DNS Records and Configuration¶

The providers create a uniform set of DNS A records:

{short-name}-control-{nn}.node{subdomain}.{domain}
{short-name}-edge-{nn}.node{subdomain}.{domain}
{short-name}-worker-{nnn}.node{subdomain}.{domain}
{control}{subdomain}.{domain}
*.{subdomain}.{domain}

For example, with short-name=mantl, domain=example.com, a blank subdomain, 3 control nodes, 4 worker nodes, 2 Kubernetes worker nodes, and 2 edge nodes, that will give us these DNS records:

mantl-control-01.node.example.com
mantl-control-02.node.example.com
mantl-control-03.node.example.com
mantl-worker-001.node.example.com
mantl-worker-002.node.example.com
mantl-worker-003.node.example.com
mantl-worker-004.node.example.com
mantl-kubeworker-001.node.example.com
mantl-kubeworker-002.node.example.com
mantl-edge-01.node.example.com
mantl-edge-02.node.example.com
control.example.com (pointing to control 1)
control.example.com (pointing to control 2)
control.example.com (pointing to control 3)
*.example.com (pointing to edge node load balancer)

If you don’t want the DNS records hanging off the apex, you can specify the subdomain parameter to the DNS providers, which will be inserted in the records just before the apex. For example, if subdomain=.mantl in the previous config, the wildcard records would be *.mantl.example.com.

Warning

Due to a limitation in Terraform’s string support, the subdomain must begin with a period (for example .mantl).

The node records are intended to be used to access each node individually for maintenance. You can access the frontend web components of the Mantl cluster through control.example.com, which will direct you to the rest of the stack.

You can use the wildcard records for load-balanced access to any app in Marathon. For example, if you have an app named test running in Marathon, you can access it at test.example.com. Please see the Traefik configuration for more details.

Configuration¶

A good way to configure DNS is to move the values common to your cloud config and DNS config into separate variables. You can do that like this:

variable control_count { default = 3 }
variable worker_count { default = 2 }
variable kubeworker_count { default = 2 }
variable edge_count { default = 2 }
variable short_name { default = "mantl" }

Then use those variables in the module like this:

module "dns" {
  source = "./terraform/cloudflare"

  control_count = "${var.control_count}"
  control_ips = "${module.do-hosts.control_ips}"
  domain = "mantl.io"
  edge_count = "${var.edge_count}"
  edge_ips = "${module.do-hosts.edge_ips}"
  short_name = "${var.short_name}"
  subdomain = ".do.test"
  worker_count = "${var.worker_count}"
  worker_ips = "${module.do-hosts.worker_ips}"
  kubeworker_count = "${var.kubeworker_count}"
  kubeworker_ips = "${module.do-hosts.kubeworker_ips}"
}

Configuration Variables¶

Configuration is done with a set of consistent variables across the providers:

control_count, worker_count, kubeworker_count, and edge_count: The count of nodes for each role.

control_ips, worker_ips, kubeworker_ips, and edge_ips

A comma-separated list of IPs. The cloud provider modules all export this as control_ips, worker_ips, kubeworker_ips, and edge_ips as well, so you can plug it in like so:

control_ips = "${module.your-hosts.control_ips}"

domain¶

The top level domain to add the records to.

Example: mantl.io

short_name¶: The same short name passed into the cloud provider, used to generate consistent names.

subdomain¶

A path to put between the top-level domain and the generated records. Must begin with a period.

Example: .apps

control_subdomain¶: The name for the control group (to generate control.yourdomain.com.) By default, this is control, but you can change it to whatever you’d like.

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