Terraform Apps and Infra 7 - Abstraction

In

Introduction

  • Terraform as a tool is cloud agnostic (it will support anything that exposes its API and has enough developer support to create a “provider” for it).
  • Terraform by itself will not natively abstract this at all, please consider if this is a good idea at all unless you have a really good use case.
    • If you did need to do this you would need to:
      • build a bunch of modules on top of things that abstracts the cloud layer from the module users.
      • allow them to specify the cloud provider as a variable (potentially controllable from some outside script).
  • You can check the registry.

Example: abstract when there is resource parity

Original DNS modules

Google Cloud DNS

  • modules/google/dns/record/main.tf

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    variable "count" = {}

    variable "domain_name_record" = {}
    variable "domain_name_zone" = {}
    variable "domain_name_target" = {}

    resource "google_dns_record_set" "frontend" {
      count = "${variable.count}"
      name  = "${var.domain_name_record}.${var.domain_name_zone}"
      type  = "CNAME"
      ttl   = 300

      managed_zone = "${var.domain_name_zone}"

      rrdatas = ["${var.domain_name_target}"]
    }

AWS

  • modules/aws/dns/record/main.tf

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    variable "count" = {}

    variable "domain_name_record" = {}
    variable "domain_name_zone" = {}
    variable "domain_name_target" = {}

    data "aws_route53_zone" "selected" {
      count = "${variable.count}"
      name  = "${var.domain_name_zone}"
    }

    resource "aws_route53_record" "www" {
      count   = "${variable.count}"
      zone_id = "${data.aws_route53_zone.selected.zone_id}"
      name    = "${var.domain_name_record}.${data.aws_route53_zone.selected.name}"
      type    = "CNAME"
      ttl     = "60"
      records = [${var.domain_name_target}]
    }

Generic inluding both module code

  • modules/generic/dns/record/main.tf

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    variable "cloud_provider" = { default = "aws" }

    variable "domain_name_record" = {}
    variable "domain_name_zone" = {}
    variable "domain_name_target" = {}

    module "aws_dns_record" {
      source             = "../../aws/dns/record"
      count              = "${var.cloud_provider == "aws" ? 1 : 0}"
      domain_name_record = "${var.domain_name_record}"
      domain_name_zone   = "${var.domain_name_zone}"
      domain_name_target = "${var.domain_name_target}"
    }

    module "google_dns_record" {
      source             = "../../google/dns/record"
      count              = "${var.cloud_provider == "google" ? 1 : 0}"
      domain_name_record = "${var.domain_name_record}"
      domain_name_zone   = "${var.domain_name_zone}"
      domain_name_target = "${var.domain_name_target}"
    }