How to pass terraform outputs variables into ansible as vars_files? - ansible

Question

I am provisioning AWS infrastructure using terraform and want to pass variables such as aws_subnet_id and aws_security_id into ansible playbook using vars_file (don't know if there is any other way though). How can I do that?

Answer 1

I use Terraform local_file to create an Ansible vars_file. I add a tf_ prefix to the variable names to make it clear that they originate in Terraform:
# Export Terraform variable values to an Ansible var_file
resource "local_file" "tf_ansible_vars_file_new" {
content = <<-DOC
# Ansible vars_file containing variable values from Terraform.
# Generated by Terraform mgmt configuration.
tf_environment: ${var.environment}
tf_gitlab_backup_bucket_name: ${aws_s3_bucket.gitlab_backup.bucket}
DOC
filename = "./tf_ansible_vars_file.yml"
}
Run terraform apply to create Ansible var_file tf_ansible_vars_file.yml containing Terraform variable values:
# Ansible vars_file containing variable values from Terraform.
# Generated by Terraform mgmt configuration.
tf_environment: "mgmt"
tf_gitlab_backup_bucket_name: "project-mgmt-gitlab-backup"
Add tf_ansible_vars_file.yml to your Ansible playbook:
vars_files:
- ../terraform/mgmt/tf_ansible_vars_file.yml
Now, in Ansible the variables defined in this file will contain values from Terraform.
Obviously, this means that you must run Terraform before Ansible. But it won't be so obvious to all your Ansible users. Add assertions to your Ansible playbook to help the user figure out what to do if a tf_ variable is missing:
- name: Check mandatory variables imported from Terraform
assert:
that:
- tf_environment is defined
- tf_gitlab_backup_bucket_name is defined
fail_msg: "tf_* variable usually defined in '../terraform/mgmt/tf_ansible_vars_file.yml' is missing"
UPDATE: An earlier version of this answer used a Terraform template. Experience shows that the template file is error prone and adds unnecessarily complexity. So I moved the template file to the content of the local_file.

Answer 2

terraform outputs are an option, or you can just use something like:
provisioner "local-exec" {
command = "ANSIBLE_HOST_KEY_CHECKING=\"False\" ansible-playbook -u ${var.ssh_user} --private-key=\"~/.ssh/id_rsa\" --extra-vars='{"aws_subnet_id": ${aws_terraform_variable_here}, "aws_security_id": ${aws_terraform_variable_here} }' -i '${azurerm_public_ip.pnic.ip_address},' ansible/deploy-with-ansible.yml"
}
or you can do a sed thing ... as a local provisioner to update the var file..
or you can use terraform outputs.... your preference....

Answer 3

I highly recommend this script. It works well and is maintained by Cisco and will give you more flexibility.
https://github.com/CiscoCloud/terraform.py

Answer 4

Since I want to run both terraform plan and ansible --check in a pull request with a CI, I've decided to go with terraform output.
Basically this is how I run my Ansible now and it gets all outputs from terraform :
With the following output
// output.tf
output "tf_gh_deployment_status_token" {
value = var.GH_DEPLOYMENT_STATUS_TOKEN
sensitive = true
}
Running a bit modified terraform output parsed with jq :
$ terraform output --json | jq 'with_entries(.value |= .value)'
{
"tf_gh_deployment_status_token": "<some token>"
}
This makes it great to run with --extra-args with Ansible :
$ ansible-playbook \
-i ./inventory/production.yaml \
./playbook.yaml \
--extra-vars "$(terraform output --json | jq 'with_entries(.value |= .value)')"
Now I can use {{ tf_gh_deployment_status_token }} anywhere in my playbook.

Answer 5

Use terraform outputs - https://www.terraform.io/intro/getting-started/outputs.html (it is not clear if you are using it already)
Then using command like terraform output ip, you can then use those values in your scripts to generate or populate other files like inventory files or vars_file.
Another option is to use terraform templates and render your files like inventory files from terraform itself and then use it from Ansible.