terraform-inventory/README.md

Terraform Inventory

This is a little Go app which generates a dynamic Ansible inventory from a Terraform state file. It allows one to spawn a bunch of instances with Terraform, then (re-)provision them with Ansible.

The following providers are supported:

• AWS
• DigitalOcean
• CloudStack
• VMware
• OpenStack
• Google Compute Engine
• SoftLayer
• Exoscale

It's very simple to add support for new providers. See pull requests with the provider label for examples.

Help Wanted 🙋

This library is stable, but I've been neglecting it somewhat on account of no longer using Ansible at work. Please drop me a line if you'd be interested in helping to maintain this tool.

Installation

On OSX, install it with Homebrew:

brew install terraform-inventory

Alternatively, you can download a release suitable for your platform and unzip it. Make sure the terraform-inventory binary is executable, and you're ready to go.

Usage

If you are using remote state (or if your state file happens to be named terraform.tfstate), cd to it and run:

ansible-playbook --inventory-file=/path/to/terraform-inventory deploy/playbook.yml

This will provide the resource names and IP addresses of any instances found in the state file to Ansible, which can then be used as hosts patterns in your playbooks. For example, given for the following Terraform config:

resource "digitalocean_droplet" "my_web_server" {
  image = "centos-7-0-x64"
  name = "web-1"
  region = "nyc1"
  size = "512mb"
}

The corresponding playbook might look like:

- hosts: my_web_server
  tasks:
    - yum: name=cowsay
    - command: cowsay hello, world!

Note that the instance was identified by its resource name from the Terraform config, not its instance name from the provider. On AWS, resources are also grouped by their tags. For example:

resource "aws_instance" "my_web_server" {
  instance_type = "t2.micro"
  ami = "ami-96a818fe"
  tags = {
    Role = "web"
    Env = "dev"
  }
}

resource "aws_instance" "my_worker" {
  instance_type = "t2.micro"
  ami = "ami-96a818fe"
  tags = {
    Role = "worker"
    Env = "dev"
  }
}

Can be provisioned separately with:

- hosts: role_web
  tasks:
    - command: cowsay this is a web server!

- hosts: role_worker
  tasks:
    - command: cowsay this is a worker server!

- hosts: env_dev
  tasks:
    - command: cowsay this runs on all dev servers!

More Usage

Ansible doesn't seem to support calling a dynamic inventory script with params, so if you need to specify the location of your state file or terraform directory, set the TF_STATE environment variable before running ansible-playbook, like:

TF_STATE=deploy/terraform.tfstate ansible-playbook --inventory-file=/path/to/terraform-inventory deploy/playbook.yml

or

TF_STATE=../terraform ansible-playbook --inventory-file=/path/to/terraform-inventory deploy/playbook.yml

If TF_STATE is a file, it parses the file as json, if TF_STATE is a directory, it runs terraform state pull inside the directory, which is supports both local and remote terraform state.

It looks for state config in this order

• TF_STATE: environment variable of where to find either a statefile or a terraform project
• TI_TFSTATE: another environment variable similar to TF_STATE
• terraform.tfstate: it looks in the state file in the current directory.
• .: lastly it assumes you are at the root of a terraform project.

Alternately, if you need to do something fancier (like downloading your state file from S3 before running), you might wrap this tool with a shell script, and call that instead. Something like:

#!/bin/bash
/path/to/terraform-inventory $@ deploy/terraform.tfstate

Then run Ansible with the script as an inventory:

ansible-playbook --inventory-file=bin/inventory deploy/playbook.yml

This tool returns the public IP of the host by default. If you require the private IP of the instance to run Ansible, set the TF_KEY_NAME environment variable to private_ip before running the playbook, like:

TF_KEY_NAME=private_ip ansible-playbook --inventory-file=/path/to/terraform-inventory deploy/playbook.yml

Development

It's just a Go app, so the usual:

go get github.com/adammck/terraform-inventory

To test against an example statefile, run:

terraform-inventory --list fixtures/example.tfstate
terraform-inventory --host=52.7.58.202 fixtures/example.tfstate

To update the fixtures, populate fixtures/secrets.tfvars with your DO and AWS account details, and run fixtures/update. To run a tiny Ansible playbook on the example resourecs, run:

TF_STATE=fixtures/example.tfstate ansible-playbook --inventory-file=/path/to/terraform-inventory fixtures/playbook.yml

You almost certainly don't need to do any of this. Use the tests instead.

Acknowledgements

Development of #14, #16, and #22 was generously sponsored by Transloadit.

License

MIT.