How I setup sandboxes

Context: I work in projects for customers. Mostly involving Ansible, Terraform, GitLab, Vault and Terraform Enterprise.

So here is a method I use to manage my work. It helped me over and over again in the last few years. This method does cost some time at the beginning of a project, but has saved me many hours later in the project.

At the start of a project I’ll keep my eyes and ears open to understand the environment I will be working in. These details include:

I’ll mostly know what the deliverable is up-front. Sometimes it’s difficult to visualize what is expected anyway, that’s just something I’m not very good at. A deliverable can be something like:

  1. Upgrade the application.
  2. Scale up the application.
  3. Do a performance tests.
  4. Make a health-check report.

Note, that’s just an example, but it’s something along those lines.

Anyway, once I know what to do and know where to do it, I’ll start drawing. Images like this, quite abstract:

Rough Architecture

This imaging gives me a clue how to start coding. Coding I’ll mostly use Terraform to deploy infrastructure. It nearly always ends up with some instances, a load-balancer and everything required to support the application.

When using instances, It’s quite annoying that the IP/hostname keeps changing every deployment. So I’ll let Terraform write an ssh-configuration file.

First; I’ll include a conf.d directory from ~/.ssh/config:

Include conf.d/*

(And just to be explicit, this is done manually, once, not by Terraform.)

Next I’ll let Terraform write an ssh configuration using a template (templates/ssh_config.tpl):

%{ for index, instance in instances ~}
Host instance-${ index }
  HostName ${ instance }
  User ec2-user
  IdentityFile ${ ssh_key_path }

%{ endfor }

In the above example; a loop is created using instances. The index is used to count in what loop we’re in.

Next, I’ll let Terraform place the ~/.ssh/conf.d/SOME_PROJECT.conf file:

# Place the SSH configuration.
resource "local_file" "ssh_config" {
  content = templatefile("${path.module}/templates/ssh_config.tpl", {
    ssh_key_path = local_sensitive_file.default.filename
    instances    = aws_instance.default[*].public_ip
  filename = pathexpand("~/.ssh/config")

You see that both ssh_key_path and instances are sent to the template. And what’s missing here is all the code to make the instances and sensitive files. You’ll find many other articles describing that process.

Now if you terraform apply, Terraform will create instances and drop a .ssh config file, so you can simply type ssh instance-0. Also good for Ansible, because Ansible uses the .ssh configuration as well. So the inventory can simply contain the hostname instance-0. (And Terraform can create that inventory as well!)

What really helps here too, is to write modules/roles/libraries that can be re-used. This is an extremely time-consuming process, not always possible in a budget, but is a quick win for future projects. Such a next project would simply be an Ansible playbook for example that lists a couple of Ansible roles and variables. In some cases it’s difficult to justify the time-investment, but I always try.

Now comes the ethical part; What do customers actually pay for? My time? A deliverable? The truth is probaly somewhere in the middle. I work for Adfinis, so using the above pattern has a couple of advantages for both me/us and the customer or project:

  1. We’re reusing code that’s in use elsewhere. It probalby works, I don’t need to worry too much about the technicalities.
  2. It much quicker to build a production-like sandbox.
  3. It’s easier to collaborate; a colleague can also spin up a sandbox.

Anyway, hope this is useful to you, hope you get the benefits of this method, just as I do!