Terraform – first experience

Having access to an Azure credit through my workplace, I’ve begun training and testing various things within Azure, and recently I was looking at ARM templates for VM deployment. This research led me to stumble across Terraform as an infrastructure-as-code deployment tool.

I started messing around with Terraform to deploy a basic set of Azure resources using these two guides:

Using Peter’s example was great, although I had to make a few tweaks since the module syntax has changed. In the near future I’ll post a full example of what I used recently for my first template. Terraform documentation has been excellent as I’ve worked through syntax and various examples, which is a great surprise.

I’ve found that I appreciate building a template in Terraform much more than an ARM template. Part of this is the easier syntax and readability, and the logical manner that I’ve seen others use Terraform .tf files for segregating resource deployment.

I think that the other primary factor is because declarative Terraform is what I’ve seen referred to as “idempotent” – a new word for me I’ve only ever seen used in this context. The answer on this StackOverflow question gives a great description of this context, and its clearly descriptive of how Terraform operates.

If I build an ARM template and apply it, it will deploy the resource as I’ve described it. And then if I apply that template again, it will attempt to build another of that resource. And if I modify the template and apply it again, it will attempt to create that slightly modified resource, leaving me with 3 different resources.

Terraform instead gives the ability to declare “what I want it to look like”, and ensures that the actual state matches the declared state. There are genuinely good reasons to use both approaches but right now this idempotent-style of deployment is new and attractive to me.

Soon on the horizon in my sandbox is to utilize remote state in an Azure blob storage to facilitate team work within one environment.

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