Terraform: Conditional Deploy

Description:

So far, HCL has been an easy language to learn as you mostly just look at pointers and see what certain values are. I would say the hardest time I have had since starting is learning the count and for_each to deploying multiple reosurces and how to use them. In this post I will show how count is commonly not only used to deploy a group of resources, but conditionally deploy a resource based on any expression.

Note: You can see the code for this post on my Github repo.

To Resolve

1. First, take a look at main and notice the count. See how if var.region is southcentralus the count will equal 1 and if false, it will equal 0? That means that if I pass that value to that var it will deploy the resource and if I pass any other value it won’t.

   • If I were to run this as is it will create the Resource Group because region is set to southcentralus by default in variables.tf. You have to pass in a different value if you don’t want it be that value, that is how the default block works with variables.

2. In an example where the condition will equal 0 and NOT deploy the resource, we simply pass any other value to variable region and let the condition fail the check (since it will only deploy is region is southcentralus which is the default:

   • For example, if I set region to eastus at line 50 here and run an apply, it will delete the Resource Group previously deployed because the count would now be 0 instead of 1.
   • Also take note that both module azure_learning_rg and resource azurerm_management_lock both have to make that same reference. This is because you can’t tie a lock to a resource that doesn’t exist silly :)

3. See here for many examples of conditional deploys.

4. This is a common and core concept of Terraform so practice this alot because it is something you will be wanting to do often. I will try to come up with more posts with examples of this and link back to this one in the future.

5. Also, this can also be done with for_each with dynamic blocks as mentioned in this post on a different blog.