Collection functions (length, flatten, merge) in Terraform - Mini Project: Build & Apply

Using Collection Functions in Terraform

📖 Scenario: You are managing infrastructure configurations using Terraform. You need to organize and analyze lists and maps of server names and their attributes.

🎯 Goal: Build a Terraform configuration that uses collection functions length, flatten, and merge to work with lists and maps.

📋 What You'll Learn

Create a variable with a nested list of server names

Create a variable with two maps of server attributes

Use length to find the number of servers in the flattened list

Use flatten to convert the nested list into a single list

Use merge to combine the two maps into one

💡 Why This Matters

🌍 Real World

Managing infrastructure often requires organizing lists of servers and their properties. Terraform collection functions help simplify this management.

💼 Career

Understanding how to manipulate collections in Terraform is essential for infrastructure as code roles, enabling efficient and scalable configuration management.

1

Create a nested list of server names

Create a variable called server_names with the nested list value [["web1", "web2"], ["db1", "db2"]].

Terraform

# Create a variable called server_names with the nested list [["web1", "web2"], ["db1", "db2"]]
# Your code here

Need a hint?

Use variable "server_names" { default = ... } to define the nested list.

2

Create two maps of server attributes

Create two variables called server_attrs1 and server_attrs2 with these exact maps: { web1 = "active", db1 = "active" } and { web2 = "inactive", db2 = "active" } respectively.

Terraform

variable "server_names" {
  default = [["web1", "web2"], ["db1", "db2"]]
}
# Create variables server_attrs1 and server_attrs2 with the specified maps
# Your code here

Need a hint?

Define each variable with variable "name" { default = { ... } } syntax.

3

Use length and flatten functions

Create a local variable called flat_servers that uses flatten(var.server_names). Then create another local variable called server_count that uses length(local.flat_servers).

Terraform

variable "server_names" {
  default = [["web1", "web2"], ["db1", "db2"]]
}

variable "server_attrs1" {
  default = { web1 = "active", db1 = "active" }
}

variable "server_attrs2" {
  default = { web2 = "inactive", db2 = "active" }
}

# Create local.flat_servers using flatten(var.server_names)
# Create local.server_count using length(local.flat_servers)
# Your code here

Need a hint?

Use locals { flat_servers = flatten(var.server_names) } and then server_count = length(local.flat_servers).

4

Merge the two server attribute maps

Add a local variable called all_server_attrs that merges var.server_attrs1 and var.server_attrs2 using the merge function.

Terraform

variable "server_names" {
  default = [["web1", "web2"], ["db1", "db2"]]
}

variable "server_attrs1" {
  default = { web1 = "active", db1 = "active" }
}

variable "server_attrs2" {
  default = { web2 = "inactive", db2 = "active" }
}

locals {
  flat_servers = flatten(var.server_names)
  server_count = length(local.flat_servers)
  # Create local.all_server_attrs by merging var.server_attrs1 and var.server_attrs2
  # Your code here
}

Need a hint?

Use all_server_attrs = merge(var.server_attrs1, var.server_attrs2) inside the locals block.