1.Overview of Count:
The count parameter on resources can simplify configurations and let you scale resources by simply incrementing a number.
Letβs assume, you need to create two EC2 instances. One of the common approaches is to define two separate resource blocks for aws_instance.
resource "aws_instance" "myfirstec2" {
# Changed AMI id based on the region
ami = "ami-0721c9af7b9b75114"
instance_type = "t2.micro"
}
resource "aws_instance" "mysecondec2" {
# Changed AMI id based on the region
ami = "ami-0721c9af7b9b75114"
instance_type = "t2.micro"
}
With the count parameter, we can simply specify the count value and the resource can be scaled accordingly.
resource "aws_instance" "myfirstec2" {
# Changed AMI id based on the region
ami = "ami-0721c9af7b9b75114"
instance_type = "t2.micro"
count = 2
}
2.Count Index : In resource blocks where the count is set, an additional count object is available in expressions, so you can modify the configuration of each instance.
This object has one attribute:
count.index β The distinct index number (starting with 0) corresponding to this instance.
Some of the challenges with Count Parameter:
With the below code, terraform will create 2 IAM users. But the problem is that all will have the same name.
resource "aws_iam_user" "iam_user"{
name = "financeuser"
count = 2
}
count.index allows us to fetch the index of each iteration in the loop.
resource "aws_iam_user" "iam_user" {
name = "financeuser.${count.index}"
count = 2
}
3.Conditional Expressions:
A conditional expression uses the value of a bool expression to select one of two values.
Syntax of Conditional expression:
condition ? true_val : false_val
If the condition is true then the result is true_val. If the condition is false then the result is false_val.
Letβs assume that there are two resource blocks as part of terraform configuration.
Depending on the variable value, one of the resource blocks will run.
If the variable is_test is true then dev environment
is_test is false then prod environment
#Conditional.tf
provider "aws" {
region = "us-west-2"
access_key = "YOUR-ACCESS-KEY"
secret_key = "YOUR-SECRET-KEY"
}
variable "istest" {}
resource "aws_instance" "dev" {
ami = "ami-082b5a644766e0e6f"
instance_type = "t2.micro"
count = var.istest == true ? 3 : 0
}
resource "aws_instance" "prod" {
ami = "ami-082b5a644766e0e6f"
instance_type = "t2.large"
count = var.istest == false ? 1 : 0
}
Terraform.tfvars
istest =true
#terraform.tfvars
istest =true
Conclusion:
Discussed about data types and variables, variable files in terraform.
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