Terraform Meta-Arguments

What Are Meta-Arguments?
Meta-arguments are special arguments available to all Terraform resources. They modify how Terraform creates, destroys, or manages resources.

The key meta-arguments are:

• count
• for_each
• depends_on

COUNT
The count meta-argument lets you create multiple instances of the same resource using a simple integer.
Example:

resource "aws_s3_bucket" "example" {
count = 3
bucket = "my-bucket-${count.index}"
}

when to use:

• Creating N identical resources
• Feature flags (count = var.enabled ? 1 : 0)

Limitations:

• Index positions shift when items are removed leads to resource recreation risk.
• No stable index

FOR_EACH
for_each is more powerful and stable. It works with maps and sets, providing predictable resource identifiers.
Example:

resource "aws_s3_bucket" "example" {
for_each = toset(["bucket1", "bucket2", "bucket3"])
bucket = each.value
}

when to use:

• Creating resources using map or set data
• Complex configurations
• You want to update/add/remove resources without index shifting.

DEPENDS_ON
Sometimes Terraform can't detect relationships automatically. Use depends_on to control creation order.

Example:

resource "aws_s3_bucket" "dependent" {
bucket = "my-dependent-bucket"
depends_on = [aws_s3_bucket.primary]
}

when to use:

• Handling hidden dependencies
• Enforcing order in resource creation
• Working with modules

Use commands to test how meta arguments behave:

• terraform init
• terraform plan
• terraform apply
• terraform destroy

Video: https://youtu.be/XMMsnkovNX4?si=rncEENlnhlbe13BP