This content originally appeared on DEV Community and was authored by Bhaskara teja Bulusu
Meta arguments
In terraform, the meta arguments are classified into 5 types
- depends_on
- count
- for_each
- provider
- lifecycle
count:
An argument used to create multiple resources with numeric indexing.
Usually, this is the length of the list.
- used for iterating over a list
example code:
// variables.tf
variable "bucket_count_list" {
type = list(string)
default = [ "bhaskaratejabulusu-bucket-day-08-list-1",
"bhaskaratejabulusu-bucket-day-08-list-2" ]
}
// main.tf
resource "aws_s3_bucket" "bucket1" {
count = length(var.bucket_count_list)
bucket = var.bucket_count_list[count.index] // iterates over a list
from 0 to [count-1]
}
for_each
An argument in terraform to create multiple resources with map/sets
- iterates over values / key-value pairs
- used in maps and sets
to use for_each the datatype must be either map or a set
example for set and map:
// variables.tf
// set
variable "bucket_count_set" {
type = set(string)
default = [ "bhaskaratejabulusu-bucket-day-08-set-1",
"bhaskaratejabulusu-bucket-day-08-set-2" ]
}
// map
variable "bucket_count_map" {
type = map(string)
default = {
"bucket1" = "bhaskaratejabulusu-bucket-day-08-map-1",
"bucket2" = "bhaskaratejabulusu-bucket-day-08-map-2"
}
}
// main.tf
// using set
resource "aws_s3_bucket" "bucket2" {
for_each = var.bucket_count_set
bucket = each.value // iterates over the set using a for loop
internally and retrieves every value
}
// using map
resource "aws_s3_bucket" "bucket3" {
for_each = var.bucket_count_map
bucket = each.value
}
depends_on
An argument used to explicitly specify that a resource or module must be created or updated after one or more other resources or modules. It establishes a manual dependency, ensuring the correct order of operations, even when there’s no direct reference between the resources.
example:
// main.tf
resource "aws_s3_bucket" "bucket1" {
count = length(var.bucket_count_list)
bucket = var.bucket_count_list[count.index]
}
resource "aws_s3_bucket" "bucket2" {
for_each = var.bucket_count_set
bucket = each.value
depends_on = [ aws_s3_bucket.bucket1 ]
}
In the above code, the bucket2 is dependent on bucket1 so terraform will wait for bucket1 to be created and then bucket2 will be created ensuring the correct order.
This content originally appeared on DEV Community and was authored by Bhaskara teja Bulusu