Hi Experts,
I am looking into the self service feature of terraform. I have a big question here. I would appreciate if someone one could help me here.
Lets say for example, We have to provide a self service feature for developers to provision Windows and Linux VM with 2 roles respectively (app and db).
I can dynamically create the hostname prefix using the input provided. Like
WINAPP
WINDB
RHELAPP
RHELDB
The suffix of the hostname should be 01 ,02,03 and it will go on depending on number of VM’s created. Ideally VM’s hostname should be in order. like WINAPP01,WINAPP02,WINAPP03 etc. Through terraform , is there a way look into currently deployed servers and allocate hostname dynamically like WINAPP## (## represents 01,02,03)?
Hello there!
You can create multiple resources using count, and then use ${count.index} to name the instance based on the count.
Additionally, you can pad the naming with zeros using the format function.
For example:
provider aws {}
variable os {
type = string
description = "OS - Windows or RHEL"
default = "RHEL"
}
variable ami_id {
# This is to facilitate the example. You could also pull the latest
# machine image based on the os variable.
type = string
description = "AWS Machine Image ID to facilitate example."
}
variable instance_type {
type = string
description = "Instance size"
default = "t2.micro"
}
variable instance_role {
type = string
description = "Instance role -- e.g. app or db."
}
variable instance_qty {
type = number
description = "Number of instances required."
default = 1
}
resource aws_instance example-vm {
count = var.instance_qty
ami = var.ami_id
instance_type = var.instance_type
tags = {
Name = format("${var.os}${var.instance_role}%02d", count.index + 1)
}
}
Sample plan output based on instance_qty of 2 –
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.
------------------------------------------------------------------------
An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
+ create
Terraform will perform the following actions:
# aws_instance.example-vm[0] will be created
+ resource "aws_instance" "example-vm" {
+ ami = "ami-06ffade19910cbfc0"
+ arn = (known after apply)
+ associate_public_ip_address = (known after apply)
+ availability_zone = (known after apply)
+ cpu_core_count = (known after apply)
+ cpu_threads_per_core = (known after apply)
+ get_password_data = false
+ host_id = (known after apply)
+ id = (known after apply)
+ instance_state = (known after apply)
+ instance_type = "t2.micro"
+ ipv6_address_count = (known after apply)
+ ipv6_addresses = (known after apply)
+ key_name = (known after apply)
+ network_interface_id = (known after apply)
+ outpost_arn = (known after apply)
+ password_data = (known after apply)
+ placement_group = (known after apply)
+ primary_network_interface_id = (known after apply)
+ private_dns = (known after apply)
+ private_ip = (known after apply)
+ public_dns = (known after apply)
+ public_ip = (known after apply)
+ security_groups = (known after apply)
+ source_dest_check = true
+ subnet_id = (known after apply)
+ tags = {
+ "Name" = "rhelapp01"
}
+ tenancy = (known after apply)
+ volume_tags = (known after apply)
+ vpc_security_group_ids = (known after apply)
+ ebs_block_device {
+ delete_on_termination = (known after apply)
+ device_name = (known after apply)
+ encrypted = (known after apply)
+ iops = (known after apply)
+ kms_key_id = (known after apply)
+ snapshot_id = (known after apply)
+ volume_id = (known after apply)
+ volume_size = (known after apply)
+ volume_type = (known after apply)
}
+ ephemeral_block_device {
+ device_name = (known after apply)
+ no_device = (known after apply)
+ virtual_name = (known after apply)
}
+ metadata_options {
+ http_endpoint = (known after apply)
+ http_put_response_hop_limit = (known after apply)
+ http_tokens = (known after apply)
}
+ network_interface {
+ delete_on_termination = (known after apply)
+ device_index = (known after apply)
+ network_interface_id = (known after apply)
}
+ root_block_device {
+ delete_on_termination = (known after apply)
+ device_name = (known after apply)
+ encrypted = (known after apply)
+ iops = (known after apply)
+ kms_key_id = (known after apply)
+ volume_id = (known after apply)
+ volume_size = (known after apply)
+ volume_type = (known after apply)
}
}
# aws_instance.example-vm[1] will be created
+ resource "aws_instance" "example-vm" {
+ ami = "ami-06ffade19910cbfc0"
+ arn = (known after apply)
+ associate_public_ip_address = (known after apply)
+ availability_zone = (known after apply)
+ cpu_core_count = (known after apply)
+ cpu_threads_per_core = (known after apply)
+ get_password_data = false
+ host_id = (known after apply)
+ id = (known after apply)
+ instance_state = (known after apply)
+ instance_type = "t2.micro"
+ ipv6_address_count = (known after apply)
+ ipv6_addresses = (known after apply)
+ key_name = (known after apply)
+ network_interface_id = (known after apply)
+ outpost_arn = (known after apply)
+ password_data = (known after apply)
+ placement_group = (known after apply)
+ primary_network_interface_id = (known after apply)
+ private_dns = (known after apply)
+ private_ip = (known after apply)
+ public_dns = (known after apply)
+ public_ip = (known after apply)
+ security_groups = (known after apply)
+ source_dest_check = true
+ subnet_id = (known after apply)
+ tags = {
+ "Name" = "rhelapp02"
}
+ tenancy = (known after apply)
+ volume_tags = (known after apply)
+ vpc_security_group_ids = (known after apply)
+ ebs_block_device {
+ delete_on_termination = (known after apply)
+ device_name = (known after apply)
+ encrypted = (known after apply)
+ iops = (known after apply)
+ kms_key_id = (known after apply)
+ snapshot_id = (known after apply)
+ volume_id = (known after apply)
+ volume_size = (known after apply)
+ volume_type = (known after apply)
}
+ ephemeral_block_device {
+ device_name = (known after apply)
+ no_device = (known after apply)
+ virtual_name = (known after apply)
}
+ metadata_options {
+ http_endpoint = (known after apply)
+ http_put_response_hop_limit = (known after apply)
+ http_tokens = (known after apply)
}
+ network_interface {
+ delete_on_termination = (known after apply)
+ device_index = (known after apply)
+ network_interface_id = (known after apply)
}
+ root_block_device {
+ delete_on_termination = (known after apply)
+ device_name = (known after apply)
+ encrypted = (known after apply)
+ iops = (known after apply)
+ kms_key_id = (known after apply)
+ volume_id = (known after apply)
+ volume_size = (known after apply)
+ volume_type = (known after apply)
}
}
Plan: 2 to add, 0 to change, 0 to destroy.
I hope that answers your question.
Regards,
-y