I have resources defined in .tf files that are generic to several applications. I populate many of the fields via a .tfvars file. I need to omit some of the resources entirely based on variables in the .tfvars.
For example if I have a resource like:
resource "cloudflare_record" "record" {
zone_id = "${data.cloudflare_zones.domain.zones[0].id}"
name = "${var.subdomain}"
value = "${var.origin_server}"
type = "CNAME"
ttl = 1
proxied = true
}
But then I declare something like cloudflare = false in my .tfvars file I'd like to be able to do something like this:
if var.cloudflare {
resource "cloudflare_record" "record" {
zone_id = "${data.cloudflare_zones.domain.zones[0].id}"
name = "${var.subdomain}"
value = "${var.origin_server}"
type = "CNAME"
ttl = 1
proxied = true
}
}
I've looked at dynamic blocks but that looks like you can only use those to edit fields and blocks within a resource. I need to be able to ignore an entire resource.
Add a count parameter with a ternary conditional using the variable declared in .tfvars like this:
resource "cloudflare_record" "record" {
count = var.cloudflare ? 1 : 0
zone_id = "${data.cloudflare_zones.domain.zones[0].id}"
name = "${var.subdomain}"
value = "${var.origin_server}"
type = "CNAME"
ttl = 1
proxied = true
}
In this example var.cloudflare is a boolean declared in the .tfvars file. If it is true a count of 1 record will be created. If it is false a count of 0 record will be created.
After the count apply the resource becomes a group, so later in the reference use 0-index of the group:
cloudflare_record.record[0].some_field
Expanding on #Joel Guerra's answer, after you use count to determine whether to deploy the resource or not, you can use the one() function to refer to the resource without an index (i.e. without having to use [0]).
For example, after defining the resource like below
resource "cloudflare_record" "record" {
count = var.cloudflare ? 1 : 0
}
Define a local variable like below
locals {
cloudflare_record_somefield = one(cloudflare_record.record[*].some_field)
}
Now instead of cloudflare_record.record[0].some_field, you can use
local.cloudflare_record_somefield
If the count is 0 (e.g. var.cloudflare is false and the resource wasn't created) then local.cloudflare_record_somefield would return null (instead of returning an error when indexing using [0]).
Reference: https://developer.hashicorp.com/terraform/language/functions/one
An issue i'm seeing this with is if the resource your trying to create is already using a for_each then you can't use both count and for_each in the resource. I'm still trying to find an answer on this will update if I find something better.
Related
I see people using count to block resource creation in terraform. I want to create some resources if a condition is set to true. Is there such a thing same as in CloudFormation?
You answered yourself, the most similar thing is the count
You can use it combined with a conditional expression, like
resource "x" "y"{
count = var.tag == "to_deploy" ? 1 : 0
}
But this is just a stupid example, you can put everything, also use functions
count = max(var.array) >= 3 ? 1 : 0
And if you need to put a condition on something more complex, you can evaluate to use a locals block where do all elaboration you need, and just use some bool, or what you want, resultant from that in conditional expression.
I would like to help you more, but I should know your specific case, what are the conditions you would have.
In CloudFormation a "condition" is a top-level object type alongside resources, outputs, mappings, etc.
The Terraform language takes a slightly more general approach of just having values of various data types, combining and transforming them using expressions. Therefore there isn't a concept exactly equivalent to CloudFormation's "conditions", but you can achieve a similar effect in other ways using Terraform.
For example, if you want to encode the decision rule in only a single place and then refer to it many times then you can define a Local Value of boolean type and then refer to that from multiple resource blocks. A local value of boolean type is essentially equivalent to a condition object in CloudFormation. The CloudFormation documentation page you linked to has, at the time of writing, an example titled "Simple condition" and the following is a roughly-equivalent version of that example in the Terraform language:
variable "environment_type" {
type = string
validation {
condition = contains(["prod", "test"], var.environment_type)
error_message = "Must be either 'prod' or 'test'."
}
}
locals {
create_prod_resources = (var.environment_type == "prod")
}
resource "aws_instance" "example" {
ami = "ami-0ff8a91507f77f867"
instance_type = "..."
}
resource "aws_ebs_volume" "example" {
count = local.create_prod_resources ? 1 : 0
availability_zone = aws_instance.example.availability_zone
}
resource "aws_volume_attachment" "example" {
count = local.create_prod_resources ? 1 : 0
volume_id = aws_ebs_volume.example[count.index].id
instance_id = aws_instance.example.id
device = "/dev/sdh"
}
Two different resource blocks can both refer to local.create_prod_resources, in the same way that the two resources MountPoint and NewVolume can refer to the shared condition CreateProdResources in the CloudFormation example.
I would like to set the disk_size doing something like the following:
resource "google_compute_disk" "terraform-additional-persistent-disk" {
name = "terraform-additional-persistent-disk"
zone = local.zone
type = local.default_disk_type
size = exists(local.default_disk_size) ? local.default_disk_size : 50
image = local.default_ubuntu_image
labels = {
created_by = "terraform"
}
}
However, I have not been able to find a exists function in Terraform. The main aim is to take the value of a variable/local if it exists and, if it has not been declared anywhere, then take the value I pass as second argument.
I have been checking other questions like 1 but neither can nor try function are helping me achieve my goal. I will always get either A local value with the name "default_disk_size" has not been declared or An input variable with the name "default_disk_size" has not been declared (depending on whether I use a non-existing local or var).
I have even tried to run the following, but it will always raise an exception if the variable/local has not been set. Is there a way of achieving this without explicitly declaring the variable with a default value of null/""?
Thanks!
resource "google_compute_disk" "terraform-additional-persistent-disk" {
name = "terraform-additional-persistent-disk"
zone = local.zone
type = local.default_disk_type
size = merge({sizee=50}, {sizee = local.default_disk_sizee})["sizee"]
image = local.default_ubuntu_image
labels = {
created_by = "terraform"
}
}
I think you're coming at this with the idea that input variables and locals may or may not exist at the time this resource is created, like they are system environment variables or something. However in Terraform, those things have to be explicitly declared in one of the .tf files in the same folder as the file your google_compute_disk.terraform-additional-persistent-disk is declared.
There would be no way in Terraform's syntax to have either local or input variables appear dynamically at runtime, they have to be declared ahead of time in your code. They will always exist.
If you want to allow someone using your Terraform code the option of passing in a variable or not, you have to explicitly declare the variable, and give it a default value. Then the person using your Terraform code can optionally override that default value. Like this:
variable "disk_size" {
type = number
default = 50
description = "The size of the additional persistent disk"
}
resource "google_compute_disk" "terraform-additional-persistent-disk" {
name = "terraform-additional-persistent-disk"
zone = local.zone
type = local.default_disk_type
size = var.disk_size
image = local.default_ubuntu_image
labels = {
created_by = "terraform"
}
}
Then when someone uses your Terraform code, if they don't specify a value for the disk_size input variable, the default of 50 will be used, but if they do specify something, then the value they specified will be used.
we have a standard naming convention within azure, but in order to sometimes be able to make an exception, it must be possible to provide a name yourself when calling the module
How can be indicated within count which variable Var.Log Name or Local.ComponetName should be used and how can we pass this to the name of the resource
resource "azurerm_log_analytics_workspace" "LOG" {
count = length(var.LOG_Name) == "" ? length(local.ComponentNames) : null
name = var.LOG_Name[count.index] == "" ? local.ComponentNames[count.index] : null
resource_group_name = element(var.resourcegroup_name[*], count.index)
location = var.location
sku = var.LOG_Sku
retention_in_days = var.LOG_RetentionPeriod
}
What you are actually looking for are loops. Within loops you can reference the name of the resource and in case there is no such resource available it won't create them, which seems to be what you tried to indicate when mentioning null.
Here is a great link regarding loops in terraform that thoroughly explains the different types of loops and how to use them: https://blog.gruntwork.io/terraform-tips-tricks-loops-if-statements-and-gotchas-f739bbae55f9
I have a question about passing multiple values to a variable in Terraform. I can't find the answer anywhere and I am not sure if this is even possible. In our environment when we create AWS resources such VPC and add a tag name to it like project-environment-VPC e.g. cvs-production-VPC. How would I do the same when I am trying to create the resource using Terraform? I tried the below approach and it didn't work:
resource "aws_vpc" "main" {
cidr_block = var.aws_cidr
instance_tenancy = "default"
enable_dns_support = true
enable_dns_hostnames = true
tags = {
Name = ${var.project}-${var.environment}-${"VPC"}
}
}
If it is not possible - perhaps there is a workaround? Thanks in advance for any replies.
The current Name tag value causes Invalid Character error using Terraform 0.14.6.
Change the Name tag value as below to resolve the issue.
Name = "${var.project}-${var.environment}-${"VPC"}"
I have a list variable "test" in variables.tf. I am trying to use this list variable inside my zone.tf .
I do not want to use list indexes here infact I want to run a loop to get all the values of the list from list variable dynamically. How can I accomplish this ? Any help is much appreciated.
I have tried to use count in test.tf inside resource resource "aws_route53_record" but it creates multiple record sets which I do not want as I just need a single record set with multiple records
resource "aws_route53_record" "test" {
zone_id = "${data.aws_route53_zone.dns.zone_id}"
name = "${lower(var.environment)}xyz"
type = "CAA"
ttl = 300
count = "${length(var.test)}"
records = [
"0 issue \"${element(var.test, count.index)}\"",
]
}
variables.tf :-
variable "test" {
type = "list"
default = ["godaddy.com", "Namecheap.org"]
}
zone.tf :-
resource "aws_route53_record" "test" {
zone_id = "${data.aws_route53_zone.dns.zone_id}"
name = "${lower(var.environment)}xyz"
type = "CAA"
ttl = 300
records = [
"0 issue \"${var.test[0]}\"",
"0 issue \"${var.test[1]}\"",
]
}
Expecting to get the one record set with two records.
Actual :- getting Two record sets with two records.
so if I am understanding correctly you want to associate two records with your zone, but right now when using count you are getting two zones with one record.
This is because by specifying county terraform will create the resource that has the count attribute on it equal to the number of count.
The issue is fundamentally that right now you have a list variable and are trying to pass it to where a list is expected by extracting each individual element of the list to put back element by element into the list attribute.
Rather than go through that additional work an easier solution would be to just add the additional parts of the string, the "0 issue" part to the definition of the variable and then just pass the whole list object in as shown below
variable "test" {
type = "list"
default = ["0 issue godaddy.com", "0 issue Namecheap.org"]
}
zone.tf :-
resource "aws_route53_record" "test" {
zone_id = "${data.aws_route53_zone.dns.zone_id}"
name = "${lower(var.environment)}xyz"
type = "CAA"
ttl = 300
records = ["${var.test}"]
}
This will then pass the list in for that attribute and terraform will take care of the marshaling and unmarshaling and handling of the list. I hope this answers your question.