I have a root level variable, whose value is set at run time via a tfvar file. The tfvar file used and the var value can vary. Now I want to use this variable inside a module, the terraform way to do this is to set it up as a module variable and pass the root var when creating the module.
Except, I have this module used in our infrastructure several hundred times. Is repeating this variable 100s of times the only way to do this? Can the module access root namespace to grab the variable value?
I'm half tempted to use an external data script in the module to fetch the value instead, except, I wont know which tfvars file will be in effect at runtime..
Unfortunately, the only Terraform supported way is to pass the value into the module as a variable. Terraform has made me a copy/paste expert.
The only other approach that comes to mind that Terraform supports is making creative use of the External Data Source.
Related
I've set up a terraform project with the following folder structure:
modules/environments/[$environment,all]/regions/[$region,all]
modules/resources/[$resource]
environments/[$environment]/[$region]
In modules/resources I have folders like api, load balancer, etc. In modules/environments/[$environment,all]/regions/[$region,all], I import the required modules from modules/resources/[$resource]. Given the environment is prod, in eu-west-1 for example, I import modules from modules/environments/[prod,all]/regions/[eu-west-1,all].
If I add a new variable, I have to update the variables.tf file in all the affected places, and in every main.tf, where I assign the variables to the modules. This is a lot of effort.
It would be a much easier scenario if I wouldn't have to assign the variables in the "module" {} level, but it would automatically get the variables from the .tfvars file that is being used when planning or applying, but it's not the case.
Is there any workoaround for this?
We are using the roles pattern in puppet with hiera, meaning we have these lines in hiera.yaml:
- name: "Roles data"
path: "roles/%{::server_role}.yaml"
We have a custom fact that produces the role name when facter runs, but we would like to move this into hiera. Instead of the server_role variable being produced by facter, we want to specify the server_role inside of hiera, and let that variable be referenced elsewhere in hiera. Something like this:
hiera.yaml:
- name: "Per-node data"
path: "nodes/%{trusted.certname}.yaml"
- name: "Roles data"
path: "roles/%{lookup(server_role)}.yaml"
nodes/hostname.yaml:
server_role: foo_bar
I have seen this question, which says to use hiera() or lookup() but when I try to use those, I get this error message:
Interpolation using method syntax is not allowed in this context
So how can I use a hiera variable that's defined elsewhere in hiera?
Edit:
The prototypical code examples for defining roles could use any fact that's known to facter, often giving examples that are based on hostname. When you can't embed server config into hostname, a common(ish) workaround is to write a file such as /etc/server_role, but it seems to defeat the purpose of config management, when you need to ssh into a machine and edit a file. As the other comments & answer here so far mentioned, you could use an ENC, but again, the goal here is not to have config stored outside of version control. In fact, we have foreman as an ENC and we make a practice to never use it that way because then upgrades and other maintenance become unsustainable.
We could write a class which will pick up data from hiera, write it to /etc/server_role, and on the next puppet run, facter will pick that up and send it back to hiera, so then we'll have the server_role fact available to use in hiera.yaml. As gross as this sounds, so far, it's the best known solution. Still looking for better answers to this question.
Thanks.
As #MattSchuchard explained in comments, you cannot interpolate Hiera data into your Hiera config, because the config has to be known before the data can be looked up.
If you need a per-role level in your data hierarchy then an alternative would be to assign roles to machines via an external node classifier. You don't need it to assign any classes, just the server_role top-scope variable and probably also environment.
On the other hand, maybe you don't need a per-role level of your general hierarchy in the first place. Lots of people do roles & profiles without per-role data, but even if you don't want to do altogether without then it may be that module-specific data inside the module providing your role classes could be made to suffice.
I'm writing a terraform module that will select a value from a map, based on a key passed to it.
Nothing unusual.
The values in that map are secret however, and do not change based on who is calling the module.
A simple way I thought to keep those secrets secret would be to define the variable as a map in variables.tf in the module, put the keys/values in terraform.tfvars in the module, .gitignore terraform.tfvars, and encrypt it to terraform.tfvars.gpg or something.
But that doesn't work, because I have no default for the variable in the module terraform is expecting the variable to be set by the caller.
I can define the variable in the caller without a value, add it to the call, and either specify manually --var-file or include a terraform.tfvars in the caller. But that means the user having to remember a magic --var-file invocation or the duplication of terraform.tfvars everywhere my new module is used.
Remembering magic strings and duplication are both not good options.
Is it possible for a module to use its own tfvars to fill in variables not passed to it?
There is no way to use an automatic .tfvars file with a non-root module. Child modules always get all of their values from the calling module block (with default values inserted where appropriate); .tfvars is only for assigning values to root module variables.
Another option with similar characteristics to what you're describing is to use a data file in either JSON or YAML format inside the module directory, and load it in using the file function and one of the decoding functions. For example:
locals {
# This file must be created before using this module by
# decrypting secrets.yaml.gpg in this directory.
secrets = yamldecode(file("${path.module}/secrets.yaml"))
}
If the caller neglects to decrypt into the .gitignored file before using the module then the file call will fail with a "file not found" error message.
I'm not totally sure I understand but taking a stab. Are you using AWS? A fun solution I've used in the past is SSM parameters.
data "aws_ssm_parameter" "foo" {
name = "foo"
}
...
value = data.aws_ssm_parameter.foo.value
...
The SSM param could be created outside of tf and looked up in your module (and policies granting access depending on caller via IAM, or whatever).
This question already has answers here:
What is the difference between variables.tf and terraform.tfvars?
(5 answers)
Closed 3 years ago.
I've been researching this but can't find the distinction. A variables.tf file can store variable defaults/values, like a terraform.tfvars file.
What's the difference between these two and the need for one over the other? My understanding is if you pass in the var file as an argument in terraform via the command line.
There is a thread about this already and the only benefit seems to be passing in the tfvars file as an argument, as you can "potentially" do assignment of variables in a variable.tf file.
Is this the correct thinking?
The distinction between these is of declaration vs. assignment.
variable blocks (which can actually appear in any .tf file, but are in variables.tf by convention) declare that a variable exists:
variable "example" {}
This tells Terraform that this module accepts an input variable called example. Stating this makes it valid to use var.example elsewhere in the module to access the value of the variable.
There are several different ways to assign a value to this input variable:
Include -var options on the terraform plan or terraform apply command line.
Include -var-file options to select one or more .tfvars files to set values for many variables at once.
Create a terraform.tfvars file, or files named .auto.tfvars, which are treated the same as -var-file arguments but are loaded automatically.
For a child module, include an expression to assign to the variable inside the calling module block.
A variable can optionally be declared with a default value, which makes it optional. Variable defaults are used for situations where there's a good default behavior that would work well for most uses of the module/configuration, while still allowing that behavior to be overridden in exceptional cases.
The various means for assigning variable values are for dealing with differences. What that means will depend on exactly how you are using Terraform, but for example if you are using the same configuration multiple times to deploy different "copies" of the same infrastructure (environments, etc) then you might choose to have a different .tfvars file for each of these copies.
Because terraform.tfvars and .auto.tfvars are automatically loaded without any additional options, they behave similarly to defaults, but the intent of these is different. When running Terraform in automation, some users have their automation generate a terraform.tfvars file or .auto.tfvars just before running Terraform in order to pass in values the automation knows, such as what environment the automation is running for, etc.
The difference between the automatically-loaded .tfvars files and variable defaults is more clear when dealing with child modules. .tfvars files (and -var, -var-file options) only apply to the root module variables, while variable defaults apply when that module is used as a child module too, meaning that variables with defaults can be omitted in module blocks.
A variables.tf file is used to define the variables type and optionally set a default value.
A terraform.tfvars file is used to set the actual values of the variables.
You could set default values for all your variables and not use tfvars files at all.
Actually the objective of splitting between the definitions and the values, is to allow the definition of a common infrastructure design, and then apply specific values per environment.
Using multiple tfvars files that you give as an argument allows you to set different values per environment : secrets, VM size, number of instances, etc.
I am attempting to learn puppet, and so far so good.
What I am having an issue with is using a variable that I have set for a node or group in the web console.
I created a variable called myCustomSetting, and then in a manifest:
file {/var/tmp/myfile.txt
ensure => file,
content => $::myCustomSetting,
}
When I apply the manifest with puppet apply mytest.pp, there are no errors, but the file is empty? What am I missing?
The double semi colon indicate that you wish to reach the top level scope, where you supposedly declared your variable. Check that your variable has not been declared in a local scope.