Terraform is a popular Infrastructure as Code (IAC) tool that allows you to manage and provision your infrastructure resources. When creating Terraform modules, you may find that you need to use a variable with different values in different environments. For example, you may have a development environment and a production environment, and you want to use different values for the same variable in each environment.
Here's how to use a variable with different values in different environments in Terraform:
Create a separate Terraform workspace for each environment: Terraform workspaces allow you to maintain separate state files for each environment. To create a workspace, use the terraform workspace new command and specify the name of the workspace. For example, to create a workspace for your development environment, use the following command:
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terraform workspace new dev
Define the variable with different values in each workspace: Next, define the variable with different values in each workspace. This can be done by using the terraform.workspace interpolation function. For example, to define the value of a variable named environment in the development workspace, you would use the following code:
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variable "environment" {
default = "${terraform.workspace == "dev" ? "development" : "production"}"
}
This code sets the value of the environment variable to "development" when the Terraform workspace is "dev", and to "production" for all other workspaces.
Use the variable in your Terraform module: Once you have defined the variable with different values in each workspace, you can use it in your Terraform module. For example, you could use the environment variable to conditionally set the value of another variable, such as a database connection string:
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variable "db_connection_string" {
default = "${var.environment == "development" ? "dev_db" : "prod_db"}"
}
This code sets the value of the db_connection_string variable to "dev_db" when the environment variable is set to "development", and to "prod_db" when it is set to "production".
Apply the Terraform changes: Finally, use the terraform apply command to apply the changes to your Terraform module. Be sure to switch to the correct workspace before applying the changes, so that the correct values for the variables are used.
In conclusion, using a variable with different values in different environments in Terraform is possible by creating separate Terraform workspaces, defining the variable with different values in each workspace, and using the Terraform.workspace interpolation function. By using this approach, you can ensure that the correct values for the variables are used in each environment, and maintain separate state files for each environment.
It is important to note that using Terraform workspaces is not the only way to manage variables with different values in different environments. Another approach is to use environment-specific variable files.
With this approach, you would create a separate variable file for each environment, and specify the location of the variable file using the -var-file flag when running Terraform. For example, if you have a development environment and a production environment, you would create a dev.tfvars file and a prod.tfvars file, and specify the location of the appropriate file when running Terraform:
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terraform apply -var-file=dev.tfvars
or
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terraform apply -var-file=prod.tfvars
In each environment-specific variable file, you would define the variables with the appropriate values for that environment. For example, in the dev.tfvars file, you could define the environment variable as follows:
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environment = "development"
And in the prod.tfvars file, you could define it as:
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environment = "production"
This approach has the advantage of keeping the environment-specific configuration separate from the main Terraform code, making it easier to manage and maintain. However, it does require you to manage separate variable files for each environment, which can add complexity to your workflow.