Terraform: Deploy Multiple Resources

Last Updated on November 14, 2024 by Arnav Sharma

Using for_each in Terraform is a powerful way to deploy multiple resources based on a set of inputs. This method is particularly useful when you want to create multiple instances of a resource with only slight variations between them. Here’s how you can use for_each to deploy multiple resources:

Step 1: Define Your Input Set

First, you need to define a set of inputs that for_each will iterate over. This can be a list, set, or a map. Maps are often used because they allow you to easily associate each resource with a unique key.

For example, suppose you want to create multiple storage accounts in Azure. You might start with a map defining each account:

variable "storage_accounts" {
  description = "A map of storage accounts to create"
  type        = map(object({
    location = string
    account_tier = string
    account_replication_type = string
  }))

  default = {
    "account1" = {
      location = "eastus"
      account_tier = "Standard"
      account_replication_type = "LRS"
    },
    "account2" = {
      location = "westus"
      account_tier = "Standard"
      account_replication_type = "GRS"
    }
    # Add more accounts as needed
  }
}

Step 2: Use for_each in Your Resource Configuration

Next, use for_each in your resource block to iterate over each element in your input set. For each element, Terraform will create a new instance of the resource.

resource "azurerm_storage_account" "example" {
  for_each = var.storage_accounts

  name                     = each.key
  location                 = each.value.location
  account_tier             = each.value.account_tier
  account_replication_type = each.value.account_replication_type

  # Other required fields...
}

In this example, each.key is the key from the storage_accounts map (e.g., “account1”, “account2”), and each.value is the corresponding value, which is an object with properties like location, account_tier, and account_replication_type.

Step 3: Initialize and Apply Your Terraform Configuration

• Run terraform init to initialize the working directory.
• Run terraform plan to see what resources Terraform will create or modify.
• Run terraform apply to create the resources.

Additional Tips

• Dynamic Blocks: For more complex scenarios, you might use dynamic blocks within resources to create nested structures based on a list or map.
• Dependency Management: Be mindful of dependencies between resources. Terraform automatically handles dependencies, but in some cases, you may need to explicitly define them.
• State Management: Each resource created with for_each will have a unique identifier in the Terraform state file based on its key in the map. This helps in managing each resource independently.
• Modifying the Set: If you modify the input set (e.g., add or remove an item), Terraform will add, update, or destroy resources to match the new set.

Using for_each can significantly simplify your Terraform configurations, especially when dealing with multiple similar resources. It ensures that your configurations are more dynamic and easier to maintain.

FAQ – Terraform for_each

Q: What are the benefits of using Terraform to manage infrastructure?

Using Terraform, especially with modules, provides several benefits such as ensuring consistency across all resources, allowing you to manage and execute your Terraform projects efficiently. It includes features like remote state and execution, which make it easier to manage infrastructure across multiple cloud providers like AWS and Azure.

Q: How can you create multiple resources in Terraform?

You can use Terraform to create multiple resources by using the for_each argument or count within a single resource block. This approach allows you to provision multiple similar resources efficiently, instead of writing the same Terraform code multiple times.

Q: What is the advantage of using modules in Terraform?

Using modules in Terraform allows you to create and manage multiple resources more easily by reusing and sharing configuration across projects. Modules help in ensuring consistency and reducing redundancy in your Terraform project, making it easier to manage infrastructure at scale.

Q: How does Terraform manage multiple resources of the same type?

Terraform manages multiple resources of the same type using input variables and resource blocks. You can provision multiple resources by using a loop (for_each or count), which makes it easier to manage and scale infrastructure, whether in AWS or Azure.

Q: How does Terraform support managing infrastructure across multiple projects?

Terraform provides a platform that you can use to manage and execute your Terraform projects, whether using the community edition or HCP Terraform. This allows you to manage infrastructure across multiple projects consistently, using a tutorial-specific HCP Terraform organization or similar setups.

Q: How do modules in Terraform help in managing infrastructure?

Modules in Terraform help in managing infrastructure by allowing you to reuse configuration, ensuring consistency, and simplifying the management of resources across different environments. This modular approach is beneficial for handling large-scale infrastructure with multiple resources and projects.

Q: What is the difference between a security group and a resource group in AWS and Azure?

In AWS, a security group is used to control inbound and outbound traffic to your EC2 instances, whereas a resource group is a collection of AWS resources that share one or more tags or are in the same AWS CloudFormation stack. In Azure, a resource group is a container that holds related resources for an Azure solution, allowing you to manage and organize them as a unit. You can manage multiple Azure resources using a resource group.

Q: How can you manage multiple Azure resources efficiently using Terraform?

To manage multiple Azure resources efficiently, you can use the terraform tool provided by HashiCorp. Terraform allows you to define infrastructure as code and manage several resources in a resource group. You can create terraform modules for common configurations, making it easier to deploy and manage a set of strings or number of similar resources with different names across multiple Azure environments.

Q: What is a common approach to using Terraform with multiple EC2 instances in AWS?

A common approach is to use the same configuration of resources across multiple EC2 instances by defining a security group and an instance resource block with the use count feature. This allows you to easily scale your infrastructure by deploying several resources using a terraform module from the terraform registry.