Provisioning multiple Terraform resources with the count property

Terraform's count meta-argument allows you to efficiently create multiple instances of the same resource block with varying configurations. This eliminates the need to define repetitive blocks for each resource instance.

Using the count Meta-Argument

The count meta-argument is applied within a resource block. Here's the syntax:

resource "<resource_type>" "<resource_name>" {
  count = <number_of_instances>

  # ... other resource configuration options

  dynamic "<dynamic_block_name>" {
    # ... configuration for dynamic attributes (optional)
  }
}

• <resource_type>: The type of resource you're configuring (e.g., aws_instance, null_resource).
• <resource_name>: A unique name for the resource.
• <number_of_instances>: The number of resource instances to create.
• dynamic "<dynamic_block_name>" (Optional): This block allows you to configure attributes dynamically based on the count (explained later).

Example - Creating Web Servers

Let's create three web server instances with unique names and IP addresses:

resource "aws_instance" "web_server" {
  count = 3

  ami           = "ami-01234567"
  instance_type = "t2.micro"

  tags = {
    Name = format("web-server-%d", count.index + 1)
  }

  dynamic "assign_ip" {
    for_each = toset([10, 20, 30])
    content {
      name = "PublicIp"
      value = assign_ip.key
    }
  }
}

Explanation:

• count = 3: This creates three instances of the aws_instance resource.
• tags.Name: The format function dynamically generates unique names using a counter (count.index + 1).
• dynamic "assign_ip": This block assigns a unique public IP address from the toset list to each instance. The assign_ip.key references the current element in the loop.

Benefits of Using count

• Reduced Code Duplication: Avoids writing the same resource configuration for each instance.
• Improved Readability: Makes your configuration concise and easier to understand.
• Scalability: Easily adjust the number of instances by changing the count value.

Advanced Usage with dynamic

The dynamic block within count allows you to configure attributes based on the current instance iteration. This is useful for assigning unique values or performing conditional logic based on the instance number.

By leveraging the count meta-argument effectively, you can streamline your Terraform configurations and efficiently manage multiple instances of the same resource with dynamic variations.