Define Common Tags as a map(string) Variable

Common Tags Map Variable

Consistent resource tagging is critical for cost allocation, compliance, and operations. A map(string) variable for common tags ensures every resource gets the same baseline tags.

Variable Definition

variable "tags" {
  type        = map(string)
  description = "Common tags applied to all resources"
  default = {
    Environment = "dev"
    ManagedBy   = "terraform"
  }
}

Extended Tags Pattern

variable "tags" {
  type        = map(string)
  description = "Common tags applied to all resources"
  default = {
    Environment = "dev"
    ManagedBy   = "terraform"
    Project     = "my-project"
    Team        = "platform"
    CostCenter  = "engineering"
  }
}

Merging with Resource-Specific Tags

resource "aws_instance" "web" {
  ami           = var.ami_id
  instance_type = var.instance_type

  tags = merge(var.tags, {
    Name = "web-server"
    Role = "frontend"
  })
}

The merge() function combines the common tags with resource-specific tags, where resource-specific values override common ones if keys collide.

Why map(string)?

• Flexible: Any number of key-value pairs without changing the type definition
• Mergeable: Works naturally with Terraform's merge() function
• AWS compatible: Maps directly to AWS resource tags
• Simple: No nested structures needed for flat tag maps

Organization Tagging Standards

Many organizations require specific tags for compliance:

Tag	Purpose	Example
Environment	Cost separation	dev, staging, prod
ManagedBy	Track IaC vs manual	terraform
Project	Cost allocation	my-project
Team	Ownership	platform-engineering
CostCenter	Finance tracking	CC-1234
DataClassification	Compliance	internal, confidential