resource-tagging

# Resource Tagging

Apply comprehensive cloud resource tagging strategies to enable cost allocation, ownership tracking, compliance enforcement, and infrastructure automation across multi-cloud environments.

## Purpose

Resource tagging provides the foundational metadata layer for cloud governance. Tags enable precise cost allocation (reducing unallocated spend by up to 80%), rapid ownership identification, compliance scope definition, and automated lifecycle management. Without proper tagging, cloud costs become untrackable, security incidents lack context, and automation policies fail to target resources effectively.

## When to Use

Use resource tagging when:

- Implementing cloud governance frameworks for cost allocation and accountability
- Building FinOps practices requiring spend visibility by team, project, or department
- Enforcing compliance requirements (PCI, HIPAA, SOC2) through automated policies
- Setting up automated resource lifecycle management (backup, monitoring, shutdown)
- Managing multi-tenant or multi-project cloud environments
- Implementing disaster recovery and backup policies based on criticality
- Tracking resource ownership for security incident response
- Optimizing cloud costs through spend analysis and showback/chargeback

## Minimum Viable Tagging Strategy

Start with the **"Big Six"** required tags for all cloud resources:

| Tag | Purpose | Example Value |
|-----|---------|---------------|
| **Name** | Human-readable identifier | `prod-api-server-01` |
| **Environment** | Lifecycle stage | `prod` \| `staging` \| `dev` |
| **Owner** | Responsible team contact | `platform-team@company.com` |
| **CostCenter** | Finance code for billing | `CC-1234` |
| **Project** | Business initiative | `ecommerce-platform` |
| **ManagedBy** | Resource creation method | `terraform` \| `pulumi` \| `manual` |

**Optional tags** to add based on specific needs:

- **Application**: Multi-app projects requiring app-level isolation
- **Component**: Resource role (`web`, `api`, `database`, `cache`)
- **Backup**: Backup policy (`daily`, `weekly`, `none`)
- **Compliance**: Regulatory scope (`PCI`, `HIPAA`, `SOC2`)
- **SLA**: Service level (`critical`, `high`, `medium`, `low`)

## Tag Naming Conventions

Choose ONE naming convention organization-wide and enforce consistently:

| Convention | Format | Example | Best For |
|------------|--------|---------|----------|
| **PascalCase** | `CostCenter`, `ProjectName` | AWS standard | AWS-first orgs |
| **lowercase** | `costcenter`, `project` | GCP labels (required) | GCP-first orgs |
| **kebab-case** | `cost-center`, `project-name` | Azure (case-insensitive) | Azure-first orgs |
| **Namespaced** | `company:environment`, `team:owner` | Multi-org tag policies | Large enterprises |

**Critical:** Case sensitivity varies by provider:
- **AWS**: Case-sensitive (`Environment` ≠ `environment`)
- **Azure**: Case-insensitive (`Environment` = `environment`)
- **GCP**: Lowercase required (`environment` only)
- **Kubernetes**: Case-sensitive (`environment` ≠ `Environment`)

## Tag Categories

For detailed taxonomy of all tag categories, see `references/tag-taxonomy.md`.

### Technical Tags
Operations-focused metadata: Name, Environment, Version, ManagedBy

### Business Tags
Cost allocation metadata: Owner, CostCenter, Project, Department

### Security Tags
Compliance metadata: Confidentiality, Compliance, DataClassification, SecurityZone

### Automation Tags
Lifecycle metadata: Backup, Monitoring, Schedule, AutoShutdown

### Operational Tags
Support metadata: SLA, ChangeManagement, CreatedBy, CreatedDate

### Custom Tags
Organization-specific metadata: Customer, Application, Component, Stack

## Cloud Provider Tag Limits

| Provider | Tag Limit | Key Length | Value Length | Case Sensitive | Inheritance |
|----------|-----------|------------|--------------|----------------|-------------|
| **AWS** | 50 user-defined | 128 chars | 256 chars | Yes | Via tag policies |
| **Azure** | 50 pairs | 512 chars | 256 chars | No | Via Azure Policy |
| **GCP** | 64 labels | 63 chars | 63 chars | No | Via org policies |
| **Kubernetes** | Unlimited | 253 prefix + 63 name | 63 chars | Yes | Via namespace |

## Tag Enforcement Patterns

### Infrastructure as Code (Recommended)

Apply tags automatically via Terraform/Pulumi to reduce manual errors by 95%:

```hcl
# Terraform: Provider-level default tags
provider "aws" {
  default_tags {
    tags = {
      Environment = var.environment
      Owner       = var.owner
      CostCenter  = var.cost_center
      Project     = var.project
      ManagedBy   = "terraform"
    }
  }
}
```

All resources automatically inherit these tags. Resource-specific tags merge with defaults.

For complete Terraform, Pulumi, and CloudFormation examples, see `examples/terraform/`, `examples/pulumi/`, and `examples/cloudformation/`.

### Policy-Based Enforcement

Enforce tagging at resource creation time:

**AWS**: Use AWS Config rules to check tag compliance (alert or deny)
**Azure**: Use Azure Policy for tag inheritance and enforcement
**GCP**: Use Organization Policies to restrict label values
**Kubernetes**: Use OPA Gatekeeper or Kyverno for admission control

For enforcement implementation patterns, see `references/enforcement-patterns.md`.

### Tag Compliance Auditing

Run regular audits (weekly recommended) to identify untagged resources:

**AWS Config Query** (SQL):
```sql
SELECT resourceId, resourceType, configuration.tags
WHERE resourceType IN ('AWS::EC2::Instance', 'AWS::RDS::DBInstance')
  AND (configuration.tags IS NULL OR NOT configuration.tags.Environment EXISTS)
```

**Azure Resource Graph Query** (KQL):
```kusto
Resources
| where type in~ ('microsoft.compute/virtualmachines')
| where isnull(tags.Environment) or isnull(tags.Owner)
| project name, type, resourceGroup, tags
```

**GCP Cloud Asset Inventory**:
```bash
gcloud asset search-all-resources \
  --query="NOT labels:environment OR NOT labels:owner" \
  --format="table(nam