Projet 5 : Multi-Environnements

Contexte

Vous devez déployer la même infrastructure sur 3 environnements (dev, staging, production) avec des configurations différentes. L'objectif est de maximiser la réutilisation du code tout en permettant des variations par environnement.

Exigences

Code unique pour tous les environnements
Variables différentes par environnement
State séparé par environnement
Promotion automatisée entre environnements

Stratégies comparées

Option 1 : Terraform Workspaces

Structure

infra-workspaces/
├── main.tf
├── variables.tf
├── outputs.tf
├── versions.tf
├── terraform.tfvars      # Valeurs par défaut
├── envs/
│   ├── dev.tfvars
│   ├── staging.tfvars
│   └── prod.tfvars
└── modules/
    ├── vpc/
    ├── compute/
    └── database/

variables.tf

variable "project_name" {
  description = "Project name"
  type        = string
}

variable "region" {
  description = "AWS Region"
  type        = string
  default     = "eu-west-1"
}

# Configuration par environnement
variable "env_config" {
  description = "Environment-specific configuration"
  type = object({
    vpc_cidr           = string
    instance_type      = string
    min_size           = number
    max_size           = number
    desired_size       = number
    db_instance_class  = string
    multi_az           = bool
    enable_monitoring  = bool
  })
}

main.tf

locals {
  environment = terraform.workspace
  name_prefix = "${var.project_name}-${local.environment}"
  
  # Configuration par défaut + override par workspace
  default_config = {
    dev = {
      vpc_cidr          = "10.1.0.0/16"
      instance_type     = "t3.micro"
      min_size          = 1
      max_size          = 2
      desired_size      = 1
      db_instance_class = "db.t3.micro"
      multi_az          = false
      enable_monitoring = false
    }
    staging = {
      vpc_cidr          = "10.2.0.0/16"
      instance_type     = "t3.small"
      min_size          = 1
      max_size          = 3
      desired_size      = 2
      db_instance_class = "db.t3.small"
      multi_az          = false
      enable_monitoring = true
    }
    production = {
      vpc_cidr          = "10.0.0.0/16"
      instance_type     = "t3.medium"
      min_size          = 2
      max_size          = 10
      desired_size      = 3
      db_instance_class = "db.t3.medium"
      multi_az          = true
      enable_monitoring = true
    }
  }
  
  config = lookup(local.default_config, local.environment, local.default_config["dev"])
}

module "vpc" {
  source = "./modules/vpc"
  
  name_prefix = local.name_prefix
  vpc_cidr    = local.config.vpc_cidr
  environment = local.environment
}

module "compute" {
  source = "./modules/compute"
  
  name_prefix   = local.name_prefix
  vpc_id        = module.vpc.vpc_id
  subnet_ids    = module.vpc.private_subnet_ids
  instance_type = local.config.instance_type
  min_size      = local.config.min_size
  max_size      = local.config.max_size
  desired_size  = local.config.desired_size
  environment   = local.environment
}

module "database" {
  source = "./modules/database"
  
  name_prefix       = local.name_prefix
  vpc_id            = module.vpc.vpc_id
  subnet_ids        = module.vpc.database_subnet_ids
  instance_class    = local.config.db_instance_class
  multi_az          = local.config.multi_az
  security_group_id = module.compute.app_security_group_id
  environment       = local.environment
}

Utilisation des Workspaces

# Créer les workspaces
terraform workspace new dev
terraform workspace new staging
terraform workspace new production

# Lister les workspaces
terraform workspace list

# Sélectionner un workspace
terraform workspace select dev

# Déployer sur dev
terraform workspace select dev
terraform apply -var-file=envs/dev.tfvars

# Déployer sur staging
terraform workspace select staging
terraform apply -var-file=envs/staging.tfvars

# Déployer sur production
terraform workspace select production
terraform apply -var-file=envs/prod.tfvars

Option 2 : Structure par Répertoire

Structure

infra-directories/
├── modules/
│   ├── vpc/
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   └── outputs.tf
│   ├── compute/
│   │   ├── main.tf
│   │   ├── variables.tf
│   │   └── outputs.tf
│   └── database/
│       ├── main.tf
│       ├── variables.tf
│       └── outputs.tf
└── environments/
    ├── dev/
    │   ├── main.tf
    │   ├── backend.tf
    │   └── terraform.tfvars
    ├── staging/
    │   ├── main.tf
    │   ├── backend.tf
    │   └── terraform.tfvars
    └── prod/
        ├── main.tf
        ├── backend.tf
        └── terraform.tfvars

environments/dev/main.tf

module "infrastructure" {
  source = "../../modules"
  
  project_name = "myapp"
  environment  = "dev"
  region       = "eu-west-1"
  
  vpc_cidr          = "10.1.0.0/16"
  instance_type     = "t3.micro"
  min_size          = 1
  max_size          = 2
  desired_size      = 1
  db_instance_class = "db.t3.micro"
  multi_az          = false
}

environments/dev/backend.tf

terraform {
  backend "s3" {
    bucket         = "mycompany-terraform-state"
    key            = "myapp/dev/terraform.tfstate"
    region         = "eu-west-1"
    encrypt        = true
    dynamodb_table = "terraform-locks"
  }
}

environments/prod/main.tf

module "infrastructure" {
  source = "../../modules"
  
  project_name = "myapp"
  environment  = "production"
  region       = "eu-west-1"
  
  vpc_cidr          = "10.0.0.0/16"
  instance_type     = "t3.medium"
  min_size          = 2
  max_size          = 10
  desired_size      = 3
  db_instance_class = "db.t3.medium"
  multi_az          = true
}

Déploiement

# Déployer dev
cd environments/dev
terraform init
terraform apply

# Déployer production
cd ../prod
terraform init
terraform apply

Option 3 : Terragrunt (Recommandé)

Structure

infra-terragrunt/
├── terragrunt.hcl           # Configuration racine
├── modules/
│   └── infrastructure/
│       ├── main.tf
│       ├── variables.tf
│       └── outputs.tf
└── environments/
    ├── terragrunt.hcl       # Configuration partagée
    ├── dev/
    │   └── terragrunt.hcl
    ├── staging/
    │   └── terragrunt.hcl
    └── prod/
        └── terragrunt.hcl

terragrunt.hcl (racine)

# Configuration du backend S3 (DRY)
remote_state {
  backend = "s3"
  generate = {
    path      = "backend.tf"
    if_exists = "overwrite_terragrunt"
  }
  config = {
    bucket         = "mycompany-terraform-state"
    key            = "${path_relative_to_include()}/terraform.tfstate"
    region         = "eu-west-1"
    encrypt        = true
    dynamodb_table = "terraform-locks"
  }
}

# Générer le provider
generate "provider" {
  path      = "provider.tf"
  if_exists = "overwrite_terragrunt"
  contents  = <<EOF
provider "aws" {
  region = var.region
  
  default_tags {
    tags = {
      Environment = var.environment
      ManagedBy   = "Terragrunt"
      Project     = var.project_name
    }
  }
}
EOF
}

environments/terragrunt.hcl

# Inclure la config racine
include "root" {
  path = find_in_parent_folders()
}

# Variables communes à tous les environnements
locals {
  project_name = "myapp"
  region       = "eu-west-1"
}

inputs = {
  project_name = local.project_name
  region       = local.region
}

environments/dev/terragrunt.hcl

include "root" {
  path = find_in_parent_folders()
}

include "env" {
  path = "${dirname(find_in_parent_folders())}/environments/terragrunt.hcl"
}

terraform {
  source = "${dirname(find_in_parent_folders())}/modules/infrastructure"
}

inputs = {
  environment       = "dev"
  vpc_cidr          = "10.1.0.0/16"
  instance_type     = "t3.micro"
  min_size          = 1
  max_size          = 2
  desired_size      = 1
  db_instance_class = "db.t3.micro"
  multi_az          = false
  enable_monitoring = false
}

environments/prod/terragrunt.hcl

include "root" {
  path = find_in_parent_folders()
}

include "env" {
  path = "${dirname(find_in_parent_folders())}/environments/terragrunt.hcl"
}

terraform {
  source = "${dirname(find_in_parent_folders())}/modules/infrastructure"
}

# Dépendances (promotion depuis staging)
dependencies {
  paths = ["../staging"]
}

dependency "staging" {
  config_path = "../staging"
  
  mock_outputs = {
    vpc_id = "vpc-mock"
  }
}

inputs = {
  environment       = "production"
  vpc_cidr          = "10.0.0.0/16"
  instance_type     = "t3.medium"
  min_size          = 2
  max_size          = 10
  desired_size      = 3
  db_instance_class = "db.t3.medium"
  multi_az          = true
  enable_monitoring = true
  
  # Utiliser une référence de staging si nécessaire
  # staging_vpc_id = dependency.staging.outputs.vpc_id
}

Commandes Terragrunt

# Déployer un environnement
cd environments/dev
terragrunt apply

# Déployer tous les environnements
cd environments
terragrunt run-all apply

# Plan sur tous les environnements
terragrunt run-all plan

# Destroy un environnement
cd environments/dev
terragrunt destroy

Variables par environnement (Détail)

Module principal - variables.tf

variable "environment" {
  description = "Environment name"
  type        = string
  
  validation {
    condition     = contains(["dev", "staging", "production"], var.environment)
    error_message = "Environment must be dev, staging, or production."
  }
}

# Utiliser des maps pour des valeurs par environnement
locals {
  env_settings = {
    dev = {
      deletion_protection = false
      backup_retention    = 1
      log_retention       = 7
      alarm_threshold     = 90
    }
    staging = {
      deletion_protection = false
      backup_retention    = 7
      log_retention       = 14
      alarm_threshold     = 85
    }
    production = {
      deletion_protection = true
      backup_retention    = 30
      log_retention       = 90
      alarm_threshold     = 80
    }
  }
  
  settings = local.env_settings[var.environment]
}

Comparaison des approches

Critère	Workspaces	Directories	Terragrunt
Simplicité	⭐⭐⭐	⭐⭐	⭐
Séparation state	⭐⭐	⭐⭐⭐	⭐⭐⭐
DRY	⭐⭐⭐	⭐	⭐⭐⭐
CI/CD	⭐⭐	⭐⭐⭐	⭐⭐⭐
Sécurité	⭐	⭐⭐⭐	⭐⭐⭐
Courbe apprentissage	Facile	Moyen	Difficile

Recommandation

Petits projets : Workspaces
Projets moyens : Structure par répertoire
Projets complexes : Terragrunt

Bonnes pratiques

1. Nommage cohérent

locals {
  name_prefix = "${var.project_name}-${var.environment}"
  
  common_tags = {
    Project     = var.project_name
    Environment = var.environment
    ManagedBy   = "Terraform"
    CostCenter  = var.cost_center
  }
}

2. Validation des environnements

resource "null_resource" "validate_prod" {
  count = var.environment == "production" ? 1 : 0
  
  lifecycle {
    precondition {
      condition     = var.multi_az == true
      error_message = "Production must have multi_az enabled."
    }
    
    precondition {
      condition     = var.backup_retention >= 7
      error_message = "Production must have at least 7 days backup retention."
    }
  }
}

3. Outputs par environnement

output "environment_info" {
  value = {
    environment  = var.environment
    vpc_id       = module.vpc.vpc_id
    api_endpoint = module.api.endpoint
    db_endpoint  = var.environment != "dev" ? module.database.endpoint : "N/A"
  }
}

← Projet 4 | Projet 6: Pipeline CI/CD →

Contexte​

Exigences​

Stratégies comparées​

Option 1 : Terraform Workspaces​

Structure​

variables.tf​

main.tf​

Utilisation des Workspaces​

Option 2 : Structure par Répertoire​

Structure​

environments/dev/main.tf​

environments/dev/backend.tf​

environments/prod/main.tf​

Déploiement​

Option 3 : Terragrunt (Recommandé)​

Structure​

terragrunt.hcl (racine)​

environments/terragrunt.hcl​

environments/dev/terragrunt.hcl​

environments/prod/terragrunt.hcl​

Commandes Terragrunt​

Variables par environnement (Détail)​

Module principal - variables.tf​

Comparaison des approches​

Bonnes pratiques​

1. Nommage cohérent​

2. Validation des environnements​

3. Outputs par environnement​

Contexte

Exigences

Stratégies comparées

Option 1 : Terraform Workspaces

Structure

variables.tf

main.tf

Utilisation des Workspaces

Option 2 : Structure par Répertoire

Structure

environments/dev/main.tf

environments/dev/backend.tf

environments/prod/main.tf

Déploiement

Option 3 : Terragrunt (Recommandé)

Structure

terragrunt.hcl (racine)

environments/terragrunt.hcl

environments/dev/terragrunt.hcl

environments/prod/terragrunt.hcl

Commandes Terragrunt

Variables par environnement (Détail)

Module principal - variables.tf

Comparaison des approches

Bonnes pratiques

1. Nommage cohérent

2. Validation des environnements

3. Outputs par environnement