Providers & Resources

Learn how Terraform talks to cloud APIs through providers and how resources map directly to real infrastructure objects.

Simple Explanation (ELI5)

Terraform is the planner. Providers are translators for each cloud platform. Resources are the real things Terraform creates, like a resource group, VNet, or AKS cluster.

Technical Explanation

A provider plugin handles API communication and authentication. A resource block describes desired infrastructure Terraform should manage. A data source reads existing values without creating new infrastructure.

terraform {
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~> 4.0"
    }
  }
}

provider "azurerm" {
  features {}
}

Real-World Example: RG + VNet + AKS (Simplified)

This pattern appears in production platform repositories: build a resource group, create network boundaries, then provision AKS into the subnet.

resource "azurerm_resource_group" "platform" {
  name     = "rg-platform-dev"
  location = "eastus"
}

resource "azurerm_virtual_network" "platform" {
  name                = "vnet-platform-dev"
  location            = azurerm_resource_group.platform.location
  resource_group_name = azurerm_resource_group.platform.name
  address_space       = ["10.40.0.0/16"]
}

resource "azurerm_subnet" "aks" {
  name                 = "snet-aks"
  resource_group_name  = azurerm_resource_group.platform.name
  virtual_network_name = azurerm_virtual_network.platform.name
  address_prefixes     = ["10.40.1.0/24"]
}

resource "azurerm_kubernetes_cluster" "platform" {
  name                = "aks-platform-dev"
  location            = azurerm_resource_group.platform.location
  resource_group_name = azurerm_resource_group.platform.name
  dns_prefix          = "aksplatformdev"

  default_node_pool {
    name           = "system"
    node_count     = 2
    vm_size        = "Standard_D4s_v5"
    vnet_subnet_id = azurerm_subnet.aks.id
  }

  identity {
    type = "SystemAssigned"
  }
}

Hands-on

1. Create a resource group resource and apply.
2. Add VNet and subnet resources and run plan again.
3. Add AKS resource and inspect the full dependency graph in plan output.

Troubleshooting

Problem: plan fails even though syntax looks correct.

• Verify provider authentication context (local vs CI).
• Check provider version compatibility with used resource arguments.
• Check subscription and region constraints for requested resource types.

Interview Questions

Summary

Providers define how Terraform communicates. Resources define what Terraform manages. Real platform delivery starts when these blocks are composed into end-to-end infrastructure patterns like RG + VNet + AKS.