Functions Terraform Patterns — REFERENCE ONLY

⛔ DO NOT COPY THIS CODE DIRECTLY

This file contains reference patterns for understanding Azure Functions Terraform structure. You MUST use the composition algorithm to generate infrastructure:

Load templates/selection.md to choose the correct base template

Follow templates/recipes/composition.md for the exact algorithm

Use functions_template_get MCP tool (with infrastructure: "terraform") to list and fetch templates and write functionFiles[] + projectFiles[] directly — NEVER hand-write Bicep/Terraform and use azd init -t <template>/func init/func new as fallback when composing multiple recipes and required templates are not found

Hand-writing Terraform from these patterns will result in missing RBAC, incorrect managed identity configuration, and security vulnerabilities.

Flex Consumption (Recommended)

Use Flex Consumption for new deployments with managed identity (no connection strings).

⚠️ IMPORTANT: Flex Consumption requires azurerm provider v4.2 or later.

terraform {
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~> 4.2"
    }
  }
}

provider "azurerm" {
  features {}
}

resource "azurerm_storage_account" "function_storage" {
  name                     = "${var.resource_prefix}func${var.unique_hash}"
  location                 = var.location
  resource_group_name      = azurerm_resource_group.main.name
  account_tier             = "Standard"
  account_replication_type = "LRS"
  
  min_tls_version              = "TLS1_2"
  allow_nested_items_to_be_public = false
  shared_access_key_enabled    = false  # Enforce managed identity
}

resource "azurerm_storage_container" "deployment_package" {
  name                  = "deploymentpackage"
  storage_account_id    = azurerm_storage_account.function_storage.id
  container_access_type = "private"
}

resource "azurerm_application_insights" "function_insights" {
  name                = "appi-${var.unique_hash}"
  location            = var.location
  resource_group_name = azurerm_resource_group.main.name
  application_type    = "web"
}

resource "azurerm_service_plan" "function_plan" {
  name                = "plan-${var.unique_hash}"
  location            = var.location
  resource_group_name = azurerm_resource_group.main.name
  os_type             = "Linux"
  sku_name            = "FC1"
}

resource "azurerm_linux_function_app" "function_app" {
  name                       = "${var.resource_prefix}-${var.service_name}-${var.unique_hash}"
  location                   = var.location
  resource_group_name        = azurerm_resource_group.main.name
  service_plan_id            = azurerm_service_plan.function_plan.id
  storage_account_name       = azurerm_storage_account.function_storage.name
  storage_uses_managed_identity = true
  https_only                 = true

  identity {
    type = "SystemAssigned"
  }

  function_app_config {
    deployment {
      storage {
        type  = "blob_container"
        value = "${azurerm_storage_account.function_storage.primary_blob_endpoint}${azurerm_storage_container.deployment_package.name}"
        authentication {
          type = "SystemAssignedIdentity"
        }
      }
    }

    scale_and_concurrency {
      maximum_instance_count = 100
      instance_memory_mb     = 2048
    }

    runtime {
      name    = "python"  # or "node", "dotnet-isolated"
      version = "3.11"
    }
  }

  site_config {
    application_insights_connection_string = azurerm_application_insights.function_insights.connection_string
    
    application_stack {
      python_version = "3.11"  # Adjust based on runtime
    }
  }

  app_settings = {
    "AzureWebJobsStorage__blobServiceUri"  = azurerm_storage_account.function_storage.primary_blob_endpoint
    "FUNCTIONS_EXTENSION_VERSION"          = "~4"
    "FUNCTIONS_WORKER_RUNTIME"             = "python"
  }
}

# Grant Function App access to Storage for runtime
resource "azurerm_role_assignment" "function_storage_access" {
  scope                = azurerm_storage_account.function_storage.id
  role_definition_name = "Storage Blob Data Owner"
  principal_id         = azurerm_linux_function_app.function_app.identity[0].principal_id
}

💡 Key Points:

Use AzureWebJobsStorage__blobServiceUri instead of connection string

Set shared_access_key_enabled = false for enhanced security

Use storage_uses_managed_identity = true for deployment authentication

Grant Storage Blob Data Owner role for full access to blobs, queues, and tables

Requires azurerm provider v4.2 or later

Using Azure Verified Module

For production deployments, use the official Azure Verified Module:

module "function_app" {
  source  = "Azure/avm-res-web-site/azurerm"
  version = "~> 0.0"

  name                = "${var.resource_prefix}-${var.service_name}-${var.unique_hash}"
  location            = var.location
  resource_group_name = azurerm_resource_group.main.name
  
  kind    = "functionapp"
  os_type = "Linux"

  sku_name = "FC1"

  function_app_storage_account_name       = azurerm_storage_account.function_storage.name
  function_app_storage_uses_managed_identity = true

  site_config = {
    application_insights_connection_string = azurerm_application_insights.function_insights.connection_string
    
    application_stack = {
      python_version = "3.11"
    }
  }

  app_settings = {
    "AzureWebJobsStorage__blobServiceUri" = azurerm_storage_account.function_storage.primary_blob_endpoint
    "FUNCTIONS_EXTENSION_VERSION"         = "~4"
    "FUNCTIONS_WORKER_RUNTIME"            = "python"
  }

  identity = {
    type = "SystemAssigned"
  }
}

💡 Example Reference: HashiCorp Flex Consumption Example

Consumption Plan (Legacy)

⛔ DO NOT USE — Y1/Dynamic SKU is deprecated for new deployments. ALWAYS use Flex Consumption (FC1) for all new Azure Functions. The Y1 example below is only for reference when migrating legacy apps.

⚠️ Not recommended for new deployments. Use Flex Consumption instead.

💡 OS and Slots Matter for Consumption:

Linux Consumption (os_type = "Linux"): Does not support deployment slots.

Windows Consumption (os_type = "Windows"): Supports 1 staging slot (2 total including production). If a user specifically needs Windows Consumption with a slot, that is supported — use the Windows pattern below. For new apps needing slots, prefer Elastic Premium (EP1) for better performance and no cold-start issues.

Linux Consumption (no slot support)

resource "azurerm_storage_account" "function_storage" {
  name                     = "${var.resource_prefix}func${var.unique_hash}"
  location                 = var.location
  resource_group_name      = azurerm_resource_group.main.name
  account_tier             = "Standard"
  account_replication_type = "LRS"
}

resource "azurerm_service_plan" "function_plan" {
  name                = "${var.resource_prefix}-funcplan-${var.unique_hash}"
  location            = var.location
  resource_group_name = azurerm_resource_group.main.name
  os_type             = "Linux"
  sku_name            = "Y1"
}

resource "azurerm_linux_function_app" "function_app" {
  name                = "${var.resource_prefix}-${var.service_name}-${var.unique_hash}"
  location            = var.location
  resource_group_name = azurerm_resource_group.main.name
  service_plan_id     = azurerm_service_plan.function_plan.id
  https_only          = true
  
  storage_account_name       = azurerm_storage_account.function_storage.name
  storage_account_access_key = azurerm_storage_account.function_storage.primary_access_key
  
  site_config {
    application_insights_connection_string = azurerm_application_insights.function_insights.connection_string
    
    application_stack {
      python_version = "3.11"
    }
  }

  app_settings = {
    "FUNCTIONS_EXTENSION_VERSION" = "~4"
    "FUNCTIONS_WORKER_RUNTIME"    = "python"
  }

  identity {
    type = "SystemAssigned"
  }
}

Windows Consumption (supports 1 staging slot)

⚠️ Windows Consumption is not recommended for new projects — consider Flex Consumption or Elastic Premium. Use this pattern only for existing Windows apps or when Windows-specific features are required.

resource "azurerm_service_plan" "function_plan" {
  name                = "${var.resource_prefix}-funcplan-${var.unique_hash}"
  location            = var.location
  resource_group_name = azurerm_resource_group.main.name
  os_type             = "Windows"
  sku_name            = "Y1"
}

resource "azurerm_windows_function_app" "function_app" {
  name                = "${var.resource_prefix}-${var.service_name}-${var.unique_hash}"
  location            = var.location
  resource_group_name = azurerm_resource_group.main.name
  service_plan_id     = azurerm_service_plan.function_plan.id
  https_only          = true

  storage_account_name       = azurerm_storage_account.function_storage.name
  storage_account_access_key = azurerm_storage_account.function_storage.primary_access_key

  site_config {
    application_insights_connection_string = azurerm_application_insights.function_insights.connection_string
    application_stack {
      node_version = "~20"
    }
  }

  app_settings = {
    "FUNCTIONS_EXTENSION_VERSION"             = "~4"
    "FUNCTIONS_WORKER_RUNTIME"                = "node"
    "WEBSITE_CONTENTSHARE"                    = "${lower(var.service_name)}-prod"  # must differ per slot; Azure Files share names are lowercase
    "WEBSITE_CONTENTAZUREFILECONNECTIONSTRING" = azurerm_storage_account.function_storage.primary_connection_string
  }

  sticky_settings {
    app_setting_names = ["WEBSITE_CONTENTSHARE", "WEBSITE_CONTENTAZUREFILECONNECTIONSTRING"]
  }

  identity {
    type = "SystemAssigned"
  }
}

# 1 staging slot is supported on Windows Consumption
resource "azurerm_windows_function_app_slot" "staging" {
  name            = "staging"
  function_app_id = azurerm_windows_function_app.function_app.id

  storage_account_name       = azurerm_storage_account.function_storage.name
  storage_account_access_key = azurerm_storage_account.function_storage.primary_access_key

  site_config {
    application_insights_connection_string = azurerm_application_insights.function_insights.connection_string
    application_stack {
      node_version = "~20"
    }
  }

  app_settings = {
    "FUNCTIONS_EXTENSION_VERSION"             = "~4"
    "FUNCTIONS_WORKER_RUNTIME"                = "node"
    "WEBSITE_CONTENTSHARE"                    = "${var.service_name}-staging"  # MUST differ from production
    "WEBSITE_CONTENTAZUREFILECONNECTIONSTRING" = azurerm_storage_account.function_storage.primary_connection_string
  }
}

Service Bus Integration (Managed Identity)

data "azurerm_servicebus_namespace" "example" {
  name                = var.servicebus_namespace_name
  resource_group_name = var.servicebus_resource_group
}

resource "azurerm_linux_function_app" "function_app" {
  # ... (Function App definition from above)
  
  app_settings = {
    # Storage with managed identity
    "AzureWebJobsStorage__blobServiceUri" = azurerm_storage_account.function_storage.primary_blob_endpoint
    
    # Service Bus with managed identity
    "SERVICEBUS__fullyQualifiedNamespace" = "${data.azurerm_servicebus_namespace.example.name}.servicebus.windows.net"
    "SERVICEBUS_QUEUE_NAME"               = var.servicebus_queue_name
    
    # Other settings...
    "FUNCTIONS_EXTENSION_VERSION"  = "~4"
    "FUNCTIONS_WORKER_RUNTIME"     = "python"
    "APPLICATIONINSIGHTS_CONNECTION_STRING" = azurerm_application_insights.function_insights.connection_string
  }
}

# Grant Service Bus Data Receiver role for triggers
resource "azurerm_role_assignment" "servicebus_receiver" {
  scope                = data.azurerm_servicebus_namespace.example.id
  role_definition_name = "Azure Service Bus Data Receiver"
  principal_id         = azurerm_linux_function_app.function_app.identity[0].principal_id
}

# Grant Service Bus Data Sender role (if function sends messages)
resource "azurerm_role_assignment" "servicebus_sender" {
  scope                = data.azurerm_servicebus_namespace.example.id
  role_definition_name = "Azure Service Bus Data Sender"
  principal_id         = azurerm_linux_function_app.function_app.identity[0].principal_id
}

💡 Key Points:

Use SERVICEBUS__fullyQualifiedNamespace (double underscore) for managed identity

Grant Service Bus Data Receiver role for reading messages

Grant Service Bus Data Sender role for sending messages (if needed)

Role assignments automatically enable connection via managed identity

Premium Plan (No Cold Starts)

resource "azurerm_service_plan" "function_plan" {
  name                = "${var.resource_prefix}-funcplan-${var.unique_hash}"
  location            = var.location
  resource_group_name = azurerm_resource_group.main.name
  os_type             = "Linux"
  sku_name            = "EP1"  # EP1, EP2, or EP3
}

resource "azurerm_linux_function_app" "function_app" {
  # ... (rest of configuration similar to Flex Consumption)
  
  site_config {
    # Premium-specific settings
    always_on                      = true
    pre_warmed_instance_count      = 1
    elastic_instance_minimum       = 1
    
    application_stack {
      python_version = "3.11"
    }
  }
}

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