Web App

Overview

The Web App builder is used to create Azure App Service accounts. It abstracts the Service Plan into the same component, and will also create and configure a linked App Insights resource. If you wish to create a website that connects to an existing service plan or Web App, use the link_to_service_plan keyword and provide the resource name of the service plan or Web App to connect to.

• Web Site (Microsoft.Web/sites)
• Server Farms (Microsoft.Web/serverfarms)
• Source Controls (Microsoft.Web/sites/sourcecontrols)
• Application Insights (Microsoft.Insights/components)

Web App Builder Keywords

Farmer also comes with a dedicated Service Plan builder that contains all of the above keywords that apply to a Service Plan.

Use this builder if you wish to have an explicit and clear separation between your web app and service plan. Otherwise, it is recommended to use the service plan keywords that exist directly in the web app builder, and let Farmer handle the connections between them.

Post-deployment Builder Keywords

The Web App builder contains special commands that are executed after the ARM deployment is completed.

Configuration Members

Key Vault integration

The Web App builder comes with special integration into KeyVault. By activating KeyVault integration, the web app builder can automatically link to, or even create, a full KeyVault instance. All Secret or ARM Expression-based Settings (e.g. a setting that links to the Key of a Storage Account) will automatically be redirected to KeyVault. The value will be stored in KeyVault and the system identity will be activated and provided into the KeyVault with GET permissions. Lastly, Web App app settings will remain in place, using the Azure App Service built-in KeyVault redirection capabilities.

The following keywords exist on the web app:

Virtual Applications virtualApplication

Virtual applications can be defined for a webapp which allows you to specify alternative directories for the application executables or enable a single web app to host multiple applications at once. By default, the following virtualApplication is provided for you:

virtualApplication {
    virtual_path "/"
    physical_path "wwwroot"
}

Examples

A basic web application.

open Farmer
open Farmer.Builders
open Farmer.WebApp

let myWebApp = webApp {
    name "myWebApp"
    service_plan_name "myServicePlan"
    setting "myKey" "aValue"
    sku WebApp.Sku.B1
    always_on
    app_insights_off
    worker_size Medium
    number_of_workers 3
    run_from_package
    system_identity
}

Using a managed Key Vault instance with automatic secret mapping.

open Farmer
open Farmer.Builders

// Create a basic storage account
let data = storageAccount {
    name "mystorage"
}

// Create a web application with a sensitive setting of storage key and an explicit "secret" setting
// which will be passed through by ARM parameter.
let wa = webApp {
    name "isaac"
    setting "key" "value"
    setting "storagekey" data.Key
    link_to_keyvault (ResourceName "isaacvault")
}

// Create a key vault instance and explicitly grant the web application access to it.
let v = keyVault {
    name "isaacvault"
    add_access_policy (AccessPolicy.create (wa.SystemIdentity.PrincipalId, [ KeyVault.Secret.Get; KeyVault.Secret.List ]))
}

Serving two applications simultaneously (a frontend and a backend) from one web app using virtual applications.

open Farmer
open Farmer.Builders

let wa = webApp {
    name "my-site-with-api"
    always_on
    add_virtual_applications [
        virtualApplication {
            virtual_path "/"
            physical_path "frontend" 
        }
        virtualApplication {
            virtual_path "/api"
            physical_path "backend"
            preloaded
        }
    ]
}