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Kenichiro Nakamura
Kenichiro Nakamura

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Bicep: Deploy Function App with VNET integration

#azure #bicep #vnet #functions

Virtual Network Integration feature is important to secure ingress/egress of Function App. See Azure Functions networking options for more detail.

In this article, I explain how we can deploy such configuration via bicep.

Basic bicep

I use Quickstart: Create and deploy Azure Functions resources using Bicep as base script.

Add VNET section

Firstly, we need VNET to use VNET integration. So I added following code before creating storage account.

  • We need to set delegation to support VNET integration. Set it for Microsoft.Web/serverFarms. See What is subnet delegation? for detail. 
var vnetName = 'vnet-${appName}'
var subnetNeme = 'snet-${appName}'
resource vnet 'Microsoft.Network/virtualNetworks@2021-08-01' = {
  name: vnetName
  location: location
  properties: {
    addressSpace: {
      addressPrefixes: [
        '10.0.0.0/16'
      ]
    }
    subnets: [
      {
        name: subnetNeme
        properties: {
          addressPrefix: '10.0.0.0/24'
          delegations: [
            {
              name: 'Microsoft.Web/serverFarms'
              properties: {
                serviceName: 'Microsoft.Web/serverFarms'
              }
            }
          ]
        }
      }
    ]
  }
}
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Change SKU

Serverless plan doesn't support VNET Integration, so I changed SKU to Standard for hosting plan.

resource hostingPlan 'Microsoft.Web/serverfarms@2021-03-01' = {
  name: hostingPlanName
  location: location
  sku: {
    name: 'S1'
    tier: 'Standard'
  }
  properties: {}
}
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Add VNET info

Finally, I added virtualNetworkSubnetId property for functionApp.

resource functionApp 'Microsoft.Web/sites@2021-03-01' = {
  name: functionAppName
  location: location
  kind: 'functionapp'
  identity: {
    type: 'SystemAssigned'
  }
  properties: {
    virtualNetworkSubnetId: vnet.properties.subnets[0].id
    serverFarmId: hostingPlan.id
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Complete Bicep 

@description('The name of the function app that you wish to create.')
param appName string = 'fnapp${uniqueString(resourceGroup().id)}'

@description('Storage Account type')
@allowed([
  'Standard_LRS'
  'Standard_GRS'
  'Standard_RAGRS'
])
param storageAccountType string = 'Standard_LRS'

@description('Location for all resources.')
param location string = resourceGroup().location

@description('Location for Application Insights')
param appInsightsLocation string

@description('The language worker runtime to load in the function app.')
@allowed([
  'node'
  'dotnet'
  'java'
])
param runtime string = 'node'

var functionAppName = appName
var hostingPlanName = appName
var applicationInsightsName = appName
var vnetName = 'vnet-${appName}'
var subnetNeme = 'snet-${appName}'
var storageAccountName = '${uniqueString(resourceGroup().id)}azfunctions'
var functionWorkerRuntime = runtime

resource vnet 'Microsoft.Network/virtualNetworks@2021-08-01' = {
  name: vnetName
  location: location
  properties: {
    addressSpace: {
      addressPrefixes: [
        '10.0.0.0/16'
      ]
    }
    subnets: [
      {
        name: subnetNeme
        properties: {
          addressPrefix: '10.0.0.0/24'
          delegations: [
            {
              name: 'Microsoft.Web/serverFarms'
              properties: {
                serviceName: 'Microsoft.Web/serverFarms'
              }
            }
          ]
        }
      }
    ]
  }
}

resource storageAccount 'Microsoft.Storage/storageAccounts@2021-08-01' = {
  name: storageAccountName
  location: location
  sku: {
    name: storageAccountType
  }
  kind: 'Storage'
}

resource hostingPlan 'Microsoft.Web/serverfarms@2021-03-01' = {
  name: hostingPlanName
  location: location
  sku: {
    name: 'S1'
    tier: 'Standard'
  }
  properties: {}
}

resource functionApp 'Microsoft.Web/sites@2021-03-01' = {
  name: functionAppName
  location: location
  kind: 'functionapp'
  identity: {
    type: 'SystemAssigned'
  }
  properties: {
    virtualNetworkSubnetId: vnet.properties.subnets[0].id
    serverFarmId: hostingPlan.id
    siteConfig: {
      appSettings: [
        {
          name: 'AzureWebJobsStorage'
          value: 'DefaultEndpointsProtocol=https;AccountName=${storageAccountName};EndpointSuffix=${environment().suffixes.storage};AccountKey=${storageAccount.listKeys().keys[0].value}'
        }
        {
          name: 'WEBSITE_CONTENTAZUREFILECONNECTIONSTRING'
          value: 'DefaultEndpointsProtocol=https;AccountName=${storageAccountName};EndpointSuffix=${environment().suffixes.storage};AccountKey=${storageAccount.listKeys().keys[0].value}'
        }
        {
          name: 'WEBSITE_CONTENTSHARE'
          value: toLower(functionAppName)
        }
        {
          name: 'FUNCTIONS_EXTENSION_VERSION'
          value: '~2'
        }
        {
          name: 'WEBSITE_NODE_DEFAULT_VERSION'
          value: '~10'
        }
        {
          name: 'APPINSIGHTS_INSTRUMENTATIONKEY'
          value: applicationInsights.properties.InstrumentationKey
        }
        {
          name: 'FUNCTIONS_WORKER_RUNTIME'
          value: functionWorkerRuntime
        }
      ]
      ftpsState: 'FtpsOnly'
      minTlsVersion: '1.2'
    }
    httpsOnly: true
  }
}

resource applicationInsights 'Microsoft.Insights/components@2020-02-02' = {
  name: applicationInsightsName
  location: appInsightsLocation
  kind: 'web'
  properties: {
    Application_Type: 'web'
    Request_Source: 'rest'
  }
}
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Result

Image description

Hope this helps me in the future!

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