Azure App Configuration - Conditionally create feature flag using bicep

Question

I plan to use the Feature Management functionality within Azure App Configuration service.

Using bicep I create the configuration store.

Template: https://learn.microsoft.com/en-us/azure/templates/microsoft.appconfiguration/2021-10-01-preview/configurationstores?tabs=bicep.

Using bicep I add a feature flag.

Template: https://learn.microsoft.com/en-us/azure/templates/microsoft.appconfiguration/2021-10-01-preview/configurationstores/keyvalues?tabs=bicep.

The value should be initially set to false and once available it's up to the business/ops to change the value to true in the Azure Portal.

So I'm looking for a way to conditionally create the feature flag in my bicep; create the feature flag if it not exists. When it already exists, the bicep should skip creation because it could otherwise overwrite/reset the flag value changed by the business/ops.

I found this issue on GitHub from which I conclude that bicep does not yet support this requirement: https://github.com/Azure/bicep/issues/4023

Any suggestions for a workaround?

Thomas · Accepted Answer · 2022-10-13T07:15:37.993

You can't really do that unless you check manually if the featureFlag exists before running the deployment. ARM templates (and Bicep) try to be idempotent so if you apply the same template multiple times it will reset any manual changes.

Here is a bicep file that creates a config store and feature flag:

// main.bicep
param location string = resourceGroup().location
param configurationStoreName string
param featureFlagExists bool
param featureFlagName string

// Create the configuration store
resource configurationStore 'Microsoft.AppConfiguration/configurationStores@2021-10-01-preview' = {
  name: configurationStoreName
  location: location
  sku: {
    name: 'free'
  }
  properties: {
    disableLocalAuth: false
    enablePurgeProtection: false
    encryption: {}
    softDeleteRetentionInDays: 0
  }
}

// Only create the feature flag if not exists
resource featureFlag 'Microsoft.AppConfiguration/configurationStores/keyValues@2021-10-01-preview' = if (!featureFlagExists) {
  name: '.appconfig.featureflag~2F${featureFlagName}'
  parent: configurationStore
  properties: {
    contentType: 'application/vnd.microsoft.appconfig.ff+json;charset=utf-8'
    tags: {}
    value: '{"id": "${featureFlagName}", "description": "", "enabled": false, "conditions": {"client_filters":[]}}'
  }
}

And here is a sample powershell script that invoke it:

check if the config store exists
check if the feature flag exists
run the deployment

$resourceGroupName = "<resource group name>"
$configurationStoreName = "<config store name>"
$featureFlagName = "<feature flag name>"

# Check if the app configuration exists
$appConfigExists = (az appconfig list `
    --resource-group $resourceGroupName `
    --query "[?name=='$configurationStoreName'].id" `
| ConvertFrom-Json).Length -gt 0

# Check if the feature flag exists
$featureFlagExists = $false
if ($appConfigExists) {
  $featureFlagExists = (az appconfig kv list `
      --name $configurationStoreName `
      --query "[?key=='.appconfig.featureflag/$featureFlagName'].key" `
  | ConvertFrom-Json).Length -gt 0
}

az deployment group create `
  --resource-group $resourceGroupName `
  --template-file .\main.bicep `
  --parameters `
  configurationStoreName=$configurationStoreName `
  featureFlagExists=$featureFlagExists `
  featureFlagName=$featureFlagName

Azure App Configuration - Conditionally create feature flag using bicep

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