Get Webhook url of a Function App in ARM to use for Event Grid Subscription

Question

I am trying to automate the deployment of our environment vir ARM templates. I can deploy Event Grid and Function Apps but now I need to subscribe the function app to the Event Grid after the function app is deployed. Is there a way to get the webhook url for the function app

1. Via a ARM
2. Some other component (Powershell) in the Release pipeline

We are able to create the subscription via ARM once we have the webhook url - but to get to the correct url seems to be where we are falling of the boat.

Any help please

Answer 1

I managed to get this working with the help of the answers from @Van and @Barrie above.

This script returns the masterkey and defaultkey from the azure api, which enables you to create an eventgrid subscription from a functionApp/webApp in your release pipeline.

Van's script (30 Jul) worked with FA version 1 but it did not work for FunctionApps V2 (something was changed in the api). When using this script in V2 the error was:

Runtime keys are stored on blob storage. This API doesn't support this configuration. Please change Environment variable AzureWebJobsSecretStorageType value to 'Files'.

I amended this script and now it works with V2:

#DEBUG: when debugging (running in powershell on local pc) you need to comment out the next line by starting the line with #
param($resourceGroupName, $webAppname)

function Get-PublishingProfileCredentials($resourceGroupName, $webAppName){
        $resourceType = "Microsoft.Web/sites/config"
        $resourceName = "$webAppName/publishingcredentials"
        $publishingCredentials = Invoke-AzureRmResourceAction -ResourceGroupName $resourceGroupName -ResourceType $resourceType -ResourceName $resourceName -Action list -ApiVersion 2015-08-01 -Force
        return $publishingCredentials
}

function Get-KuduApiAuthorisationHeaderValue($resourceGroupName, $webAppName){
        $publishingCredentials = Get-PublishingProfileCredentials $resourceGroupName $webAppName
        return ("Basic {0}" -f [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(("{0}:{1}" -f $publishingCredentials.Properties.PublishingUserName, $publishingCredentials.Properties.PublishingPassword))))
}

function Get-MasterAPIKey($kuduApiAuthorisationToken, $webAppName ){    
        $bearerToken = Invoke-RestMethod -Uri https://$webAppName.scm.azurewebsites.net/api/functions/admin/token  -Headers @{"Authorization"=$kuduApiAuthorisationToken;"If-Match"="*"} 

        $masterkeyResponse = Invoke-RestMethod -Method GET -Headers @{Authorization=("Bearer {0}" -f $bearerToken)} -Uri "https://$webAppName.azurewebsites.net/admin/host/systemkeys/_master" 
        $masterKeyValue = $masterkeyResponse.value
        return $masterKeyValue
}

function Get-HostAPIKeys($kuduApiAuthorisationToken, $webAppName, $masterKey ){
        $apiUrl = "https://$webAppName.azurewebsites.net/admin/host/keys?code=$masterKey"
        $result = Invoke-WebRequest $apiUrl
        return $result
}

#DEBUG: when debugging this in powershell on my local pc I use this to authenticate (remove # to uncomment the next line):
#Login-AzureRmAccount -SubscriptionName "Insert_Subscription_Name_Here"


#DEBUG: when debugging you need to set these parameters:
# $resourceGroupName = "Insert_ResourceGroup_Name_Here"
# $webAppname = "Insert_FunctionApp_Name_Here"


#Auth Header
$kuduToken = Get-KuduApiAuthorisationHeaderValue $resourceGroupName $webAppName

#MasterKey
$masterKey = Get-MasterAPIKey $kuduToken $webAppName
Write-Host "masterKey = " $masterKey

#Default Key
$result = Get-HostAPIKeys $kuduToken $webAppName $masterkey
$keysCode =  $result.Content | ConvertFrom-Json
Write-Host "default Key = " $keysCode.Keys[0].Value

#Set Return Values:
$faMasterKey = $masterkey
$faDefaultKey = $keysCode.Keys[0].Value

Write-Output ("##vso[task.setvariable variable=fa_MasterKey;]$faMasterKey")
Write-Output ("##vso[task.setvariable variable=fa_DefaultKey;]$faDefaultKey")

There is only a small difference between this script and Van's script. The major difference is that this script will work on Azure CLI Functions V2. More info: https://docs.microsoft.com/en-us/azure/azure-functions/functions-bindings-event-grid