Identifying Functions Inside Function Apps

In our previous article Identifying Workflows Inside Azure Logic Apps, we explored how to identify workflows running within Azure Logic Apps across different instances in an Azure tenant. That script allowed us to automate the process of retrieving workflow details such as name, helping with resource management and assesment. By leveraging PowerShell, we eliminated the need for manual tracking through the Azure portal and streamlined the reporting process. By the way as for now, there is no easy way to get this information from Azure Portal.

That approach was particularly useful for Logic Apps Standard, which can host multiple workflows within a single instance. By automating the data retrieval, we generated structured reports showing which workflows were running on which Logic Apps, making it easier to audit and optimize resources.

Identifying Functions Inside Function Apps

Along with Logic App Reports Script, this time we’re applying a similar approach—but for Azure Function Apps! Instead of tracking workflows in Logic Apps, we’ll now focus on Function Apps and the functions running inside them. This report will help you identify all functions deployed across your Azure subscriptions, providing insights into their language runtime, last modified time, and state (enabled/disabled).

Azure Function Apps can host multiple functions within a single instance, just like Logic Apps Standard can host multiple workflows. If you’re working with*serverless computing, keeping track of these functions is crucial, whether for monitoring, debugging, or cost management.

In this article, we will:

✅ Identify all Function Apps within your Azure subscriptions.
✅ Retrieve a list of functions running inside each Function App.
✅ Extract key details such as language runtime, last modified time, and state (enabled/disabled).
✅ Generate a structured CSV report for further analysis.

🔧 Querying Function Apps and Functions Using PowerShell

To achieve this, we will use Azure PowerShell and Azure REST APIs to retrieve all Function Apps in our tenant and list the functions running inside them. Below is a script that scans all subscriptions, collects relevant function details, and exports them into a CSV report for analysis.

# Retrieve all subscriptions
$subscriptions = Get-AzSubscription

# Initialize arrays to store output data
$functionAppsOutput = @()
$functionsOutput = @()

# Loop through each subscription
ForEach ($subscription in $subscriptions) {
    
    Write-Host "Processing subscription: $($subscription.Name)" -ForegroundColor Cyan

    # Set the context to the current subscription
    Set-AzContext -Subscription $subscription.Id

    # Retrieve all Function Apps in the subscription
    $functionApps = Get-AzFunctionApp

    # Loop through each Function App
    ForEach ($functionApp in $functionApps) {

        Write-Host "Processing Function App: $($functionApp.Name)" -ForegroundColor Green

        # Prepare the Function App object
        $functionAppObj = [PSCustomObject]@{
            SubscriptionName    = $subscription.Name
            SubscriptionId      = $subscription.Id
            ResourceGroupName   = $functionApp.ResourceGroup
            FunctionAppName     = $functionApp.Name
            Location            = $functionApp.Location
            AppServicePlanId    = $functionApp.ServerFarmId
            Kind                = $functionApp.Kind
            State               = $functionApp.State
            DefaultHostName     = $functionApp.DefaultHostName
            Enabled             = $functionApp.Enabled
        }

        # Add to Function Apps output array
        $functionAppsOutput += $functionAppObj

        # Prepare REST API URL to list functions within the Function App
        $resourceGroupName = $functionApp.ResourceGroup
        $functionAppName = $functionApp.Name
        $subscriptionId = $subscription.Id

        $url = "https://management.azure.com/subscriptions/$subscriptionId/resourceGroups/$resourceGroupName/providers/Microsoft.Web/sites/$functionAppName/functions?api-version=2022-03-01"

        try {
            # Invoke REST API to get function details
            $response = Invoke-AzRestMethod -Method GET -Uri $url

            if ($response.Content -ne $null) {
                $functions = ($response.Content | ConvertFrom-Json).value

                if ($functions.Count -gt 0) {
                    # Loop through each function
                    ForEach ($function in $functions) {
                        $functionObj = [PSCustomObject]@{
                            SubscriptionName    = $subscription.Name
                            SubscriptionId      = $subscription.Id
                            ResourceGroupName   = $resourceGroupName
                            FunctionAppName     = $functionAppName
                            FunctionName        = $function.properties.name
                            Language            = $function.properties.language
                            LastModified        = $function.properties.lastModifiedTimeUtc
                            IsDisabled          = $function.properties.isDisabled
                            EntryPoint          = $function.properties.entryPoint
                        }

                        # Add to functions output array
                        $functionsOutput += $functionObj
                    }
                } else {
                    # No functions found in this Function App
                    $functionsOutput += [PSCustomObject]@{
                        SubscriptionName    = $subscription.Name
                        SubscriptionId      = $subscription.Id
                        ResourceGroupName   = $resourceGroupName
                        FunctionAppName     = $functionAppName
                        FunctionName        = "No Functions Found"
                        Language            = ""
                        LastModified        = ""
                        IsDisabled          = ""
                        EntryPoint          = ""
                    }
                }
            } else {
                # Unable to retrieve functions
                $functionsOutput += [PSCustomObject]@{
                    SubscriptionName    = $subscription.Name
                    SubscriptionId      = $subscription.Id
                    ResourceGroupName   = $resourceGroupName
                    FunctionAppName     = $functionAppName
                    FunctionName        = "Unable to retrieve functions"
                    Language            = ""
                    LastModified        = ""
                    IsDisabled          = ""
                    EntryPoint          = ""
                }
            }
        }
        catch {
            Write-Warning "Failed to retrieve functions for Function App: $functionAppName"
            $functionsOutput += [PSCustomObject]@{
                SubscriptionName    = $subscription.Name
                SubscriptionId      = $subscription.Id
                ResourceGroupName   = $resourceGroupName
                FunctionAppName     = $functionAppName
                FunctionName        = "Error retrieving functions"
                Language            = ""
                LastModified        = ""
                IsDisabled          = ""
                EntryPoint          = ""
            }
        }
    }
}

# Generate unique filenames with timestamp
$timestamp = Get-Date -Format "yyyyMMdd-HHmmss"

# Export Function Apps report to CSV
$functionAppsFileName = "FunctionApps-Report-$timestamp.csv"
Write-Output "INFO: Exporting Function Apps to CSV file: $functionAppsFileName"
$functionAppsOutput | Export-Csv -Path "$PSScriptRoot\$functionAppsFileName" -NoTypeInformation -Force

# Export Functions report to CSV
$functionsFileName = "Functions-Report-$timestamp.csv"
Write-Output "INFO: Exporting Functions to CSV file: $functionsFileName"
$functionsOutput | Export-Csv -Path "$PSScriptRoot\$functionsFileName" -NoTypeInformation -Force

---

📊 Understanding the Report Output

🔹 Function Apps Report (FunctionApps-Report-YYYYMMDD-HHmmss.csv)
Contains details of all Function Apps, including state, location, and enabled status.

🔹 Functions Report (Functions-Report-YYYYMMDD-HHmmss.csv)
Lists all functions running inside each Function App, with key details like language runtime, modification time, and entry point.

Example Function Apps Report:

SubscriptionName	SubscriptionId	ResourceGroupName	FunctionAppName	Location	AppServicePlanId	Kind	State	DefaultHostName	Enabled
Subscription-1	d068fd18-094c-4b7c-b3d4-6efbbfa5424b	resource-group-1	function-app-1	UK South	/subscriptions/a8689dae-f56e-48ad-a607-542eb0f20acb/resourceGroups/resource-group-1/providers/Microsoft.Web/serverfarms/function-plan-1	functionapp	Running	function-app-1.azurewebsites.net	True
Subscription-2	7fe0317a-0b6a-4ffa-b187-279a59475640	resource-group-2	function-app-2	UK West	/subscriptions/485b419b-6e18-4275-91b3-0647a48b914b/resourceGroups/resource-group-2/providers/Microsoft.Web/serverfarms/function-plan-2	functionapp	Running	function-app-2.azurewebsites.net	True

Example Functions Report:

SubscriptionName	SubscriptionId	ResourceGroupName	FunctionAppName	FunctionName	Language	LastModified	IsDisabled	EntryPoint
Subscription-1	9d6ec9f1-49ba-445c-9a2c-a0f78f786e7c	resource-group-1	function-app-1	ProcessData	DotNet	2024-07-15T10:00:00Z	False	Main.Process
Subscription-2	c6cd29d9-a534-4caa-ab97-5d37c5dbf6b3	resource-group-2	function-app-2	HandleQueueMessage	Python	2024-07-16T12:45:00Z	False	handler.main

🚀 Next Steps

This script automates Function App monitoring just like we did for Logic Apps workflows before. If you have additional requirements—such as checking execution history or filtering by runtime—you can extend this script further!