In this comprehensive article, I’ll walk you through everything you need to know about Functions_Extension_Version – from basic concepts to advanced implementation strategies.
Table of Contents
Functions_Extension_Version
What is FUNCTIONS_EXTENSION_VERSION?
Functions_Extension_Version is an application setting that determines which version of the Azure Functions runtime your function app uses. This setting is crucial because it:
- Controls which language features are available
- Determines API compatibility
- Affects performance characteristics
- Influences the security posture
This setting lets you target specific runtime versions for each function app in your environment.
By using this settings, you can target a particular version for your Azure Function App. You can also use it to update the version of your Azure Function to a previous or current version.
Available Runtime Versions
Below are the major Azure Functions runtime versions
| Version | Status | Key Features | Support Status |
|---|---|---|---|
| ~4 | Current | Enhanced performance, expanded language support | Fully supported |
| ~3 | Legacy | .NET Core 3.1 support | End of extended support |
| ~2 | Legacy | .NET Core 2.x support | End of extended support |
| ~1 | Legacy | .NET Framework support | End of extended support |
How to Check Your Current Runtime Version
Before making changes, let’s verify which runtime version our function app is using
Approach-1 Using Azure Portal
- Navigate to your function app in the Azure portal
- Select “Configuration” from the left menu
- Look for the
FUNCTIONS_EXTENSION_VERSIONSetting under Application Settings as shown in the screenshot below.
Approach-2 Using Azure CLI
We can execute the following Azure CLI command for the same purpose
az functionapp config appsettings list --name <FUNCTION_APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --query "[?name=='FUNCTIONS_EXTENSION_VERSION']"Setting the Runtime Version
There are several methods to set or update your Azure FUNCTIONS_EXTENSION_VERSION. Let’s explore each approach
Approach 1: Using Azure Portal
- Log in to the Azure Portal (https://portal.azure.com/)
- Navigate to the Azure Function App, click on the configuration from the left navigation, and then click FUNCTIONS_EXTENSION_VERSION.
3. Once you click on that, you can change the FUNCTIONS_EXTENSION_VERSION value and then click on the OK button as shown below
4. Next, click the Save button on the Application settings page to apply the changes.
Approach 2: Using PowerShell
We can also use the below Azure PowerShell command to update or change the Azure function functions_extension_version.
Update-AzFunctionAppSetting -Name <FUNCTION_APP_NAME> -ResourceGroupName <RESOURCE_GROUP_NAME> -AppSetting @{"FUNCTIONS_EXTENSION_VERSION" = "~4"}Example
I am executing the Azure PowerShell command below to update the Azure Functions extension version to “~4”.
Update-AzFunctionAppSetting -Name azurelessons -ResourceGroupName myresgrp -AppSetting @{"FUNCTIONS_EXTENSION_VERSION" = "~4"}After executing the above query, I got the expected output as per the screenshot below.
Approach 3: Using Azure CLI
We can also execute the Azure CLI command for the same purpose.
az functionapp config appsettings set --name <FUNCTION_APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --settings FUNCTIONS_EXTENSION_VERSION="~4"Example
Let me execute the below Azure CLI command to update the runtime version of my Azure Function to “~4”.
az functionapp config appsettings set --name azurelessons --resource-group myresgrp --settings FUNCTIONS_EXTENSION_VERSION="~4"After executing the above query, I obtained the expected output, as shown in the screenshot below.
Best Practices
Based on my experience managing enterprise-scale Azure Functions deployments, here are my recommended best practices:
1. Test Before Upgrading
Always test your functions on the new runtime version in a non-production environment before upgrading production. Create a staging slot with the latest version and validate functionality.
2. Implement Consistent Version Control
Use infrastructure-as-code tools to ensure consistent runtime versions across environments. This prevents the “it works on my machine” syndrome.
3. Monitor Release Notes
Stay informed about new runtime versions through the Azure Updates blog and plan upgrades accordingly.
4. Document Version Dependencies
Maintain documentation on which runtime version each function app requires, including any special dependencies.
Wrapping Up
Managing the FUNCTIONS_EXTENSION_VERSION setting is a fundamental aspect of Azure Functions. By understanding the available options and implementing the strategies outlined in this article, you can ensure that your Azure Function remains secure, performs well, and receives ongoing support.
Remember that staying current with runtime versions isn’t just a maintenance task—it’s an opportunity to utilize the new features and improvements that can enhance your applications.
You may also like the following articles.
- Create a Function App in Azure Portal
- Create Azure Functions In Visual Studio
- How To Monitor Azure Functions
- How To Store Logs in Azure Functions Which Can Be Accessed Later
I am Rajkishore, and I am a Microsoft Certified IT Consultant. I have over 14 years of experience in Microsoft Azure and AWS, with good experience in Azure Functions, Storage, Virtual Machines, Logic Apps, PowerShell Commands, CLI Commands, Machine Learning, AI, Azure Cognitive Services, DevOps, etc. Not only that, I do have good real-time experience in designing and developing cloud-native data integrations on Azure or AWS, etc. I hope you will learn from these practical Azure tutorials. Read more.
