# Upgrading a Functions App and Code-base to the v4 Runtime
References.

- [Migrate apps from Azure Functions version 3.x to version 4.x](https://learn.microsoft.com/en-us/azure/azure-functions/migrate-version-3-version-4?tabs=net6-in-proc%2Cazure-cli%2Cwindows&pivots=programming-language-javascript)
- [Azure Functions runtime versions overview](https://learn.microsoft.com/en-us/azure/azure-functions/functions-versions?tabs=v4&pivots=programming-language-javascript#migrating-from-3x-to-4x)
- [Work with Azure Functions Core Tools](https://learn.microsoft.com/en-us/azure/azure-functions/functions-run-local?tabs=v4%2Cmacos%2Ccsharp%2Cportal%2Cbash#install-the-azure-functions-core-tools)
- [Durable Functions versions overview](https://learn.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-versions)
- [Extension bundles](https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-register#extension-bundles)
- [Fix output data serialization format in Node.js functions #2007](https://github.com/Azure/Azure-Functions/issues/2007)

> _Version 3.x of the extension bundle doesn't include the Table Storage bindings, if you require the Table Storage binding, you should continue using the 2.x version._

## Actions
- Run the **```Functions 4.x Pre-Upgrade Validator```** in _Azure ➜ Functions App ➜ Diagnose and Solve Problems_
- ➜ Remove **AzureWebJobsDashboard** app setting

	_this is a legacy setting that may have been added when creating older function apps_

- ➜ Remove **APPINSIGHTS_INSTRUMENTATIONKEY** app setting

   _this gets added by default when you enable Application Insights using the Azure Portal_

- ➜ Upgrade local **Azure Functions Core Tools** to **v4**
```
# I'm using homebrew, otherwise you should pick your package manager of choice
# but the same one you originally installed any previous version of the core tools with!!!

brew tap azure/functions
brew install azure-functions-core-tools@4

# if upgrading on a machine that has 2.x or 3.x installed:
brew link --overwrite azure-functions-core-tools@4
```
- Set NVM default Node to **`v16`**
```
nvm alias default 16.17.0
```

- Set **`hubName`** in **`host.json`** to **`<preferred hub name>`** or _`durablefunctionshub` (this is the default if not supplied)_
```
{
	"extensions": {
		"durableTask": {
			"hubName": "<preferred hub name>",
		}
	}
}
```
- Upgrade the **extension bundle** to **v2**

Set **`extensionBundle`** to **2.\*, 3.0.0** in **`host.json`**

_This is a minimum requirement for the functions v4 runtime and is also a requirement to use **durable entities** with durable functions v2.0, so the extension upgrade is a win-win_
```
{
   "extensionBundle": {
      "id": "Microsoft.Azure.Functions.ExtensionBundle",
      "version": "[2.*, 3.0.0)"
   }
}

```
- Change the durable client function binding type from **```orchestrationClient```** to **```durableClient```** in **all** `function.json` files
- Change **FUNCTIONS_EXTENSION_VERSION** to **~4** in `local.settings.json`
- Update _Dev/Debug_ webpack build process to also copy the non-functional **`package.json`** file from the **`src`** folder to the **`dist`** folder


## Upgrade the Azure Functions App to use the v4 runtime
- Set the functions app **runtime version** to **v4**

See:  [az functionapp config appsettings set](https://learn.microsoft.com/en-us/cli/azure/functionapp/config/appsettings?view=azure-cli-latest#az-functionapp-config-appsettings-set)
```
az functionapp config appsettings set --settings "FUNCTIONS_EXTENSION_VERSION=~4" --resource-group <resource group> --name <functions app name>
```
- Set the functions app **node version** to **16**
```
az functionapp config appsettings set --settings "WEBSITE_NODE_DEFAULT_VERSION=~16" --resource-group <resource group> --name <functions app name>
```
- Set the functions app **.NET version** to **v6.0** -- _only for OS type=Windows*_

See:  [az functionapp config set](https://learn.microsoft.com/en-us/cli/azure/functionapp/config?view=azure-cli-latest#az-functionapp-config-set)

_The default for the v3 runtime is ```"netFrameworkVersion": "v4.0"```_
```
az functionapp config show --resource-group <resource group> --name <functions app name>
az functionapp config set --net-framework-version v6.0 --resource-group <resource group> --name <functions app name>
```
- **Restart** the functions app

See:  [az functionapp restart](https://learn.microsoft.com/en-us/cli/azure/functionapp?view=azure-cli-latest#az-functionapp-restart)
```
az functionapp restart --resource-group <resource group> --name <functions app name>
```
---
> If you visit the functions app in the Azure Portal now you will see the following error in the **Overview** blade.
> This is because the extension bundle of the currently deployed project code-base does not meet minimum version requirements for the **v4** runtime.
>
> _Microsoft.Azure.WebJobs.Script: Referenced bundle Microsoft.Azure.Functions.ExtensionBundle of version 1.8.1 does not meet the required minimum version of 2.6.1_
> _Update your extension bundle reference in host.json to reference 2.6.1 or later_
>
> For more information see https://aka.ms/func-min-bundle-versions.
>
> 
> **Redeploy your updated codebase.**
> 
> 
> **```** If the error persists *****************************************```**
>
> see this article: https://stackoverflow.com/questions/75991406/how-do-you-solve-azfd0005-azure-function-app-error
>
> **```******************************************************************```**
>

---

- **Remove** the **node_modules** folder and **re-install package dependencies**

_Ensure you've upgraded your Node version to 16, 14 etc_

```
rm node_modules
 or
del node_modules

npm install
```

- **Build and deploy** the updated project code-base