Azure Functions ARM Template deploy deletes Functions

Question

I've got an ARM template (included below) to deploy an Azure Function App. I deploy it with:

az group deployment create --resource-group my-group --template-file my-function-app.json

This works and I can then deploy my functions successfully using the VS Code plugin or Azure Functions Core Tools.

However, if I then re-deploy the ARM template (for example to update an application setting) then I lose my functions and need to re-deploy them again. Is this expected behaviour? It's not what I observe when deploying e.g. a Web App via an ARM template. Is there something specific I can do when deploying an ARM template for a Function App to preserve my deployed functions?

my-function-app.json:

{
    "$schema": "http://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {
        ...
    },
    "variables": {
        ...
    },
    "resources": [
        {
            "apiVersion": "2015-08-01",
            "type": "Microsoft.Web/sites",
            "name": "[variables('collectorFunctionAppName')]",
            "location": "[parameters('location')]",
            "kind": "functionapp",
            "properties": {
                "serverFarmId": "[resourceId('Microsoft.Web/serverfarms', variables('hostingPlanName'))]",
                "siteConfig": {
                    "appSettings": [
                        {
                            ...
                        }
                    ]
                }
            }
        }
    ],
    "outputs": {}
}

Answer 1

Are you deploying your function as a package? If so, make sure you set this setting in your template, since it will be removed when you redeploy otherwise:

{ "name": "WEBSITE_RUN_FROM_PACKAGE", "value": "1" }