Getting an error of Existing Resource while using function ARM template

Question

I am wrting a Function ARM template for CI/CD the function is already hosted on the Azure portal Now I decided to create an ARM function template and am getting the below error. It saying I cannot create a resource which already exists. I know the resource already exists but I want to create a CI/CD pipline based on the template. I have tried the incremental mode but it seems I am missing something. Is there any guidance online? I have taken the Azure Function Template from the AZURE Git.

C:\Program Files\Microsoft SDKs\Azure.NET SDK\v2.9> az group deployment validate --mode Incremental --resource-group cloud-shell-storage-southeastasia --template-file azuredeploy.json

Please provide string value for 'appName' (? for help): SchedulerHttpFunctionSample

azuredeploy.json
{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "appName": {
      "type": "string",
      "metadata": {
        "description": "The name of the function app that you wish to create."
      }
    },
    "storageAccountType": {
      "type": "string",
      "defaultValue": "Standard_LRS",
      "allowedValues": [
        "Standard_LRS",
        "Standard_GRS",
        "Standard_RAGRS"
      ],
      "metadata": {
        "description": "Storage Account type"
      }
    },
    "location": {
      "type": "string",
      "defaultValue": "[resourceGroup().location]",
      "metadata": {
        "description": "Location for all resources."
      }
    },
    "runtime": {
      "type": "string",
      "defaultValue": "node",
      "allowedValues": [
        "node",
        "dotnet",
        "java"
      ],
      "metadata": {
        "description": "The language worker runtime to load in the function app."
      }
    }
  },
  "variables": {
    "functionAppName": "[parameters('appName')]",
    "hostingPlanName": "[parameters('appName')]",
    "applicationInsightsName": "[parameters('appName')]",
    "storageAccountName": "[concat(uniquestring(resourceGroup().id), 'azfunctions')]",
    "storageAccountid": "[concat(resourceGroup().id,'/providers/','Microsoft.Storage/storageAccounts/', variables('storageAccountName'))]",
    "functionWorkerRuntime": "[parameters('runtime')]"
  },
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "name": "[variables('storageAccountName')]",
      "apiVersion": "2018-12-01",
      "location": "[parameters('location')]",
      "kind": "Storage",
      "sku": {
        "name": "[parameters('storageAccountType')]"
      },
      "properties":{
        "mode":"Incremental"
      }
    },
    {
      "type": "Microsoft.Web/serverfarms",
      "apiVersion": "2018-02-01",
      "name": "[variables('hostingPlanName')]",
      "location": "[parameters('location')]",
      "sku": {
        "name": "Y1",
        "tier": "Dynamic"
      },
      "properties": {
        "mode":"Incremental",
        "name": "[variables('hostingPlanName')]",
        "computeMode": "Dynamic"
      }
    },
    {
      "apiVersion": "2018-02-01",
      "type": "Microsoft.Web/sites",
      "name": "[variables('functionAppName')]",
      "location": "[parameters('location')]",
      "kind": "functionapp",
      "dependsOn": [
        "[resourceId('Microsoft.Web/serverfarms', variables('hostingPlanName'))]",
        "[resourceId('Microsoft.Storage/storageAccounts', variables('storageAccountName'))]"
      ],
      "properties": {
        "serverFarmId": "[resourceId('Microsoft.Web/serverfarms', variables('hostingPlanName'))]",
        "mode":"Incremental",
        "siteConfig": {
          "appSettings": [
            {
              "name": "AzureWebJobsStorage",
              "value": "[concat('DefaultEndpointsProtocol=https;AccountName=', variables('storageAccountName'), ';AccountKey=', listKeys(variables('storageAccountid'),'2015-05-01-preview').key1)]"
            },
            {
              "name": "WEBSITE_CONTENTAZUREFILECONNECTIONSTRING",
              "value": "[concat('DefaultEndpointsProtocol=https;AccountName=', variables('storageAccountName'), ';AccountKey=', listKeys(variables('storageAccountid'),'2015-05-01-preview').key1)]"
            },
            {
              "name": "WEBSITE_CONTENTSHARE",
              "value": "[toLower(variables('functionAppName'))]"
            },
            {
              "name": "FUNCTIONS_EXTENSION_VERSION",
              "value": "~2"
            },
            {
              "name": "WEBSITE_NODE_DEFAULT_VERSION",
              "value": "~10"
            },
            {
              "name": "APPINSIGHTS_INSTRUMENTATIONKEY",
              "value": "[reference(resourceId('microsoft.insights/components/', variables('applicationInsightsName')), '2015-05-01').InstrumentationKey]"
            },
            {
              "name": "FUNCTIONS_WORKER_RUNTIME",
              "value": "[variables('functionWorkerRuntime')]"
            }
          ]
        }
      }
    },
    {
      "apiVersion": "2018-02-01",
      "name": "[variables('applicationInsightsName')]",
      "type": "microsoft.insights/components",
      "location": "East US",
      "tags": {
        "[concat('hidden-link:', resourceGroup().id, '/providers/Microsoft.Web/sites/', variables('applicationInsightsName'))]": "Resource"
      },
      "properties": {
        "ApplicationId": "[variables('applicationInsightsName')]",
        "Request_Source": "IbizaWebAppExtensionCreate",
        "mode":"Incremental"
      }
    }
  ]
}

Azure Error: InvalidResourceLocation Message: The resource 'SchedulerHttpFunctionSample' already exists in location 'southcentralus' in resource group 'cloud-shell-storage-southeastasia'. A resource with the same name cannot be created in location 'southeastasia'. Please select a new resource name.

Answer 1

It's because that name is already taken. Function App name need to be globally unique.

I would suggest using a suffix. In the variables section create some variables:

"variables": {
    "suffix": "[uniqueString(resourceGroup().id, resourceGroup().location)]",
    "functionAppName": "[concat(parameters('appName'), variables('suffix'))]"
}

The function uniqueString will generate a unique string base on the information received. So if you redeploy in the same resource group and region the suffix will be the same.

Have a look to this post: http://www.frankysnotes.com/2019/05/how-to-make-your-deployment-successful.html or this video https://www.youtube.com/watch?v=dnb-f4C052w