How to use a DocumentDB(MongoDB) connection string as an Environment variable in an Azure Resource Management Template

Question

I want to use a DocumentDB(MongoDB) connection string as an environment variable in an Azure Resource Management Template. Forexample i have a resource group which has a wep app and a DocumentDB(MongoDB) database.

"siteConfig": {
          "appSettings": [
            {
              "name": "db",
              "value": "connection string"
            }
          ]
        }

How can i assign an environment variable to a connection string in template?

Answer 1

ARM template supports listKeys and list{Value} function, more details we can refer to ARM template function. We can find DocumentDB list connection strings API, so we can use listconnectionstrings function to get documentdb connection string in the ARM template.

"appSettings": [
            {
              "name": "db",
              "value": " [listConnectionStrings(resourceId('Microsoft.DocumentDb/databaseAccounts', parameters('documentdb')), '2015-04-08').connectionStrings[0].connectionString]"
            }

It works correct on my side. If we want to add appsetting for WebApp, we also can do with following code

  "resources": [
      {
          "name": "appsettings",
          "type": "config",
          "apiVersion": "2015-08-01",
          "dependsOn": [
              "[resourceId('Microsoft.Web/sites', variables('webSiteName'))]"
          ],
          "tags": {
              "displayName": "appsetting"
          },
        "properties": {
          "db": "[listConnectionStrings(resourceId('Microsoft.DocumentDb/databaseAccounts', parameters('documentdb')), '2015-04-08').connectionStrings[0].connectionString]"
        }
      }

  ]

Check the result from the Azure portal.

Update:

ARM template demo code

{
  "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "hostingPlanName": {
      "type": "string",
      "minLength": 1
    },
    "documentdb": {
      "type": "string",
      "minLength": 1
    },
    "skuName": {
      "type": "string",
      "defaultValue": "S1",
      "allowedValues": [
        "F1",
        "D1",
        "B1",
        "B2",
        "B3",
        "S1",
        "S2",
        "S3",
        "P1",
        "P2",
        "P3",
        "P4"
      ],
      "metadata": {
        "description": "Describes plan's pricing tier and instance size. Check details at https://azure.microsoft.com/en-us/pricing/details/app-service/"
      }
    },
    "skuCapacity": {
      "type": "int",
      "defaultValue": 1,
      "minValue": 1,
      "metadata": {
        "description": "Describes plan's instance count"
      }
    }
  },
  "variables": {
    "webSiteName": "[concat('webSite', uniqueString(resourceGroup().id))]",
    "docDbName": "tomdocumentdb",
    "storageAccountId": "[concat(resourceGroup().id,'/providers/Microsoft.Storage/storageAccounts/', parameters('storageAccountName'))]"
  },
  "resources": [
    {
      "apiVersion": "2015-08-01",
      "name": "[parameters('hostingPlanName')]",
      "type": "Microsoft.Web/serverfarms",
      "location": "[resourceGroup().location]",
      "tags": {
        "displayName": "HostingPlan"
      },
      "sku": {
        "name": "[parameters('skuName')]",
        "capacity": "[parameters('skuCapacity')]"
      },
      "properties": {
        "name": "[parameters('hostingPlanName')]"
      }
    },
    {
      "apiVersion": "2015-08-01",
      "name": "[variables('webSiteName')]",
      "type": "Microsoft.Web/sites",
      "location": "[resourceGroup().location]",
      "tags": {
        "[concat('hidden-related:', resourceGroup().id, '/providers/Microsoft.Web/serverfarms/', parameters('hostingPlanName'))]": "Resource",
        "displayName": "Website"
      },
      "dependsOn": [
        "[concat('Microsoft.Web/serverfarms/', parameters('hostingPlanName'))]"
      ],
      "properties": {
        "name": "[variables('webSiteName')]",
        "serverFarmId": "[resourceId('Microsoft.Web/serverfarms', parameters('hostingPlanName'))]"
      },

      "resources": [
          {
              "name": "appsettings",
              "type": "config",
              "apiVersion": "2015-08-01",
              "dependsOn": [
                  "[resourceId('Microsoft.Web/sites', variables('webSiteName'))]"
              ],
              "tags": {
                  "displayName": "appsetting"
              },
            "properties": {
              "db": "[listConnectionStrings(resourceId('Microsoft.DocumentDb/databaseAccounts', parameters('documentdb')), '2015-04-08').connectionStrings[0].connectionString]"
            }
          }

      ]
    }
  ]
}

Paramter file

{
    "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentParameters.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {
        "hostingPlanName": {
            "value": "tomtest" //your hostingplan name
        },
        "skuName": {
            "value": "B1"
        },
        "documentdb": {
            "value": "tomdocument" // your documentdb name
        }

    }
}