Exercise - Refactor your Bicep file to use modules

In this exercise, you'll update the Bicep file you previously created so it uses a module for the Azure App Service resources. Modules help to keep the intention of the main file clearer. You can reuse the App Service module in other Bicep files if you choose to.

During the process, you'll:

Add a new module file

Create a self-contained module for your App Service resources:

1. In Visual Studio Code, create a new folder called modules in the same folder where you created your main.bicep file. In the modules folder, create a file called appService.bicep. Save the file.

2. Add the following content into the appService.bicep file:

   param location string
   param appServiceAppName string
   
   @allowed([
     'nonprod'
     'prod'
   ])
   param environmentType string
   
   var appServicePlanName = 'toy-product-launch-plan'
   var appServicePlanSkuName = (environmentType == 'prod') ? 'P2v3' : 'F1'
   
   resource appServicePlan 'Microsoft.Web/serverfarms@2024-04-01' = {
     name: appServicePlanName
     location: location
     sku: {
       name: appServicePlanSkuName
     }
   }
   
   resource appServiceApp 'Microsoft.Web/sites@2024-04-01' = {
     name: appServiceAppName
     location: location
     properties: {
       serverFarmId: appServicePlan.id
       httpsOnly: true
     }
   }
   

   Notice that you've copied the parameters and variables from your main.bicep Bicep file since the appService.bicep Bicep file needs to be self-contained.

3. Save the changes to the file. Notice that Visual Studio Code doesn't show you any red squiggles to indicate warnings about missing variables, missing parameters, or invalid resources.

Add a reference to the module from the parent Bicep file

Now that you've created a complete module to deploy the App Service resources, you can refer to the module within the parent Bicep file. Because the module deploys the App Service resources, you can delete the associated resources and variables from the parent file.

1. In the main.bicep file, delete the App Service resources and the appServicePlanName and appServicePlanSkuName variable definitions. Don't delete the App Service parameters, because you still need them. Also, don't delete the storage account parameters, variable, or resources.

2. At the bottom of the main.bicep file, add the following Bicep code:

   module appService 'modules/appService.bicep' = {
     name: 'appService'
     params: {
       location: location
       appServiceAppName: appServiceAppName
       environmentType: environmentType
     }
   }
   

   Notice that you're specifying the parameters for your module by referencing the parameters in the parent Bicep file.

3. Save the changes to the file.

Add the host name as an output

Expose the app's host name from both the module and its parent file:

1. Add the following Bicep code at the bottom of the appService.bicep file:

   output appServiceAppHostName string = appServiceApp.properties.defaultHostName
   

   This code declares that an output for this module, which will be named appServiceAppHostName, will be of type string. The output will take its value from the defaultHostName property of the App Service app.

2. Save the changes to the file.

   The output is declared in the App Service module. The parent file can read it through appService.outputs.appServiceAppHostName, but it isn't automatically included in the parent deployment's outputs. Add a matching output to the parent file so that someone inspecting the main deployment can retrieve it there. This ordinary, non-secret output can also be read from the module's nested deployment record by a user with the required deployment read permissions.

3. Open the main.bicep file and add the following code at the bottom of the file:

   output appServiceAppHostName string = appService.outputs.appServiceAppHostName
   

   Notice that this output is declared in a similar way to the output in the module. But this time, you're referencing the module's output instead of a resource property.

4. Save the changes to the file.

Verify your Bicep files

After you've completed all of the preceding changes, your main.bicep file should look like this example:

param location string = 'eastus'
param storageAccountName string = 'toylaunch${uniqueString(resourceGroup().id)}'
param appServiceAppName string = 'toylaunch${uniqueString(resourceGroup().id)}'

@allowed([
  'nonprod'
  'prod'
])
param environmentType string

var storageAccountSkuName = (environmentType == 'prod') ? 'Standard_GRS' : 'Standard_LRS'

resource storageAccount 'Microsoft.Storage/storageAccounts@2023-05-01' = {
  name: storageAccountName
  location: location
  sku: {
    name: storageAccountSkuName
  }
  kind: 'StorageV2'
  properties: {
    accessTier: 'Hot'
  }
}

module appService 'modules/appService.bicep' = {
  name: 'appService'
  params: {
    location: location
    appServiceAppName: appServiceAppName
    environmentType: environmentType
  }
}

output appServiceAppHostName string = appService.outputs.appServiceAppHostName

Your appService.bicep file should look like this example:

param location string
param appServiceAppName string

@allowed([
  'nonprod'
  'prod'
])
param environmentType string

var appServicePlanName = 'toy-product-launch-plan'
var appServicePlanSkuName = (environmentType == 'prod') ? 'P2v3' : 'F1'

resource appServicePlan 'Microsoft.Web/serverfarms@2024-04-01' = {
  name: appServicePlanName
  location: location
  sku: {
    name: appServicePlanSkuName
  }
}

resource appServiceApp 'Microsoft.Web/sites@2024-04-01' = {
  name: appServiceAppName
  location: location
  properties: {
    serverFarmId: appServicePlan.id
    httpsOnly: true
  }
}

output appServiceAppHostName string = appServiceApp.properties.defaultHostName

If either Bicep file doesn't match, copy the example or adjust your file to match the example.

Deploy the updated Bicep file

az deployment group create \
  --resource-group "$resourceGroupName" \
  --name main \
  --template-file main.bicep \
  --parameters environmentType=nonprod

New-AzResourceGroupDeployment `
  -ResourceGroupName $resourceGroupName `
  -Name main `
  -TemplateFile main.bicep `
  -environmentType nonprod

Check your deployment

Confirm that the module deployed and returned the app's host name:

1. In your browser, return to the Azure portal. Go to your resource group and open Deployments.

2. Locate the main deployment and the nested appService deployment. A successful run creates or updates these named entries. Other deployments might also be listed.

   

3. Select the deployment called main. Confirm that its latest operation succeeded and corresponds to the command you just ran, then select Deployment details to expand the list of deployed resources.

   Notice that our module deployment appears in the list.

   

4. Select the Outputs tab. Notice that there's an output called appServiceAppHostName with the host name of your App Service app. Copy the host name to your clipboard.

   

5. Open a new browser tab and paste the host name that you copied. You should see the default App Service welcome page.

   

Congratulations! You've successfully deployed the foundations for a great app.