Add support to enable automatic scaling for App Service Environment

src/Aspire.Hosting.Azure.AppService/AzureAppServiceEnvironmentExtensions.cs

@@ -97,8 +97,12 @@ public static IResourceBuilder<AzureAppServiceEnvironmentResource> AddAzureAppSe
                 },
                 Kind = "Linux",
                 IsReserved = true,
-                // Enable per-site scaling so each app service can scale independently
-                IsPerSiteScaling = true
+                // Enable perSiteScaling or automatic scaling so each app service can scale independently
+                // Default is automatic scaling where Scaling is managed by platform based on HTTP traffic patterns
+                IsPerSiteScaling = !resource.EnableAutomaticScaling,
+                IsElasticScaleEnabled = resource.EnableAutomaticScaling,
+                // Capping the automatic scaling limit to 10 as per best practices
+                MaximumElasticWorkerCount = 10
             };
 
             infra.Add(plan);
@@ -170,4 +174,16 @@ public static IResourceBuilder<AzureAppServiceEnvironmentResource> WithDashboard
         builder.Resource.EnableDashboard = enable;
         return builder;
     }
+
+    /// <summary>
+    /// Configures whether automatic scaling should be enabled for the app services in Azure App Service environment.
+    /// </summary>
+    /// <param name="builder">The AzureAppServiceEnvironmentResource to configure.</param>
+    /// <param name="enable">Whether to enable automatic scaling. Default is true.</param>
+    /// <returns><see cref="IResourceBuilder{T}"/></returns>
+    public static IResourceBuilder<AzureAppServiceEnvironmentResource> WithAutomaticScaling(this IResourceBuilder<AzureAppServiceEnvironmentResource> builder, bool enable = true)
+    {
+        builder.Resource.EnableAutomaticScaling = enable;
+        return builder;
+    }
 }

src/Aspire.Hosting.Azure.AppService/AzureAppServiceEnvironmentResource.cs

@@ -42,6 +42,12 @@ public class AzureAppServiceEnvironmentResource(string name, Action<AzureResourc
     /// </summary>
     internal bool EnableDashboard { get; set; } = true;
 
+    /// <summary>
+    /// Enables or disables automatic scaling for the App Service Plan.
+    /// Default is true.
+    /// </summary>
+    internal bool EnableAutomaticScaling { get; set; } = true;
+
     /// <summary>
     /// Gets the name of the App Service Plan.
     /// </summary>

src/Aspire.Hosting.Azure.AppService/AzureAppServiceEnvironmentUtility.cs

@@ -64,8 +64,10 @@ public static WebSite AddDashboard(AzureResourceInfrastructure infra,
                 UseManagedIdentityCreds = true,
                 IsHttp20Enabled = true,
                 Http20ProxyFlag = 1,
-                // Setting NumberOfWorkers to 1 to ensure dashboard runs on 1 instance
+                // Setting instance count to 1 to ensure dashboard runs on 1 instance
                 NumberOfWorkers = 1,
+                FunctionAppScaleLimit = 1,
+                ElasticWebAppScaleLimit = 1,
                 // IsAlwaysOn set to true ensures the app is always running
                 IsAlwaysOn = true,
                 AppSettings = []

tests/Aspire.Hosting.Azure.Tests/AzureAppServiceTests.cs

@@ -453,6 +453,27 @@ await Verify(manifest.ToString(), "json")
               .AppendContentAsFile(bicep, "bicep");
     }
 
+    [Fact]
+    public async Task AddAppServiceToEnvironmentWithoutAutoScale()
+    {
+        var builder = TestDistributedApplicationBuilder.Create(DistributedApplicationOperation.Publish);
+
+        builder.AddAzureAppServiceEnvironment("env").WithAutomaticScaling(false);
+
+        using var app = builder.Build();
+
+        await ExecuteBeforeStartHooksAsync(app, default);
+
+        var model = app.Services.GetRequiredService<DistributedApplicationModel>();
+
+        var environment = Assert.Single(model.Resources.OfType<AzureAppServiceEnvironmentResource>());
+
+        var (manifest, bicep) = await GetManifestWithBicep(environment);
+
+        await Verify(manifest.ToString(), "json")
+              .AppendContentAsFile(bicep, "bicep");
+    }
+
     [Fact]
     public async Task AddAppServiceWithArgs()
     {

tests/Aspire.Hosting.Azure.Tests/Snapshots/AzureAppServiceTests.AddAppServiceEnvironmentWithoutDashboardAddsEnvironmentResource.verified.bicep

@@ -34,8 +34,10 @@ resource env_asplan 'Microsoft.Web/serverfarms@2024-11-01' = {
   name: take('envasplan-${uniqueString(resourceGroup().id)}', 60)
   location: location
   properties: {
-    perSiteScaling: true
+    elasticScaleEnabled: true
+    perSiteScaling: false
     reserved: true
+    maximumElasticWorkerCount: 10
   }
   kind: 'Linux'
   sku: {

tests/Aspire.Hosting.Azure.Tests/Snapshots/AzureAppServiceTests.AddAppServiceToEnvironmentWithoutAutoScale.verified.bicep

@@ -0,0 +1,149 @@
+@description('The location for the resource(s) to be deployed.')
+param location string = resourceGroup().location
+
+param userPrincipalId string = ''
+
+param tags object = { }
+
+resource env_mi 'Microsoft.ManagedIdentity/userAssignedIdentities@2024-11-30' = {
+  name: take('env_mi-${uniqueString(resourceGroup().id)}', 128)
+  location: location
+  tags: tags
+}
+
+resource env_acr 'Microsoft.ContainerRegistry/registries@2025-04-01' = {
+  name: take('envacr${uniqueString(resourceGroup().id)}', 50)
+  location: location
+  sku: {
+    name: 'Basic'
+  }
+  tags: tags
+}
+
+resource env_acr_env_mi_AcrPull 'Microsoft.Authorization/roleAssignments@2022-04-01' = {
+  name: guid(env_acr.id, env_mi.id, subscriptionResourceId('Microsoft.Authorization/roleDefinitions', '7f951dda-4ed3-4680-a7ca-43fe172d538d'))
+  properties: {
+    principalId: env_mi.properties.principalId
+    roleDefinitionId: subscriptionResourceId('Microsoft.Authorization/roleDefinitions', '7f951dda-4ed3-4680-a7ca-43fe172d538d')
+    principalType: 'ServicePrincipal'
+  }
+  scope: env_acr
+}
+
+resource env_asplan 'Microsoft.Web/serverfarms@2024-11-01' = {
+  name: take('envasplan-${uniqueString(resourceGroup().id)}', 60)
+  location: location
+  properties: {
+    elasticScaleEnabled: false
+    perSiteScaling: true
+    reserved: true
+    maximumElasticWorkerCount: 10
+  }
+  kind: 'Linux'
+  sku: {
+    name: 'P0V3'
+    tier: 'Premium'
+  }
+}
+
+resource env_contributor_mi 'Microsoft.ManagedIdentity/userAssignedIdentities@2024-11-30' = {
+  name: take('env_contributor_mi-${uniqueString(resourceGroup().id)}', 128)
+  location: location
+}
+
+resource env_ra 'Microsoft.Authorization/roleAssignments@2022-04-01' = {
+  name: guid(resourceGroup().id, env_contributor_mi.id, subscriptionResourceId('Microsoft.Authorization/roleDefinitions', 'acdd72a7-3385-48ef-bd42-f606fba81ae7'))
+  properties: {
+    principalId: env_contributor_mi.properties.principalId
+    roleDefinitionId: subscriptionResourceId('Microsoft.Authorization/roleDefinitions', 'acdd72a7-3385-48ef-bd42-f606fba81ae7')
+    principalType: 'ServicePrincipal'
+  }
+}
+
+resource dashboard 'Microsoft.Web/sites@2024-11-01' = {
+  name: take('${toLower('env')}-${toLower('aspiredashboard')}-${uniqueString(resourceGroup().id)}', 60)
+  location: location
+  properties: {
+    serverFarmId: env_asplan.id
+    siteConfig: {
+      numberOfWorkers: 1
+      linuxFxVersion: 'ASPIREDASHBOARD|1.0'
+      acrUseManagedIdentityCreds: true
+      acrUserManagedIdentityID: env_mi.properties.clientId
+      appSettings: [
+        {
+          name: 'Dashboard__Frontend__AuthMode'
+          value: 'Unsecured'
+        }
+        {
+          name: 'Dashboard__Otlp__AuthMode'
+          value: 'Unsecured'
+        }
+        {
+          name: 'Dashboard__Otlp__SuppressUnsecuredTelemetryMessage'
+          value: 'true'
+        }
+        {
+          name: 'Dashboard__ResourceServiceClient__AuthMode'
+          value: 'Unsecured'
+        }
+        {
+          name: 'WEBSITES_PORT'
+          value: '5000'
+        }
+        {
+          name: 'HTTP20_ONLY_PORT'
+          value: '4317'
+        }
+        {
+          name: 'WEBSITE_START_SCM_WITH_PRELOAD'
+          value: 'true'
+        }
+        {
+          name: 'AZURE_CLIENT_ID'
+          value: env_contributor_mi.properties.clientId
+        }
+        {
+          name: 'ALLOWED_MANAGED_IDENTITIES'
+          value: env_mi.properties.clientId
+        }
+        {
+          name: 'ASPIRE_ENVIRONMENT_NAME'
+          value: 'env'
+        }
+      ]
+      alwaysOn: true
+      http20Enabled: true
+      http20ProxyFlag: 1
+      functionAppScaleLimit: 1
+      elasticWebAppScaleLimit: 1
+    }
+  }
+  identity: {
+    type: 'UserAssigned'
+    userAssignedIdentities: {
+      '${env_contributor_mi.id}': { }
+    }
+  }
+  kind: 'app,linux,aspiredashboard'
+}
+
+output name string = env_asplan.name
+
+output planId string = env_asplan.id
+
+output webSiteSuffix string = uniqueString(resourceGroup().id)
+
+output AZURE_CONTAINER_REGISTRY_NAME string = env_acr.name
+
+output AZURE_CONTAINER_REGISTRY_ENDPOINT string = env_acr.properties.loginServer
+
+output AZURE_CONTAINER_REGISTRY_MANAGED_IDENTITY_ID string = env_mi.id
+
+output AZURE_CONTAINER_REGISTRY_MANAGED_IDENTITY_CLIENT_ID string = env_mi.properties.clientId
+
+output AZURE_WEBSITE_CONTRIBUTOR_MANAGED_IDENTITY_ID string = env_contributor_mi.id
+
+output AZURE_WEBSITE_CONTRIBUTOR_MANAGED_IDENTITY_PRINCIPAL_ID string = env_contributor_mi.properties.principalId
+
+output AZURE_APP_SERVICE_DASHBOARD_URI string = 'https://${take('${toLower('env')}-${toLower('aspiredashboard')}-${uniqueString(resourceGroup().id)}', 60)}.azurewebsites.net'

tests/Aspire.Hosting.Azure.Tests/Snapshots/AzureAppServiceTests.AddAppServiceToEnvironmentWithoutAutoScale.verified.json

@@ -0,0 +1,7 @@
+{
+  "type": "azure.bicep.v0",
+  "path": "env.module.bicep",
+  "params": {
+    "userPrincipalId": ""
+  }
+}

tests/Aspire.Hosting.Azure.Tests/Snapshots/AzureAppServiceTests.AddContainerAppEnvironmentAddsEnvironmentResource.verified.bicep

@@ -34,8 +34,10 @@ resource env_asplan 'Microsoft.Web/serverfarms@2024-11-01' = {
   name: take('envasplan-${uniqueString(resourceGroup().id)}', 60)
   location: location
   properties: {
-    perSiteScaling: true
+    elasticScaleEnabled: true
+    perSiteScaling: false
     reserved: true
+    maximumElasticWorkerCount: 10
   }
   kind: 'Linux'
   sku: {
@@ -113,6 +115,8 @@ resource dashboard 'Microsoft.Web/sites@2024-11-01' = {
       alwaysOn: true
       http20Enabled: true
       http20ProxyFlag: 1
+      functionAppScaleLimit: 1
+      elasticWebAppScaleLimit: 1
     }
   }
   identity: {
@@ -142,4 +146,4 @@ output AZURE_WEBSITE_CONTRIBUTOR_MANAGED_IDENTITY_ID string = env_contributor_mi
 
 output AZURE_WEBSITE_CONTRIBUTOR_MANAGED_IDENTITY_PRINCIPAL_ID string = env_contributor_mi.properties.principalId
 
-output AZURE_APP_SERVICE_DASHBOARD_URI string = 'https://${take('${toLower('env')}-${toLower('aspiredashboard')}-${uniqueString(resourceGroup().id)}', 60)}.azurewebsites.net'
+output AZURE_APP_SERVICE_DASHBOARD_URI string = 'https://${take('${toLower('env')}-${toLower('aspiredashboard')}-${uniqueString(resourceGroup().id)}', 60)}.azurewebsites.net'

tests/Aspire.Hosting.Azure.Tests/Snapshots/AzureAppServiceTests.AzureAppServiceEnvironmentCanReferenceExistingAppServicePlan.verified.bicep

@@ -34,8 +34,10 @@ resource env_asplan 'Microsoft.Web/serverfarms@2024-11-01' = {
   name: take('envasplan-${uniqueString(resourceGroup().id)}', 60)
   location: location
   properties: {
-    perSiteScaling: true
+    elasticScaleEnabled: true
+    perSiteScaling: false
     reserved: true
+    maximumElasticWorkerCount: 10
   }
   kind: 'Linux'
   sku: {
@@ -113,6 +115,8 @@ resource dashboard 'Microsoft.Web/sites@2024-11-01' = {
       alwaysOn: true
       http20Enabled: true
       http20ProxyFlag: 1
+      functionAppScaleLimit: 1
+      elasticWebAppScaleLimit: 1
     }
   }
   identity: {
@@ -142,4 +146,4 @@ output AZURE_WEBSITE_CONTRIBUTOR_MANAGED_IDENTITY_ID string = env_contributor_mi
 
 output AZURE_WEBSITE_CONTRIBUTOR_MANAGED_IDENTITY_PRINCIPAL_ID string = env_contributor_mi.properties.principalId
 
-output AZURE_APP_SERVICE_DASHBOARD_URI string = 'https://${take('${toLower('env')}-${toLower('aspiredashboard')}-${uniqueString(resourceGroup().id)}', 60)}.azurewebsites.net'
+output AZURE_APP_SERVICE_DASHBOARD_URI string = 'https://${take('${toLower('env')}-${toLower('aspiredashboard')}-${uniqueString(resourceGroup().id)}', 60)}.azurewebsites.net'