Monitor Azure app services performance


Enabling monitoring on your .NET and .NET Core based web applications running on Azure App Services is now easier than ever. Whereas previously you needed to manually install a site extension, the latest extension/agent is now built into the app service image by default. This article will walk you through enabling Application Insights monitoring as well as provide preliminary guidance for automating the process for large-scale deployments.


Manually adding an Application Insights site extension via Development Tools > Extensions is deprecated. The latest stable release of the extension is now preinstalled as part of the App Service image. The files are located in d:Program Files (x86)SiteExtensionsApplicationInsightsAgent and are automatically updated with each stable release. If you follow the agent based instructions to enable monitoring below, it will automatically remove the deprecated extension for you.

Enable Application Insights

There are two ways to enable application monitoring for Azure App Services hosted applications:

  • Agent-based application monitoring (ApplicationInsightsAgent).

    • This method is the easiest to enable, and no advanced configuration is required. It is often referred to as “runtime” monitoring. For Azure App Services we recommend at a minimum enabling this level of monitoring, and then based on your specific scenario you can evaluate whether more advanced monitoring through manual instrumentation is needed.
  • Manually instrumenting the application through code by installing the Application Insights SDK.


If both agent based monitoring and manual SDK based instrumentation is detected only the manual instrumentation settings will be honored. This is to prevent duplicate data from sent. To learn more about this check out the troubleshooting section below.

Enable agent-based monitoring .NET

  1. Select Application Insights in the Azure control panel for your app service.

    Under Settings, choose Application Insights

  2. After specifying which resource to use, you can choose how you want application insights to collect data per platform for your application. ASP.NET app monitoring is on-by-default with two different levels of collection.

    Choose options per platform

  3. To configure settings like sampling, which you could previously control via the applicationinsights.config file you can now interact with those same settings via Application settings with a corresponding prefix.

    • For example, to change the initial sampling percentage, you can create an Application setting of: MicrosoftAppInsights_AdaptiveSamplingTelemetryProcessor_InitialSamplingPercentage and a value of 100.

    • For the list of supported adaptive sampling telemetry processor settings, you can consult the code and associated documentation.

Enable agent-based monitoring .NET Core

The following versions of .NET Core are supported: ASP.NET Core 2.0, ASP.NET Core 2.1, ASP.NET Core 2.2

Targeting the full framework from .NET Core, self-contained deployment, and ASP.NET Core 3.0 are currently not supported with agent/extension based monitoring. (Manual instrumentation via code will work in all of the previous scenarios.)

  1. Select Application Insights in the Azure control panel for your app service.

    Under Settings, choose Application Insights

  2. After specifying which resource to use, you can choose how you want Application Insights to collect data per platform for your application. .NET Core offers Recommended collection or Disabled for .NET Core 2.0, 2.1, and 2.2.

    Choose options per platform

Enable client-side monitoring .NET

Client-side monitoring is opt-in for ASP.NET. To enable client-side monitoring:

  • Select Settings >** Application settings**
    • Under Application settings, add a new app setting name and value:


      Value: true

    • Save the settings and Restart your app.

Screenshot of application settings UI

To disable client-side monitoring either remove the associated key value pair from the Application settings, or set the value to false.

Enable client-side monitoring .NET Core

Client-side monitoring is enabled by default for .NET Core apps with Recommended collection, regardless of whether the app setting ‘APPINSIGHTS_JAVASCRIPT_ENABLED’ is present.

If for some reason you would like to disable client-side monitoring:

  • Select Settings > Application settings
    • Under Application settings, add a new app setting name and value:


      Value: false

    • Save the settings and Restart your app.

Screenshot of application settings UI

Automate monitoring

In order to enable telemetry collection with Application Insights, only the Application settings need to be set:

App Service Application Settings with available Application Insights settings

Application settings definitions

App setting name Definition Value
ApplicationInsightsAgent_EXTENSION_VERSION Main extension, which controls runtime monitoring. ~2
XDT_MicrosoftApplicationInsights_Mode In default mode only, essential features are enabled in order to insure optimal performance. default or recommended.
InstrumentationEngine_EXTENSION_VERSION Controls if the binary-rewrite engine InstrumentationEngine will be turned on. This setting has performance implications and impacts cold start/startup time. ~1
XDT_MicrosoftApplicationInsights_BaseExtensions Controls if SQL & Azure table text will be captured along with the dependency calls. Performance warning: this setting requires the InstrumentationEngine. ~1

App Service Application settings with Azure Resource Manager

Application settings for App Services can be managed and configured with Azure Resource Manager templates. This method can be used when deploying new App Service resources with Azure Resource Manager automation, or for modifying the settings of existing resources.

The basic structure of the application settings JSON for an app service is below:

      "resources": [
          "name": "appsettings",
          "type": "config",
          "apiVersion": "2015-08-01",
          "dependsOn": [
            "[resourceId('Microsoft.Web/sites', variables('webSiteName'))]"
            "displayName": "Application Insights Settings"
            "key1": "value1",
            "key2": "value2"

For an example of an Azure Resource Manager template with Application settings configured for Application Insights, this template can be helpful, specifically the section starting on line 238.

To create an Azure Resource Manager template with all the default Application Insights settings configured, begin the process as if you were going to create a new Web App with Application Insights enabled.

Select Automation options

App Service web app creation menu

This option generates the latest Azure Resource Manager template with all required settings configured.

App Service web app template

Below is a sample, replace all instances of AppMonitoredSite with your site name:

    "resources": [
            "name": "[parameters('name')]",
            "type": "Microsoft.Web/sites",
                    "appSettings": [
                            "name": "APPINSIGHTS_INSTRUMENTATIONKEY",
                            "value": "[reference('microsoft.insights/components/AppMonitoredSite', '2015-05-01').InstrumentationKey]"
                            "name": "ApplicationInsightsAgent_EXTENSION_VERSION",
                            "value": "~2"
                "name": "[parameters('name')]",
                "serverFarmId": "[concat('/subscriptions/', parameters('subscriptionId'),'/resourcegroups/', parameters('serverFarmResourceGroup'), '/providers/Microsoft.Web/serverfarms/', parameters('hostingPlanName'))]",
                "hostingEnvironment": "[parameters('hostingEnvironment')]"
            "dependsOn": [
                "[concat('Microsoft.Web/serverfarms/', parameters('hostingPlanName'))]",
            "apiVersion": "2016-03-01",
            "location": "[parameters('location')]"
            "apiVersion": "2016-09-01",
            "name": "[parameters('hostingPlanName')]",
            "type": "Microsoft.Web/serverfarms",
            "location": "[parameters('location')]",
                "name": "[parameters('hostingPlanName')]",
                "workerSizeId": "[parameters('workerSize')]",
                "numberOfWorkers": "1",
                "hostingEnvironment": "[parameters('hostingEnvironment')]"
                "Tier": "[parameters('sku')]",
                "Name": "[parameters('skuCode')]"
            "apiVersion": "2015-05-01",
            "name": "AppMonitoredSite",
            "type": "microsoft.insights/components",
            "location": "West US 2",
                "ApplicationId": "[parameters('name')]",
                "Request_Source": "IbizaWebAppExtensionCreate"
            "type": "string"
            "type": "string"
            "type": "string"
            "type": "string"
            "type": "string"
            "type": "string"
            "type": "string"
            "type": "string"
            "type": "string"
    "$schema": "",
    "contentVersion": ""


The template will generate application settings in “default” mode. This mode is performance optimized, though you can modify the template to activate whichever features you prefer.

Enabling through PowerShell

In order to enable the application monitoring through PowerShell, only the underlying application settings need to be changed. Below is a sample, which enables application monitoring for a website called “AppMonitoredSite” in the resource group “AppMonitoredRG”, and configures data to be sent to the “012345678-abcd-ef01-2345-6789abcd” instrumentation key.

$app = Get-AzureRmWebApp -ResourceGroupName "AppMonitoredRG" -Name "AppMonitoredSite" -ErrorAction Stop
$newAppSettings = @ # case-insensitive hash map
$app.SiteConfig.AppSettings | %$newAppSettings[$_.Name] = $_.Value #preserve non Application Insights Application settings.
$newAppSettings["APPINSIGHTS_INSTRUMENTATIONKEY"] = "012345678-abcd-ef01-2345-6789abcd"; # enable the ApplicationInsightsAgent
$newAppSettings["ApplicationInsightsAgent_EXTENSION_VERSION"] = "~2"; # enable the ApplicationInsightsAgent
$app = Set-AzureRmWebApp -AppSettings $newAppSettings -ResourceGroupName $app.ResourceGroup -Name $app.Name -ErrorAction Stop

Upgrade monitoring extension/agent

Upgrading from versions 2.8.9 and up

Upgrading from version 2.8.9 happens automatically, without any additional actions. The new monitoring bits are delivered in the background to the target app service, and on application restart they will be picked up.

To check which version of the extension you are running visit

Screenshot of url path

Upgrade from versions 1.0.0 – 2.6.5

Starting with version 2.8.9 the pre-installed site extension is used. If you are an earlier version, you can update via one of two ways:

  • Upgrade by enabling via the portal. (Even if you have the Application Insights extension for Azure App Service installed, the UI shows only Enable button. Behind the scenes, the old private site extension will be removed.)

  • Upgrade through PowerShell:

    1. Set the application settings to enable the pre-installed site extension ApplicationInsightsAgent. See Enabling through powershell.
    2. Manually remove the private site extension named Application Insights extension for Azure App Service.

If the upgrade is done from a version prior to 2.5.1, check that the ApplicationInsigths dlls are removed from the application bin folder see troubleshooting steps.


Below is our step-by-step troubleshooting guide for extension/agent based monitoring for .NET and .NET Core based applications running on Azure App Services.


Java and Node.js applications are only supported on Azure App Services via manual SDK based instrumentation and therefore the steps below do not apply to these scenarios.

  1. Check that the application is monitored via ApplicationInsightsAgent.

    • Check that ApplicationInsightsAgent_EXTENSION_VERSION app setting is set to a value of “~2”.
  2. Ensure that the application meets the requirements to be monitored.

    • Browse to

    Screenshot of https://yoursitename.scm.azurewebsites/applicationinsights results page

    • Confirm that the Application Insights Extension Status is Pre-Installed Site Extension, version, is running.

    • Confirm that the status source exists and looks like: Status source D:homeLogFilesApplicationInsightsstatusstatus_RD0003FF0317B6_4248_1.json

      • If a similar value is not present, it means the application is not currently running or is not supported. To ensure that the application is running, try manually visiting the application url/application endpoints, which will allow the runtime information to become available.
    • Confirm that IKeyExists is true

      • If it is false, add `APPINSIGHTS_INSTRUMENTATIONKEY with your ikey guid to your application settings.
    • Confirm that there are no entries for AppAlreadyInstrumented, AppContainsDiagnosticSourceAssembly, and AppContainsAspNetTelemetryCorrelationAssembly.

      • If any of these entries exist, remove the following packages from your application: Microsoft.ApplicationInsights, System.Diagnostics.DiagnosticSource, and Microsoft.AspNet.TelemetryCorrelation.

The table below provides a more detailed explanation of what these values mean, their underlying causes, and recommended fixes:

Problem Value Explanation Fix
AppAlreadyInstrumented:true This value indicates that the extension detected that some aspect of the SDK is already present in the Application, and will back-off. It can be due to a reference to System.Diagnostics.DiagnosticSource, Microsoft.AspNet.TelemetryCorrelation, or Microsoft.ApplicationInsights Remove the references. Some of these references are added by default from certain Visual Studio templates, and older versions of Visual Studio may add references to Microsoft.ApplicationInsights.
AppAlreadyInstrumented:true This value can also be caused by the presence of the above dlls in the app folder from a previous deployment. Clean the app folder to ensure that these dlls are removed.
AppContainsAspNetTelemetryCorrelationAssembly: true This value indicates that extension detected references to Microsoft.AspNet.TelemetryCorrelation in the application, and will back-off. Remove the reference.
AppContainsDiagnosticSourceAssembly**:true This value indicates that extension detected references to System.Diagnostics.DiagnosticSource in the application, and will back-off. Remove the reference.
IKeyExists:false This value indicates that the instrumentation key is not present in the AppSetting, APPINSIGHTS_INSTRUMENTATIONKEY. Possible causes: The values may have been accidentally removed, forgot to set the values in automation script, etc. Make sure the setting is present in the App Service application settings.

For the latest information on the Application Insights agent/extension, check out the release notes.

Next steps



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