mkdir PowerShellAiAvailability cd PowerShellAiAvailabilityIf on Windows, use the NuGet CLI ([download page](https://www.nuget.org/downloads)) to install the [Application Insights SDK NuGet package](https://www.nuget.org/packages/Microsoft.ApplicationInsights/):
nuget install Microsoft.ApplicationInsights -Version 2.16.0 -o DependenciesThis command will create the 'Dependencies' folder, and then download and unpack the required packages to the folder. There are other ways to install NuGet packages, but you can always fall back to downloading the package manually from the NuGet gallery. To download the package, navigate to the [NuGet package page](https://www.nuget.org/packages/Microsoft.ApplicationInsights) and click on the link "Download package". The extension of the file will be "nupkg", but this is a simple zip-archive. Rename the extension to "zip" and unzip the archive. The DLL's can be found in the '*lib*' subfolder. Now that you have the AI SDK DLL's, create a PowerShell file '*CheckAvailability.ps1*' with the following contents:
$MyInvocation.MyCommand.Path | Split-Path | Push-Location; # Update the path if you install a different version of AI NuGet package Add-Type -Path .\Dependencies\Microsoft.ApplicationInsights.2.16.0\lib\netstandard2.0\Microsoft.ApplicationInsights.dll; $InstrumentationKey = $Env:APPINSIGHTS_INSTRUMENTATIONKEY; # If your resource is in a region like Azure Government or Azure China, change the endpoint address accordingly. # Visit https://docs.microsoft.com/azure/azure-monitor/app/custom-endpoints#regions-that-require-endpoint-modification $EndpointAddress = "https://dc.services.visualstudio.com/v2/track"; $Channel = [Microsoft.ApplicationInsights.Channel.InMemoryChannel]::new(); $Channel.EndpointAddress = $EndpointAddress; $TelemetryConfiguration = [Microsoft.ApplicationInsights.Extensibility.TelemetryConfiguration]::new( $InstrumentationKey, $Channel ); $TelemetryClient = [Microsoft.ApplicationInsights.TelemetryClient]::new($TelemetryConfiguration); $TestName = "AvailabilityTestFunction"; $TestLocation = $Env:COMPUTERNAME; # you can use any string for this $OperationId = (New-Guid).ToString("N"); $Availability = [Microsoft.ApplicationInsights.DataContracts.AvailabilityTelemetry]::new(); $Availability.Id = $OperationId; $Availability.Name = $TestName; $Availability.RunLocation = $TestLocation; $Availability.Success = $False; $Stopwatch = [System.Diagnostics.Stopwatch]::New() $Stopwatch.Start(); $OriginalErrorActionPreference = $ErrorActionPreference; Try { $ErrorActionPreference = "Stop"; # Run test $Response = Invoke-WebRequest -Uri "https://swimburger.net"; $Success = $Response.StatusCode -eq 200; # End test $Availability.Success = $Success; } Catch { # Submit Exception details to Application Insights $Availability.Message = $_.Exception.Message; $ExceptionTelemetry = [Microsoft.ApplicationInsights.DataContracts.ExceptionTelemetry]::new($_.Exception); $ExceptionTelemetry.Context.Operation.Id = $OperationId; $ExceptionTelemetry.Properties["TestName"] = $TestName; $ExceptionTelemetry.Properties["TestLocation"] = $TestLocation; $TelemetryClient.TrackException($ExceptionTelemetry); } Finally { $Stopwatch.Stop(); $Availability.Duration = $Stopwatch.Elapsed; $Availability.Timestamp = [DateTimeOffset]::UtcNow; # Submit Availability details to Application Insights $TelemetryClient.TrackAvailability($Availability); # call flush to ensure telemetry is sent $TelemetryClient.Flush(); $ErrorActionPreference = $OriginalErrorActionPreference; } Pop-Location;Let's dissect the code:
$MyInvocation.MyCommand.Path | Split-Path | Push-Location;If you execute the script while your current working directory (CWD) is in a different location, this line will change the CWD to the folder location of the script file. This will make sure relative paths will point to the correct files.
# Update the path if you install a different version of AI NuGet package Add-Type -Path .\Dependencies\Microsoft.ApplicationInsights.2.16.0\lib\netstandard2.0\Microsoft.ApplicationInsights.dll;The `Add-Type` command will load the specified DLL which is the Application Insights SDK. Make sure the path is correct in case you installed a different version or if you need to support a different [target framework moniker](https://docs.microsoft.com/en-us/dotnet/standard/frameworks) (TFM). Depending on the version of PowerShell and .NET on your machine, you may need to pick a different TFM.
$InstrumentationKey = $Env:APPINSIGHTS_INSTRUMENTATIONKEY;The above command fetches the Application Insights Instrumentation Key from the environment variables. **This env variable will be configured later.**
# If your resource is in a region like Azure Government or Azure China, change the endpoint address accordingly. # Visit https://docs.microsoft.com/azure/azure-monitor/app/custom-endpoints#regions-that-require-endpoint-modification $EndpointAddress = "https://dc.services.visualstudio.com/v2/track"; $Channel = [Microsoft.ApplicationInsights.Channel.InMemoryChannel]::new(); $Channel.EndpointAddress = $EndpointAddress; $TelemetryConfiguration = [Microsoft.ApplicationInsights.Extensibility.TelemetryConfiguration]::new( $InstrumentationKey, $Channel ); $TelemetryClient = [Microsoft.ApplicationInsights.TelemetryClient]::new($TelemetryConfiguration);The above snippet creates and configures the telemetry client which will be used to send the telemetry to Application Insights.
$TestName = "AvailabilityTestFunction"; $TestLocation = $Env:COMPUTERNAME; # you can use any string for this $OperationId = (New-Guid).ToString("N");The following variables will be sent for every piece of telemetry: - TestName: Pick any meaningful name, this will be shown in the availability dashboard - TestLocation: The out of the box availability tests will put their Azure region in there, but you can put anything in there that's meaningful to you. In this case, the variable is set to the computer's name also referred to as the hostname. This way you could identify which server or computer ran the test. - OperationId: Use a GUID to ensure this is a unique identifier, the output of
(New-Guid).ToString("N") looks like '4832d6822c4b4d378ffa566cc0fe28e0'.$Availability = [Microsoft.ApplicationInsights.DataContracts.AvailabilityTelemetry]::new(); $Availability.Id = $OperationId; $Availability.Name = $TestName; $Availability.RunLocation = $TestLocation; $Availability.Success = $False;This snippet creates an `AvailabilityTelemetry` object and configures it with the variables you just created. This is the object you need to submit to Application Insights.
$Stopwatch = [System.Diagnostics.Stopwatch]::New()
$Stopwatch.Start();
The snippet above creates a stopwatch and starts it. The stopwatch will be used to measure the time it takes to verify the availability.
$OriginalErrorActionPreference = $ErrorActionPreference; Try { $ErrorActionPreference = "Stop";The
$ErrorActionPreference is a variable always available in PowerShell and it determines the default error action preference for PowerShell commands which defaults to "Continue". When the error action preference is set to "Continue", it will output errors to the console, but just continue as if nothing happened. As a result, it won't jump to the catch clause which is undesired in this section of the script. Therefore the error action preference is changed to "Stop" which will make the script jump to the catch clause on error.
To undo the change to `$ErrorActionPreference` later, you need to store the original value in `$OriginalErrorActionPreference`.
# Run test $Response = Invoke-WebRequest -Uri "https://swimburger.net"; $Success = $Response.StatusCode -eq 200; # End test $Availability.Success = $Success; }Between the "Run test" and "End test" comment, you should perform whatever checks you need to verify the availability of your application. The verification in the above test is a simple HTTP request to my website and verifying whether the response status code is 200. That's essentially the same as what the built-in URL Ping test does, but you could replace this with selenium UI tests, database connection tests, etc. Whatever you can do with PowerShell you could use to verify availability. If an error occurs, the script jumps to the following catch clause:
Catch { # Submit Exception details to Application Insights $Availability.Message = $_.Exception.Message; $ExceptionTelemetry = [Microsoft.ApplicationInsights.DataContracts.ExceptionTelemetry]::new($_.Exception); $ExceptionTelemetry.Context.Operation.Id = $OperationId; $ExceptionTelemetry.Properties["TestName"] = $TestName; $ExceptionTelemetry.Properties["TestLocation"] = $TestLocation; $TelemetryClient.TrackException($ExceptionTelemetry); }In the catch clause, an `ExceptionTelemetry` object is created and initialized with the exception which just occurred. You have to use the same `$OperationId` for the `ExceptionTelemetry` so that Application Insights can relate telemetry instances with each other.
Finally { $Stopwatch.Stop(); $Availability.Duration = $Stopwatch.Elapsed; $Availability.Timestamp = [DateTimeOffset]::UtcNow; # Submit Availability details to Application Insights $TelemetryClient.TrackAvailability($Availability); # call flush to ensure telemetry is sent $TelemetryClient.Flush(); $ErrorActionPreference = $OriginalErrorActionPreference; } Pop-Location;Whether there was an error or not, the script will always run the statements inside the `Finally` clause. The stopwatch is stopped and the duration of the test is stored in the `Duration` property. The current time is also pushed into the `AvailabilityTelemetry` via the `Timestamp` property. The invocation of `$TelemetryClient.TrackAvailability` will queue the data submission to Application Insights. The data may or may not have been transmitted to Application Insights, but calling `$TelemetryClient.Flush()` will ensure it is sent. Finally, the error action preference is reversed to its original value and the CWD is reset to the original CWD. ## Testing out the custom PowerShell Availability Test {#testing-out-the-custom-powershell-availability-test} You will need the instrumentation key to send any Telemetry to Application Insights. To find this key, navigate to the Overview blade of your Application Insights resource and **copy the "Instrumentation Key":**
$Env:APPINSIGHTS_INSTRUMENTATIONKEY = "[INSERT_KEY_HERE]"
Once you close your shell, the environment variable will not be available anymore. Refer to this documentation if you want to save the environment variables permanently.
Invoke the script like this:.\CheckAvailability.ps1Run the script a couple of times to get multiple data points. Then navigate to the "Availability" blade of Application Insights in the Azure Portal and confirm the data is showing up:
Note: it can take a couple of minutes for the data to show up.
You probably want the availability test to run on a recurring basis. On Windows, you can configure a recurring Windows Task and on Linux, you can use the built-in crontab functionality.