Monday, April 20, 2020

How to profile ASP.NET apps using Application Insights

Application Insights can monitor, log, alert and even help us understand performance problems with our apps.
Photo by Marc-Olivier Jodoin on Unsplash
We've been discussing AppInsights in depth on this blog and to complete the series, I'd like to discuss the performance features it offers. On the previous posts, we learned how to collect, suppress and monitor our applictions using AppInsights data.

On this post let's understand how to use the performance features to identify and fix performance problems with our app.

What's profiling?

Wikipedia defines profiling as:
a form of dynamic program analysis that measures, for example, the space (memory) or time complexity of a program, the usage of particular instructions, or the frequency and duration of function calls. Most commonly, profiling information serves to aid program optimization.
Profiles usually monitor:
  • Memory
  • CPU
  • Disk IO
  • Network IO
  • Latency
  • Speed the of application
  • Access to resources
  • Databases
  • etc

Profiling ASP.NET Applications

ASP.NET developers have multiple ways of profiling our web applications, being the most popular: 
Those are awesome tools that definitely you should use. But today we'll focus on what can we do to inspect our deployed application using Application Insights.

How can Application Insights help

Azure Application Insights collects telemetry from your application to help analyze its operation and performance. You can use this information to identify problems that may be occurring or to identify improvements to the application that would most impact users. This tutorial takes you through the process of analyzing the performance of both the server components of your application and the perspective of the client so you understand how to:
  • Identify the performance of server-side operations
  • Analyze server operations to determine the root cause of slow performance
  • Identify slowest client-side operations
  • Analyze details of page views using query language

Using performance instrumentation to identify slow resources

Let's illustrate how to detect performance bottlenecks in our app with some some. The code for this exercise is available on my github. You can quickly get it by:
git clone
cd aspnet-ai
git branch performance
# insert your AppInsights instrumentation key on appSettings.Development.json
dotnet run
This project contains 5 endpoints that we'll use to simulate slow operations:
  • SlowPage - async, 3s to load, throws exception
  • VerySlowPage - async, 8s to load
  • CpuHeavyPage - sync, loops over 1 million results with 25ms of interval
  • DiskHeavyPage - sync, writing 1000 lines to a file
 Running the tool and get back to azure. We should have some data there.

Performance Tools in AppInsights

Our AppInsights resource in Azure greets us with an overview page already that shows us consolidaded information about failed requests, server response time, server requests and availability:

Now, click on the Performance section. Out of the box, AppInsights has already captured previous requests and shows a consolidated view. Look below to already see our endpoints sorted out by duraction:

You should also have access to an Overall panel where you'd see requests per time:
There's also good stuff on the The End-to-end transaction details widget:

For example, we could click on a given request and  get additional information about it:


We now know which are the slowest pages on our site, let's now try to understand why. Essentially, have two options:
  1. use AppInsights's telemetry api (as on this example) 
  2. or integrating directly to your logging provider, using System.Diagnostics.Trace on this case.

Tracing with AppInsights SDK

Tracing with AppInsights SDK is done via the TrackTrace method from TelemetryClient class an is as simple as:
public IActionResult Index()
    return View();

Tracing with System.Diagnostics.Trace

Tracing with System.Diagnostics.Trace is also not complicated but requires the NuGet package Microsoft.ApplicationInsights.TraceListener. For more information regarding other logging providers, please check this page. Let's start by installing it with:
dotnet add package Microsoft.ApplicationInsights.TraceListener --version 2.13.0

C:\src\aspnet-ai\src>dotnet add package Microsoft.ApplicationInsights.TraceListener --version 2.13.0
  Writing C:\Users\bruno.hildenbrand\AppData\Local\Temp\tmpB909.tmp
info : Adding PackageReference for package 'Microsoft.ApplicationInsights.TraceListener' into project 'C:\src\aspnet-ai\src\aspnet-ai.csproj'.
info : Restoring packages for C:\src\aspnet-ai\src\aspnet-ai.csproj...
info : Installing Microsoft.ApplicationInsights 2.13.0.
info : Installing Microsoft.ApplicationInsights.TraceListener 2.13.0.
info : Package 'Microsoft.ApplicationInsights.TraceListener' is compatible with all the specified frameworks in project 'C:\src\aspnet-ai\src\aspnet-ai.csproj'.info : PackageReference for package 'Microsoft.ApplicationInsights.TraceListener' version '2.13.0' added to file 'C:\src\aspnet-ai\src\aspnet-ai.csproj'.
info : Committing restore...
info : Writing assets file to disk. Path: C:\src\aspnet-ai\src\obj\project.assets.json
log  : Restore completed in 4.18 sec for C:\src\aspnet-ai\src\aspnet-ai.csproj.

Reviewing the results

Back in Azure we should now see more information about the performance of the pages:
And more importantly, we can verify that our traces (in green) were correctly logged:

Where from here

If you used the tools cited above, you now should have a lot of information to understand how your application performs on production. What next?

We did two important steps here: understood the slowest pages and added trace information to them. From here, it's with up to you. Start by identifying the slowest endpoints and add extra telemetry on them. The root cause could be in a specific query in your app or even on an external resource. The point is, each situation is peculiar and extends the scope of this post. But the essential you have: which are the pages, methods and even calls that take longer. On that note, I'd recommend adding custom telemetry data so you have a real, reproducible scenario.


On this post, the last on the discussion about AppInsights, we reviewed how Application Insights can be used to understand, quantify and report about the performance or our apps. Once again, AppInsights demonstrates to be an essential tool for developers using Azure.

More about AppInsights

For more information, consider reading my previous articles about App Insights:
  1. Adding Application Insights telemetry to your ASP.NET Core website
  2. Suppressing Application Insights telemetry on .NET applications
  3. Monitoring ASP.NET applications using Application Insights and Azure Alerts


See Also

For more posts about AppInsights, please click here.

Connect with me:

Bruno Hildenbrand      
Software Engineer and open-source enthusiast.
.NET, Go, Linux, Vim, Cloud, Architecture, Docker & Kubernetes.