Application Insights overview

Application Insights is a feature of Azure Monitor that provides extensible application performance management (APM) and monitoring for live web apps. Developers and DevOps professionals can use Application Insights to:

Automatically detect performance anomalies.
Help diagnose issues by using powerful analytics tools.
See what users actually do with apps.
Help continuously improve app performance and usability.

Application Insights:

Supports a wide variety of platforms, including .NET, Node.js, Java, and Python.
Works for apps hosted on-premises, hybrid, or on any public cloud.
Integrates with DevOps processes.
Has connection points to many development tools.
Can monitor and analyze telemetry from mobile apps by integrating with Visual Studio App Center.

How Application Insights works

To use Application Insights, you either install a small instrumentation package (SDK) in your app, or enable Application Insights by using the Application Insights agent. For languages and platforms that support the Application Insights agent, see Supported languages. https://docs.microsoft.com/en-us/azure/azure-monitor/app/asp-net

You can instrument the web app, any background components, and the JavaScript in the web pages themselves. The app and its components don't have to be hosted in Azure.

The instrumentation monitors your app and directs the telemetry data to an Application Insights resource by using a unique instrumentation key. The impact on your app's performance is small. Tracking calls are non-blocking, and are batched and sent in a separate thread.

You can pull in telemetry like performance counters, Azure diagnostics, or Docker logs from host environments. You can also set up web tests that periodically send synthetic requests to your web service. All these telemetry streams are integrated into Azure Monitor. In the Azure portal, you can apply powerful analytics and search tools to the raw data.

The following diagram shows how Application Insights instrumentation in an app sends telemetry to an Application Insights resource.

What Application Insights monitors

Application Insights helps development teams understand app performance and usage. Application Insights monitors:

Request rates, response times, and failure rates

Find out which pages are most popular, at what times of day, and where users are. See which pages perform best. If response times and failure rates are high when there are more requests, there might be a resourcing problem.
Dependency rates, response times, and failure rates, to show whether external services are slowing down performance
Exceptions

Analyze the aggregated statistics, or pick specific instances and drill into the stack trace and related requests. Application Insights reports both server and browser exceptions.
Page views and load performance reported by users' browsers
AJAX calls from web pages, including rates, response times, and failure rates
User and session counts
Performance counters from Windows or Linux server machines, such as CPU, memory, and network usage
Host diagnostics from Docker or Azure
Diagnostic trace logs from apps, so you can correlate trace events with requests
Custom events and metrics in client or server code that track business events, like items sold