In Chapter 7, Troubleshooting and Debugging, you learned how to add logging to your application and then query it with Application Insights on your local development machine. When moving to the cloud and dealing with multiple services and instances of them, you need a central location in which you can query all log messages, monitor the behavior of your entire system, and define alerts for anomalies in system components. This is where Azure Application Insights shines.
Application Insights can monitor any type of application–backend services or frontend applications. Once you configure it to your App Service, it collects telemetry on requests and failure rates, usage statistics, exceptions, and different flavors of availability and performance.