Azure App Service diagnostics is an intelligent and interactive experience to help you troubleshoot your web app with no configuration required. When you do run into issues with your web app, App Service diagnostics will point out what’s wrong to guide you to the right information to more easily and quickly troubleshoot the issue.
Although this experience is most helpful when you’ve been having issues with your web app within the previous 24 hours, all the diagnostic graphs will be available for you to analyze at all times.
More information about App Service diagnostics, as well as additional troubleshooting tools and links to helpful documentation and forums, are located here.