Troubleshooting HTTP 502.5 startup issues in Azure AppService for ASP.NET Core Websites


Whenever ASP.NET Core website fails to start in Azure AppService we get HTTP
502.5 error and this below error page


dotnet.http.5025.1

To troubleshoot this startup error, we need to capture addition logs.
Here are the steps to capture logs :
 

  1. Go to SCM site, just add .scm before .azurewebsites.net in
    the URL as shown below


    2018-05-10_13h41_03

  2. In the SCM website, click on the Debug Console | CMD
  3. Click on Site | WwwRoot folder
  4. Look for web.config file, now click on the pencil icon to edit it
  5. Change the web.config as highlighted below


    2018-05-10_13h35_29



    <aspNetCore
    processPath="dotnet"
    arguments=".\webapp.dll"
    stdoutLogEnabled="true"
    stdoutLogFile="\\?\%home%\LogFiles\stdout"
    >

    </aspNetCore>

  6. Now, try to browse to the home page of your website
  7. You should see same startup failure error message
  8. Go back to SCM website
  9. Navigate to d:\home\Logfiles
  10. You should now see stdout_xxx_datetime.log as shown below


    2018-05-10_13h39_43

  11. Click on the pencil icon to view it.
  12. You should see the callstack and line # of the exception
    as shown below


    2018-05-10_13h45_54


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