Fixing Docker IIS Container's 500 Server Error

Table of Contents

1. Introduction
2. Application Architecture
3. Error Analysis
4. Troubleshooting 500 Internal Server Error
   1. Verifying IIS Web Services
   2. Checking Application Pool
   3. Checking Event Logs
   4. Analyzing IIS Log
   5. Identifying the Cause
   6. Updating Web.Config File
   7. Redeploying Web.Config File
   8. Testing the Application
5. Conclusion
6. FAQs

Troubleshooting 500 Internal Server Error on IIS Container

Troubleshooting errors in a microservices. NET application with IIS and Docker containers can be tricky. The application architecture of such a system is complex and involves several moving parts that need to work together seamlessly. In this article, we will explore the possible causes for a 500 Internal Server Error encountered on an IIS container and go through the steps to troubleshoot and fix it.

Application Architecture

In our example, We Are running an ASP.NET 4.6 web application that is split into multiple microservices, each running in its container. There are three containers in total: one for the ASP.NET 4.6 framework and two for the MS Equal services. The web application is hosted on IIS, and the .NET Framework is 4.6.2. The application is connecting to an MS Equal database on two of the containers. The web application is listening on port 80, with an IP address.

Error Analysis

Upon accessing the application on the browser, it throws a 500 Internal Server Error. Checking the container blocks reveals no error or warning logs. The sequel container appears to be working fine, with the database successfully attached and started. Lastly, the web container appears to be clean. We could connect to the web container and verify that IIS web services are running as expected. We also checked the physical path of the Website and found that the content of the application is located in the correct location.

Troubleshooting 500 Internal Server Error

Verifying IIS Web Services

We verified that the correct IIS web services were up and running by using the following command:

& 'C:\Windows\system32\inetsrv\appcmd.exe' list apppools

Checking Application Pool

We confirmed that all application pools were running by using the following command:

& 'C:\Windows\system32\inetsrv\appcmd.exe' list wp

Checking Event Logs

We checked the event logs on the container to find any Relevant information that could help troubleshoot the 500 Internal Server Error. Using the following command, we listed all the event logs on the container:

Get-EventLog -LogName *

We also looked at the top 15 system event logs but found no relevant information.

Analyzing IIS Log

We examined the IIS log for the application to get more information about the error. The path to the log file is:

C:\inetpub\logs\LogFiles\W3SVC1\u_exYYMMDD.log

Extracting the last ten lines of the log file using the following command provided information about the error:

Get-Content -Path "C:\inetpub\logs\LogFiles\W3SVC1\u_exYYMMDD.log" | Select-Object -Last 10

Identifying the Cause

We found that the error was a 500 error with a 19 sub-error code. Looking up the definition of this code on Google, we found that it was due to a misconfigured or duplicate value in the web.config file. We scanned the web.config file of the application and found the error – a duplicate value of customError was set to off.

Updating Web.Config File

We updated the web.config file of the application and removed the duplicate value.

Redeploying Web.Config File

We redeployed the updated web.config file on the project and ran the container again.

Testing the Application

We tested the fixed application on the browser and found that the 500 Internal Server Error was fixed. However, we encountered a new error regarding database connectivity, which we need to troubleshoot further.

Conclusion

Troubleshooting a 500 Internal Server Error in an IIS container can be a daunting task. However, following the proper troubleshooting steps can help identify the error's root cause and fix it. It is essential to verify IIS web services and application pools' status, check event logs, analyze IIS logs, identify the cause, update the web.config file, and redeploy it.

FAQs

What is a 500 Internal Server Error?

A 500 Internal Server Error is an HTTP status code that indicates that the server encountered an unexpected error or condition that prevented it from fulfilling the request.

What are some common causes of a 500 Internal Server Error?

Common causes of a 500 Internal Server Error include server misconfigurations, wrong permissions, corrupted files, and faulty coding.

How do you troubleshoot a 500 Internal Server Error?

To troubleshoot a 500 Internal Server Error, You need to verify the server's web services and application pool statuses, check the event logs, analyze the server logs for the error, identify the cause, and fix it.