Iis Dll Asp Classic Crash

Resolving IIS 6 and COM+ Hangs: A Guide to Stabilizing Your Web Applications

If you’re managing a web application that utilizes IIS 6 and COM+ objects, you may have run into the frustrating issue of the application hanging under heavy load. In this post, we will discuss the underlying causes of this issue and provide effective strategies to resolve it.

The Problem: Application Hangs Under Load

When a web application hangs, it can severely impact user experience and lead to significant downtime. In one case, a Classic ASP application built using VBScript was reported to hang frequently, requiring the manual termination of the dllhost.exe process to restore functionality. The server environment in question is:

  • Processor: Intel Core 2 Duo 2.2 GHz
  • RAM: 4 GB
  • OS: Windows Server 2003 Web Edition SP2
  • Web Server: IIS 6.0

The web application leverages several COM+ objects, and there have been error entries related to these objects in the event log. But why do these COM object errors lead to such significant issues?

Understanding the Causes

1. COM Object Issues

COM+ objects can lead to hangs if:

  • They are not thread-safe when loaded into the application.
  • They are improperly used and discarded on each request.

2. Server Resource Limits

Given the hardware specifications, the server may struggle to handle high traffic or resource-intensive operations. Only having 4 GB of RAM can quickly become a bottleneck under heavy loads.

3. Outdated Technology

IIS 6.0 is quite dated. Upgrading to a newer version, such as IIS 7.0, could offer more stability and better handling of heavy loads. While IIS 7 is generally more stable, it’s essential to analyze specifically how the application behaves under the new environment.

Solutions to Consider

1. Debugging COM Objects

To effectively resolve the hanging issue:

  • Identify Problematic COM Objects: Use the divide and conquer technique to isolate the COM object causing the hangs. Set up a controlled environment with extensive logging to try and replicate the problem.
  • Thread Safety: Ensure that the COM objects you are using are thread-safe. If they are not, consider redesigning the access strategy to avoid concurrent access.

2. Implementing Automatic Recycling

If you opt for a quick fix:

  • Scheduled Application Recycling: Consider recycling the application every few hours. While this doesn’t eliminate the root cause, it will help to temporarily hide the symptoms of the problem and maintain better uptime.

3. Upgrade to a Newer IIS Version

Transitioning to IIS 7.0 can provide improved stability and features that help in managing application loads. Here’s what to keep in mind:

  • Evaluate Compatibility: Ensure that your application and COM components are compatible with the newer IIS version.
  • Testing: Conduct thorough testing on a staging server before rolling out the new version to production.

Conclusion

In the face of hanging issues with IIS 6 and COM+ applications, it’s crucial to investigate the underlying causes thoroughly. Debugging your COM objects, implementing automatic recycling, and considering an upgrade could be key strategies to achieving a stable web application environment. Remember that while temporary fixes can alleviate some symptoms, addressing the root issues will lead to lasting stability.

By taking the above steps, you can ensure a smoother experience for your users and a healthier environment for your application. Don’t forget to set up automated tests to continuously monitor application performance and stability.