IIS App Pool Shows “Running” but Site Becomes Unresponsive Until Manual Recycle

Hello Captain56022,

Thanks for sharing the context. Based on the settings you shared and what I saw when researching the internet, this could be what’s happening:

Your application pool seems to be entering Rapid-Fail Protection mode because the worker process (w3wp.exe) may be crashing repeatedly. The default for IIS is 5 failures in 5 minutes. 

Even if the pool still shows “Running” in the GUI, once those failures trigger the protection IIS will stop serving requests, so the site becomes effectively unreachable. 

If I were you, here’s what I’d try to check first (just to confirm or rule out this cause):

• Look into Windows Event Viewer (System and Application logs) around the time the outage happened, check for “worker process terminated unexpectedly,” “fatal communication error,” or “application pool … disabled due to a series of failures.” That’ll show whether Rapid-Fail Protection was triggered. 
• If you find such failures, you could temporarily disable Rapid-Fail Protection (for testing only) to see if the site stays up, but this is only a diagnostic step, not a fix. 
• Ultimately you need to identify what’s causing the crashes (bad code, config, dependencies, module load issues, identity problems, etc.) and fix that root problem. 

Hope this helps.

It sounds like you're experiencing an issue where the IIS application pool is showing as "Running" but the site becomes unresponsive, requiring a manual recycle or restart of IIS to restore functionality. Here are some potential troubleshooting steps and considerations based on similar issues:

1. Check Application Pool Settings: Ensure that the application pool is configured correctly. Sometimes settings like idle timeout or recycling settings can cause unexpected behavior. You might want to check if the application pool is set to recycle after a certain period of inactivity.
2. Review Event Logs: Check the Windows Event Viewer for any warnings or errors related to IIS or the application pool. This can provide clues about what might be happening when the site becomes unresponsive.
3. Use Debug Diagnostics Tool: Consider using the Debug Diagnostics Tool to analyze the application pool when it becomes unresponsive. This tool can help identify memory leaks or other issues that might not be apparent through standard monitoring.
4. Monitor Requests: Enable Request Monitor in IIS to track incoming requests and see if there are any patterns or specific requests that lead to the application pool becoming unresponsive.
5. Analyze Performance Metrics: Although you mentioned that CPU, RAM, Disk, and Network usage are normal, consider using Performance Monitor (Perfmon) to gather more detailed metrics during the times the application pool becomes unresponsive. This can help identify any unusual spikes or trends.
6. Check for Deadlocks: If your application is using databases or external resources, check for potential deadlocks or long-running queries that might be causing the application to hang without consuming significant resources.
7. Review Code Changes: If this issue started occurring after recent code changes, review those changes for any potential issues that could lead to unresponsiveness under low traffic conditions.

Since the problem is random and occurs specifically during low traffic, it may be related to how the application handles idle states or resource management when not under load.

References:

• Troubleshooting High CPU in an IIS application pool
• Troubleshoot native memory leak in an IIS 7.x application pool