Why Your Application Pool May Not Recycle at Defined Intervals: Common Causes and Solutions

Have you ever wondered why your application pools sometimes don’t recycle according to specified conditions (e.g. regular time intervals or specific schedules)? There can be a variety of reasons behind this unexpected behavior. In this article, we will look at the most common causes of this problem.

problem

In the context of this discussion, we have set the recycling condition to occur every 60 minutes. Ideally, the application pool should automatically recycle at these regular intervals.

You can check the recycling event in the system event log. As you can see in the image below, there is a worker process with process ID ‘ in the WAS source.‘, providing application pool ‘‘ has requested recycling because the allowed processing time limit has been reached.

However, in some cases, this event may not appear, or the application pool may not be recycled at the scheduled time or under the specified conditions. The most common reason for this is that the worker process may have already been terminated due to inactivity or other factors. To check this, check the advanced settings of the application pool and review the idle timeout settings.

Now find the events in your WAS source and check if there is an entry called “Worker process with process ID ‘”.‘Providing application pool’‘ has been terminated due to inactivity. The application pool timeout configuration is set to 20 minutes. A new worker process will be started when needed.”

You need to make sure that there are no requests between the time the application pool is shut down and the scheduled recycle time. This will ensure that there are no worker processes running to handle requests during that time period. You can check this by reviewing the IIS logs. I won’t go into detail here, but analyzing the IIS logs can be a separate topic for discussion.

cause
In summary, if the worker process is not running, recycle conditions for regular intervals or specific times will not trigger an application pool recycle.

conclusion
In conclusion, to understand why an application pool is not being recycled according to the defined conditions, you need to comprehensively examine several factors. A variety of issues can cause it not to be recycled as expected. The most common cause is worker process termination due to inactivity, which can cause the application pool to not be recycled at the scheduled time.

You can check the System Event Log for related events and check the Idle Time-out setting in the Advanced Settings of the application pool to determine if inactivity or other issues are affecting the recycling process. You can also review the IIS logs to determine if any requests were made between the shutdown and the scheduled recycling time, which will help determine if there were no worker processes to handle the requests.

Ultimately, if the worker process is not running, the application pool’s recycling conditions will not be triggered, and recycling will not occur. Addressing these issues and ensuring proper configuration can help maintain the stability and performance of your application pool.