10 Recycling IIS Application Pool Best Practices

IIS Application Pool Recycling is a process of periodically recycling the worker processes in an IIS application pool. This process helps to avoid issues that can occur when worker processes run for extended periods of time, such as memory leaks or other problems that can cause the worker process to become unstable.

There are a number of best practices that should be followed when recycling IIS application pools. This article will discuss 10 of those best practices.

1. Recycle IIS Application Pool on a Schedule

When an IIS Application Pool is recycled, all of the currently running worker processes in that pool are terminated. This means that any in-memory data or cached data that those worker processes were using will be lost.

If you recycle IIS Application Pool on a schedule, you can minimize the impact of this data loss by only recycling during periods of low activity. For example, you could recycle IIS Application Pool every night at 2am.

Recycling IIS Application Pool on a schedule also allows you to take advantage of any new features or bug fixes that have been made to the application since the last time it was recycled.

2. Recycle IIS Application Pool when Memory Usage Exceeds Limit

When an IIS Application Pool is left running for extended periods of time, it can start to consume more and more memory. This is due to the fact that each new request that comes in requires some amount of memory to process. If the application pool is not recycled on a regular basis, this can lead to memory leaks and eventually OutOfMemoryException errors.

One way to avoid these types of errors is to recycle the application pool when memory usage exceeds a certain limit. By doing this, you can ensure that the application pool does not consume too much memory and cause problems for your server.

3. Recycle IIS Application Pool When Virtual Memory is Low

When virtual memory is low, it means that the server is under heavy load and is starting to struggle. By recycling the application pool, you’re essentially giving the server a fresh start, which can help reduce the load and improve performance.

Of course, this isn’t a cure-all solution, and if the server is consistently struggling with low virtual memory, then there’s likely a bigger problem that needs to be addressed. However, in many cases, recycling the application pool when virtual memory is low can help improve performance and stability.

4. Recycle IIS Application Pool When Physical Memory is Low

When physical memory is low, the system starts to page out application pool memory to the disk, which can cause performance degradation. By recycling the application pool when physical memory is low, you can avoid this issue.

Additionally, recycling the application pool can help clear up any memory leaks that may have developed. Memory leaks can cause an application pool to consume more and more memory over time, eventually leading to performance issues.

Finally, recycling the application pool can also help clear up any stale data that may be stored in memory. Stale data can cause an application pool to return incorrect results or fail to function properly.

5. Recycle IIS Application Pool When an Unhandled Exception Occurs

When an unhandled exception occurs, it usually means that there is a bug in the code that needs to be fixed. By recycling the application pool, you are essentially resetting the state of the application, which gives you a chance to fix the bug and prevent it from happening again.

It’s also a good idea to recycle the application pool on a regular basis, even if there are no unhandled exceptions. This will help keep the application running smoothly and prevent any potential issues from arising.

6. Recycle IIS Application Pool When the Worker Process has been Running for a Specified Time

When an IIS application pool is recycled, all of the currently running worker processes in that pool are terminated. This means that any in-memory data or cached data that those worker processes were using will be lost.

However, if the worker process has been running for a long time, it’s likely that that data is no longer valid anyway. For example, if you have an IIS application pool that is used to serve up web pages, then the data in the worker process’ memory is likely to be HTML files that have already been served to the client and are no longer needed.

By recycling the IIS application pool on a regular basis, you can ensure that the worker processes are not holding onto stale data.

7. Recycle IIS Application Pool When the Number of Requests Exceeds a Specified Number

When an IIS Application Pool is recycled, all of the currently executing requests are completed, and then the pool is restarted. This means that any in-memory data that has been cached by the application will be lost.

If the number of requests exceeds a certain threshold, it’s likely that the application is starting to experience performance issues due to memory leaks or other problems. By recycling the application pool when this happens, you can help prevent these issues from getting worse and impacting the stability of the server.

It’s important to note that recycling the application pool will cause a brief interruption in service, so it’s important to choose a threshold that won’t cause too much disruption for your users.

8. Recycle IIS Application Pool When Config File Changes

When you make changes to the config file, those changes will not take effect until you recycle the application pool. This is because IIS reads the config file when the application pool starts up, and if there are any changes, it will use the new settings.

If you don’t recycle the application pool after making changes to the config file, then your changes will not take effect until the next time the application pool recycles itself, which could be days or weeks later.

So, to ensure that your changes take effect immediately, recycle the application pool after making changes to the config file.

9. Recycle IIS Application Pool When Machine Key Changes

When you change the machine key, it invalidates all of the existing sessions and cookies. This means that any user who was logged in will be logged out, and any data that was stored in a session or cookie will be lost.

If you don’t recycle the application pool when you change the machine key, then users will experience errors and unexpected behavior, and data could be lost.

To avoid these problems, it’s best to recycle the application pool whenever you change the machine key. This way, users will be able to login and use the site as expected, and no data will be lost.

10. Recycle IIS Application Pool When Private Memory Limit Exceeded

When an IIS Application Pool is recycled, all of the currently active requests are completed, and then the pool is restarted. This means that any in-memory data that has been accumulated by the application will be lost.

If the application is constantly accumulating more and more data in memory, eventually it will reach a point where the amount of data is so large that it will start impacting performance. At this point, recycling the application pool will help to clear out the data and improve performance.

It’s important to note that you should only recycle the application pool when the private memory limit is exceeded. If you recycle the application pool too frequently, it can impact the stability of the application.