IIS Application Pool Performance Tuning

While monitoring your servers you may see increased memory consumption due to the surveys or services being loaded into memory. As *32 processes (i.e. any 32-bit process running on a 64-bit Windows OS) cannot allocate more than 4GB of memory, you may have to recycle the IIS process from time to time; especially for busy environments. This limit is noticeable for .NET Framework applications as the effective memory limit becomes approximately 50 – 60% of the maximum process memory size.

Forsta operates three Software-as-a-Service sites. The following recycle recommendations are adapted from our current environments. Other recommendations may apply in environments with different memory specifics.

Configuration

How to set up the ConfirmitWIXAppPool recycle settings:

Figure 1 - The Recycling Conditions page

1. Disable Regular time interval recycling.
2. Enable Private memory usage recycling, and set to 1536000 (which equals 1546MB).
Note: you should monitor each server’s virtual bytes and private bytes for the w3wp.exe processes to ensure that they are not recycled too soon or too late. If the server runs into ‘OutOfMemory’ exceptions, reduce this value. If the server recycles frequently without any errors, consider increasing this value and decreasing the SurveyPackageSlidingExpiration value in Forsta Plus.
3. Click Next to continue.



Figure 2 - The Advanced Settings page - 1

4. Disable Idle Time-out (minutes) to prevent worker processes from shutting down if they have no work to do.

This option could have some small performance effects, but these will be most likely for systems with little traffic (most usual for other application pools than those handing surveys). Setting the value to 0 will disable idle time-outs.



Figure 3 - The Advanced Settings page - 2

5. Disable rapid-fail protection to prevent the application pool from shutting down automatically in the event of crashes.

With the setting disabled, a new worker process will be started repeatedly. If the worker process is shut down, all surveying will stop until the process is manually restarted.

Note: Disabling the fail protection merely bypasses the internal protection feature within IIS; it does not correct the cause of the errors.
6. Within Forsta Plus we set the SurveyPackageSlidingExpiration to 15 minutes site-wide to prevent idle surveys from occupying memory unnecessarily. Go to Admin > System Configuration > Deployment.



Figure 4 - The SurveyPackageSlidingExpiration Value

7. For each survey server under, reset the SurveyPackageSlidingExpiration to the default value to make it inherit the role setting (which is now set to 15 in the step above).

Other Application Pool Recommendations

Authoring Servers:

• ConfirmitAuthorAppPool
• Idle Time-out (minutes): 0 (original 20)
• Recycling
  • Private Memory Limit (KB): 1536000
  • Regular Time Interval (minutes): 0

Reportal Servers:

• ConfirmitReportalAppPool

• Idle Time-out (minutes): 0
• Recycling

• Private Memory Limit (KB): 1536000
• Regular Time Interval (minutes): 0

Web Service Servers:

• ConfirmitApiAppPool
• Idle Time-out (minutes): 0
• Shutdown Time Limit (seconds): 300
• Recycling
  • Private Memory Limit (KB): 1536000
  • Regular Time Interval (minutes): 0