IIS application pool is recycled every 20 minutes despite configuration

Question

I'm trying to disable application pool recycling and changed recycling interval in the app pool configuration to 0. Here's full configuration from .config:

<add name="DefaultAppPool" autoStart="true" managedRuntimeVersion="v4.0">
    <recycling logEventOnRecycle="Time, Memory, IsapiUnhealthy, OnDemand, ConfigChange, PrivateMemory">
        <periodicRestart time="00:00:00">
            <schedule>
                <clear />
            </schedule>
        </periodicRestart>
    </recycling>
</add>

Despite that application is still recycled several times a day which can be seen in the event log:

A worker process with process id of '1584' serving application pool 'DefaultAppPool' was shutdown due to inactivity. Application Pool timeout configuration was set to 20 minutes. A new worker process will be started when needed.

This happens on Azure Windows 2008 R2 VM with IIS 7.5. Is there anything else I need to do to make this setting work?

Answer 1

Possible duplicate of IIS: Idle Timeout vs Recycle and others.

What you are looking for is the idleTimeout which you will find under the process model element in applicationhost.config. Unless you have a strong case I would not recommend disabling the timeout as it is a primary mechanism for releasing unused resources when the site in question is not under load.

If it is idle and shuts down then there is a very small overhead as the new process is spooled up, if this is really an issue then I would suggest investigating some form of persisted cache such disk cache offered by the Application Request Routing IIS Module.