iRule: redirect to pool based on app response time?

I would like to use an iRule to direct traffic based on the response time of the back-end resource pool. Under normal operations, incoming requests (these are SOAP-based queries) will go to the primary resource pool. When the primary pool becomes unresponsive (response slower than 5-10 seconds), requests should be directed to a secondary pool which is configured to basically tell the client "come back later".

 

 

I am using priority groups and health monitors to approximate this mechanism currently. But I think if I could find the right tools in iRule I would have more precise control.

 

 

Basically I need something like:

 

 

when HTTP_REQUEST {

 

 

[code to check response time here...]

 

 

if response_time < 10 {

 

pool primary_pool

 

return

 

}

 

else {

 

pool secondary_pool

 

return

 

}

 

}

 

 

Is there a command to test the back-end response? We are on BIG-IP 9.4.3

 

 

Thanks!