basic persistence functional behavior question

I am new to load balancers. The code below is for jsessionid persistence. What is the code actually doing here ? I'm having difficulty understanding how persistence is actually used in this context. Does persistence of some value (jsessionid) imply that subsequent requests that contain the same value for jsessionid will be routed to the same server as the initial request? And oppositely, that if a request comes in with a jsessionid that has not yet been persisted, that value gets persisted and the request is routed to whatever server load balancing algorithm determines.

 

 

I'm just not seeing the explicit routing in the code below so I think I'm missing some basic functional concept.

 

 

Thanks, Patrick

 

 

 

when HTTP_REQUEST {

 

 

if { [string length [HTTP::cookie exists "JSESSIONID"]] } {

 

 

Persist off of the cookie value

 

persist uie [HTTP::cookie "JSESSIONID"] 3600

 

 

} else {

 

 

Parse the jsessionid from the path

 

set jsess [findstr [string tolower [HTTP::path]] "jsessionid=" 11]

 

 

Use the jsessionid from the path for persisting

 

if { $jsess != "" } {

 

 

persist uie $jsess 3600

 

 

}

 

}

 

}

 

when HTTP_RESPONSE {

 

 

Check if there is a jsessionid cookie in the response

 

if { [string length [HTTP::cookie exists "JSESSIONID"]] } {

 

 

Persist off of the cookie value

 

persist uie [HTTP::cookie "JSESSIONID"] 3600

 

 

}

 

}