iRule adding 10% CPU overhead

I have formatted the iRule so that it is readable.

 

when HTTP_REQUEST priority 1 {

 

set static::maxActiveClients "[class search -all -value datagroup_selfridges_waitingroom starts_with "max_active_clients"]"

 

set subtableName "sessionLimit"

 

set sessionCookieName "[class search -all -value datagroup_selfridges_waitingroom starts_with "session_cookie_prefix"]"

 

set holdingPage "[class search -all -value datagroup_selfridges_waitingroom starts_with "holding_page_url"]"

 

set static::sessionTimeout "[class search -all -value datagroup_selfridges_waitingroom starts_with "session_timeout"]"

 

set need_cookie 0

 

if {[HTTP::cookie exists $sessionCookieName]} {

 

set client_id [HTTP::cookie $sessionCookieName]

 

set sessiondata [table lookup -subtable $subtableName $client_id]

 

if { $sessiondata != "" } {

 

log local0. "Valid session $client_id - continuing"

return

 

}

 

}

 

log local0. "No session. Checking for free slot (Max $static::maxActiveClients)"

set sessionCount [table keys -subtable $subtableName -count]

 

log local0. "No session. Checking for free slot (Current $sessionCount)"

if {$sessionCount < $static::maxActiveClients} {

 

set need_cookie 1

 

set client_id [format "%08d" [expr { int(1000000000 * rand()) }]]

 

set sessionValue [IP::client_addr]

 

table add -subtable $subtableName $client_id $sessionValue $static::sessionTimeout

 

log local0. "New Session ($client_id) added value $sessionValue Timeout static::sessionTimeout"

} else {

 

HTTP::redirect $holdingPage

 

}

 

}

 

when HTTP_RESPONSE priority 1 {

 

if {$need_cookie == 1} {

 

HTTP::cookie insert name $sessionCookieName value $client_id path "/"

 

}

 

}