HTTP Session Limit
Problem this snippet solves:
Limits total concurrent HTTP sessions to a pre-defined threshhold, allowing those clients with a session cookie to continue once the limit is reached, while redirecting new clients until concurrent sessions are again below the theshhold.
Code :
rule HTTP_session_limit {
when RULE_INIT {
set ::total_active_clients 0
set ::max_active_clients 100
log local0. "rule session_limit initialized: total/max: $::total_active_clients/$::max_active_clients"
}
when HTTP_REQUEST {
;# test cookie presence
if {[HTTP::cookie exists "ClientID"]} {
set need_cookie 0
set client_id [HTTP::cookie "ClientID"]
;# if cookie not present & connection limit not reached, set up client_id
} else {
if {$::total_active_clients < $::max_active_clients} {
set need_cookie 1
set client_id [format "%08d" [expr { int(100000000 * rand()) }]]
# Only count this request if it's the first on the TCP connection
if {[HTTP::request_num] == 1}{
incr ::total_active_clients
}
;# otherwise redirect
} else {
HTTP::redirect "http://sorry.domain.com/"
return
}
}
}
when HTTP_RESPONSE {
;# insert cookie if needed
if {$need_cookie == 1} {
HTTP::cookie insert name "ClientID" value $client_id path "/"
}
}
when CLIENT_CLOSED {
;# decrement current connection counter for this client_id
if {$::total_active_clients > 0} {
incr ::total_active_clients -1
}
}
}Published Mar 18, 2015
Version 1.0
