Redirect to different CDN based on GeoLocation

when HTTP_REQUEST {

 Disable the stream filter by default
STREAM::disable

 Check if the client IP is in the test_group data group or in China
if { ([matchclass [IP::client_addr] equals test_group]) or ( [whereis [IP::client_addr] country] equals "CN") } {
log local0. "User is in country [whereis [IP::client_addr] country]"
set CDN1 "example-s.cdn1.net"
set CDN2 "example-s.cdn2.net"
} else {
 Track that we will not rewrite the response content
set CDN1 ""
}
}
when HTTP_RESPONSE {

 Rewrite redirects
if  {[HTTP::is_redirect] and [HTTP::header Location] contains "$CDN1"}{
HTTP::header replace Location [string map "$CDN1 $CDN2" [HTTP::header Location]]
}
 Check if we are rewriting the response content
if {$CDN1 ne ""}{

 Set the find/replace for the stream filter and enable it
STREAM::expression "@$CDN1@$CDN2@"
log local0. "A user in country [whereis [IP::client_addr] country] has been redirected from CDN1 to CDN2"
STREAM::enable
}
} 
when STREAM_MATCHED {
log local0. "HOORAY"
}