Handle more than one application with one virtual server

I follow. I was just being a bit thick about the actual thing that is persisted (the pool member, not the pool). So, you can do this:

when HTTP_REQUEST {
  if { [HTTP::uri] starts_with "/new-app" } {
     set new_app 1
     pool new-app
  }
  elseif { [HTTP::cookie exists NewAppPath] } {
     pool new-app 
  }
}

when HTTP_RESPONSE {
    if { [info exists NewAppPath] } {
        HTTP::cookie insert name NewAppPath value true path /
    }
}

You must use OneConnect or add an

LB::detach

for Keep-Alive values to work, as noted by somebody else above. What this does is set a second cookie -- NewAppPath -- when the first condition is met. If later that cookie is present (we don't really care about the value), then the

new-app

pool is selected again.