HELP!!!!!!!!!!!, Got Crazy of Session persistence with irule and cookie

To answer your question first, no there is no such persistence that will do this out of the box - the idea with persistence is that you should be able to have different persistence entries for different pool members depending of which pool is selected. So in order to do this we must do some custom persistence to make it happen.

Now for the solution. At first I had some quite elaborate code to take care of this but once I started wrapping my head around the solution I realized that it was actually a lot easier than that - all we need to do is to add another cookie once pool2 has been selected and the presence of this cookie should then force the BIG-IP to henceforth send the traffic to pool2.

I also made use of variables to set the pool name, URI and so on, since I suspect that "pool2" isn't the actual name of the pool in your implementation, so this makes it easier for you to change the pool name according to your configuration. So this is what I've got:

when RULE_INIT {
    This variable defines the name of the custom cookie sent to
    the client to keep track of that this user should persist to
    the secondary pool only.

   set static::St_Cookie "mycookie"

    This variable contains the name of the pool to which the client
    should stick once it has been selected
    *** IMPORTANT ***
    This MUST be the full name, including partition - for example
    "/Common/pool2" - otherwise the iRule will not work as intended

   set static::Pool_Name "/Common/pool2"

    This is the URI that signifies that the secondary pool should be
    selected. Note that the HTTP::uri command does not include the
    hostname

   set static::Select_URI "/regist.asp?id=321&pid=123"
}
when HTTP_REQUEST {
   if { [HTTP::cookie exists $static::St_Cookie] }{
       The sticky cookie is here so the secondary pool should be used
      pool $static::Pool_Name
       Clean up the request before sending it to the server
      HTTP::cookie remove $static::St_Cookie
   }
   elseif {[ string tolower [HTTP::uri]] starts_with $static::Select_URI }{
      pool $static::Pool_Name
   }

}
when HTTP_RESPONSE {
   if { [LB::server pool] eq $static::Pool_Name }{
       Insert the sticky cookie, it has a value of 1, which is not used
       for anything since we're looking for the presence of the cookie
       and not the value
      HTTP::cookie insert name $static::St_Cookie value "1" path "/"
   }
}