iRule | route to another pool according to URI

Set a cookie for the client that specifies the current branchcode.

Use the cookie value to determine what pool the client request is sent to.

When they make a request that changes the branchcode, change the cookie value to the new branchcode.

You could use the client IP and a subtable, but for HTTP a cookie is the appropriate mechanism for maintaining state.

Here is some example code - it works as expected, but you should check it out and adjust it to your requirements.

when HTTP_REQUEST {
  set new_branchcode ""
  log local0. "branchcode is [URI::query [string tolower [HTTP::uri]] "branchcode"]"
  switch [URI::query [string tolower [HTTP::uri]] "branchcode"] {
    123 {
       HTTP::cookie remove "branchcode"
       HTTP::cookie insert name "branchcode" value "123"
       log local0. "updating branchcode cookie to 123"
       set new_branchcode "123"
    }
    456 {
       HTTP::cookie remove "branchcode"
       HTTP::cookie insert name "branchcode" value "456"
       log local0. "updating branchcode cookie to 456"
       set new_branchcode "456"
    }
  }
 
  log local0. "selecting the pool based on branchcode cookie [HTTP::cookie value {branchcode}]"
  
  switch [HTTP::cookie value {branchcode}] {
    123 {
      # pool 123_pool
      log local0. "pool is 123_pool"
    }
    456 {
      # pool 456_pool
      log local0. "pool is 456_pool"
    }
    default {
      # select default pool
      log local0. "pool is default pool"
    }
  }
}
 
when HTTP_RESPONSE {
  if {![string equal $new_branchcode ""]} {
    log local0. "sending a new cookie $new_branchcode"
    HTTP::cookie insert name "branchcode" value $new_branchcode
  }
}