Simple HTTP::uri rule doesn't work as expected

FYI - this is caused be keepalive requests... If you don't explicitly select the pool, the last pool selection stands. Since multiple requests, may come on the same connection, it's a good idea to always have an else clause to pick the default pool.

Nope, you can grab the default pool and put it in a variable.

when CLIENT_ACCEPTED {
  set default_pool [LB::server pool]
}
when HTTP_REQUEST {
  if {...} {
     pool a
  }
  elseif {...} {
     pool b
  }
  else {
     pool $default_pool
  }
}