I'm experimenting with the ruby filter to execute arbitrary ruby code on events and so far, its been very successful, but I have a couple of questions please.
 Is it possible to persist data between events? I appreciate that each log event is processed separately but wondered whether perhaps a variable could be 'global' and persist from event to event?
 Is it possible to call other ruby code from within that filter? For example would it be feasible to call an external ruby script and still have access to event['field'] type data?
Would be grateful for any pointers or resources which describe whats possible with this filter.