Tracking how much logstash has read from a file or How much is its backlog


I get a set of zipped log files from an external application. I have a process that would unzip the files so that logstash can forward them to elastic search. Just wanted help to know if there is anyway I can figure out if logstash has completed forwarding the file to elasticsearch so that they can be removed as well as I can distribute the load to forwards who have completed.