don't truncate output file each time we open it
don't truncate output file each time we open it

opentable/logstash-kafka,tinglinux/logstash-kafka,Aloomaio/logstash-kafka,joekiller/logstash-kafka,joekiller/logstash-kafka,tinglinux/logstash-kafka,opentable/logstash-kafka,Aloomaio/logstash-kafka