Sincedb, file input plugin used in multiple Logstash process


I am using logstash 1.5.4. and logstash file input plugin to poll data from files. If I use multiple instance of logstash, portfile1.conf file is like this:
input { file { path => "/…/access_log2" sincedb_path => "/tmp/sincedb1/s2" } }
portfile2.conf file is this
input { file { path => "/…/access_log1" sincedb_path => "/tmp/sincedb1/s1" } }

they cannot import data at the same time. One must finish before another one starts

But if I set one portfile1.conf file sincedb_path => "/dev/null", then they can import data at the same time. Sincedb is for keeping track of the offset, so in my program, I really need it.

How can I use multiple logstash instances to import data from files at the same time, and still use sincedb to keep track of their offset.

(system) #2