Try the latest logstash 1.2.1 and use codec value to parse json events directly.
input {
file {
type => "tweetfile"
path => ["/home/nikhil/temp/feed/*.txt"]
codec => "json"
}
}
filter{
json{
source => "message"
target => "tweet"
}
}
output {
stdout { }
elasticsearch { embedded => true }
}