fluentd.conf

<source>   
  type   tail 
  path   /path/to/log.txt
  tag    tiarra.all
  format /^(?<time>[^ ]+\ [^ ]+)\ <(?<channel>[^ ]*):(?<nick>[^ ]*)>\ (?<log>.*)$/
  time_format  %Y/%m/%d %H:%M:%S
  pos_file /tmp/pos
</source>

tiarra.conf

+ Log::Channel {  
  directory: log
  charset: utf8  
  header: %Y/%m/%d %H:%M:%S                                                                           
  filename: log.txt                                                                                     
  mode: 600
  dir-mode: 700                                                                                       
  command: privmsg,topic,notice                                                                       
  distinguish-myself: 1                                                                                 
  sync: sync                                                                                          
  channel: log *                                                                                      
}