out_forward.conf

<source>
  @type sample
  tag test
</source>

<match test>
  @type forward

  <server>
    # first server
    host 127.0.0.1
    port 24224
  </server>
  # <server>
  #   # second server
  #   host localhost
  #   port 24225
  # </server>
  # <server>
  #   # second server
  #   host localhost
  #   port 24226
  #   standby
  # </server>

  flush_interval 0
  send_timeout 60
  heartbeat_type udp
  heartbeat_interval 1
  recover_wait 10
  hard_timeout 60
  expire_dns_cache nil
  phi_threshold 16
  phi_failure_detector true
</match>