<source>
  @type dummy
  @label @dummylog
  tag "data"
  dummy {"message":"yay"}
</source>
<label @dummylog>
  <match **>
    @type stdout
  </match>
</label>
<label @FLUENT_LOG>
  <match fluent.debug fluent.info fluent.warn fluent.error fluent.fatal>
    @type stdout
    <inject>
      hostname_key "host"
    </inject>
  </match>
  # <match fluent.{info,warn,error,fatal}>
  #   @type stdout
  #   <inject>
  #     hostname_key "host"
  #   </inject>
  # </match>
</label> 