配置logstash转发器时发现错误

Question

尝试在中央服务器上配置logstash转发器时，logstash.log中出现以下错误：

 {:timestamp=>"2015-07-07T09:05:14.742000-0500", :message=>"Unknown setting 'timestamp' for date", :level=>:error}
 {:timestamp=>"2015-07-07T09:05:14.744000-0500", :message=>"Error: Something is wrong with your configuration."}

有人可以帮忙解决这个问题吗？

以下是配置文件：/etc/logstash/conf.d/central.conf：

input {
    lumberjack {
        port => 6782
        ssl_certificate => "/etc/logstash/server.crt"
        ssl_key => "/etc/logstash/server.key"
        type => "lumberjack"
    }
}
output {
    stdout { }
    elasticsearch {
        cluster => "logstash"
    }
}