GAUGE ----- Record the current *value* of a metric. They most recent value in a given flush interval will be recorded. Optionally, specify a set of tags to associate with the metric. This should be used for sum values such as total hard disk space, process uptime, total number of active users, or number of rows in a database table.
function Gauge(key, tags, host) {
    Metric.call(this, key, tags, host);
    this.value = 0;
}