lib/metrics.js
function Counter(key, tags, host) {
    Metric.call(this, key, tags, host);
    this.value = 0;
}
function Counter(key, tags, host) {
    Metric.call(this, key, tags, host);
    this.value = 0;
}
COUNTER ------- Increment the counter by the given *value*. Optionally, specify a list of *tags* to associate with the metric. This is useful for counting things such as incrementing a counter each time a page is requested.