Why use statsd when graphite’s Carbon aggregator can do the same job?

StatsD operates over UDP, which removes the risk of carbon-aggregator.py being slow to respond and introducing latency in your application. In other words, loose coupling.

StatsD supports sampling of inbound metrics, which is useful when you don’t want your aggregator to take 100% of all data points to compute descriptive statistics. For high-volume code sections, it is common to use 0.5%-1% sample rates so as to not overload StatsD.

StatsD has broad client-side support.