Metrics are numeric measurements over time. The most common types of metrics collected in our systems are counters, timers, and gauges. A counter is exactly what it sounds like, a value that is incremented a number of times over some time period. A timer can be used to measure recurring events in a system, such as the amount of time it takes to serve a request or perform a database query. Gauges are just arbitrary numeric values that can be recorded.
StatsD is an open source network daemon invented in 2011 at Etsy. Metrics data is pushed to a statsd server, often on the same server, which aggregates data before sending it on to a durable backend. One of the most common backends used with statsd is Graphite, an open source time-series storage engine and graphing tool. Together, Graphite and StatsD make up a very popular metrics stack...
