StatsD

A network daemon that runs on the Node.js platform and listens for statistics, like counters and timers, sent over UDP or TCP and sends aggregates to one or more pluggable backend services (e.g., Graphite).

We (Etsy) blogged about how it works and why we created it.

Inspiration

StatsD was inspired (heavily) by the project (of the same name) at Flickr. Here's a post where Cal Henderson described it in depth: Counting and timing Cal re-released the code recently: Perl StatsD

Key Concepts

• buckets Each stat is in its own "bucket". They are not predefined anywhere. Buckets can be named anything that will translate to Graphite (periods make folders, etc)

• values Each stat will have a value. How it is interpreted depends on modifiers. In general values should be integer.

• flush After the flush interval timeout (defined by config.flushInterval, default 10 seconds), stats are aggregated and sent to an upstream backend service.

Installation and Configuration

• Install node.js
• Clone the project
• Create a config file from exampleConfig.js and put it somewhere
• Start the Daemon:
  node stats.js /path/to/config

Usage

The basic line protocol expects metrics to be sent in the format:

<metricname>:<value>|<type>

So the simplest way to send in metrics from your command line if you have StatsD running with the default UDP server on localhost would be:

echo "foo:1|c" | nc -u -w0 127.0.0.1 8125

More Specific Topics

• Metric Types
• Graphite Integration
• Supported Servers
• Supported Backends
• Admin TCP Interface
• Server Interface
• Backend Interface
• Metric Namespacing
• Statsd Cluster Proxy

Debugging

There are additional config variables available for debugging:

• debug - log exceptions and print out more diagnostic info
• dumpMessages - print debug info on incoming messages

For more information, check the exampleConfig.js.

Tests

A test framework has been added using node-unit and some custom code to start and manipulate statsd. Please add tests under test/ for any new features or bug fixes encountered. Testing a live server can be tricky, attempts were made to eliminate race conditions but it may be possible to encounter a stuck state. If doing dev work, a killall statsd will kill any stray test servers in the background (don't do this on a production machine!).

Tests can be executed with ./run_tests.sh.

Meta

• IRC channel: #statsd on freenode
• Mailing list: statsd@librelist.com