# mappers/statsd

The statsd mapper transforms beacon data into [statsd][statsd] [timers][timers]. It accepts one option, `prefix` (`-x` from the command line), which allows you to specify a namespace that will be applied to the beginning of mapped timer names. This mapper also exports a separator string, `'\n'`, for use by forwarders in the event that they need to chunk data into packets before sending.

Currently, this mapper will only translate data from the `rt`, `navtiming` and `restiming` boomerang plugins.

Data from the round trip plugin is mapped as follows:

```
<prefix>.rt.firstbyte:<time>|ms
<prefix>.rt.lastbyte:<time>|ms
<prefix>.rt.load:<time>|ms
```

Data from the navigation timing plugin is mapped like so:

```
<prefix>.navtiming.unload:<time>|ms
<prefix>.navtiming.redirect:<time>|ms
<prefix>.navtiming.dns:<time>|ms
<prefix>.navtiming.connect:<time>|ms
<prefix>.navtiming.response:<time>|ms
<prefix>.navtiming.dom:<time>|ms
<prefix>.navtiming.domContent:<time>|ms
<prefix>.navtiming.load:<time>|ms
```

The mapping of resource timing data is currently somewhat experimental and liable to change in future versions. It features a base-36 encoding of page and resource URLs, to make them compatible with statsd namespaces. The mapped data looks like this:

```
<prefix>.restiming.<encoded page url>.<resource index>.<initiator type>.<encoded resource url>.redirect:<time>|ms
<prefix>.restiming.<encoded page url>.<resource index>.<initiator type>.<encoded resource url>.dns:<time>|ms
<prefix>.restiming.<encoded page url>.<resource index>.<initiator type>.<encoded resource url>.connect:<time>|ms
<prefix>.restiming.<encoded page url>.<resource index>.<initiator type>.<encoded resource url>.response:<time>|ms
```

Here is a reference implementation of a function for decoding the base-36 encoded URLs:

```javascript
function decodeBase36 (encoded, decoded) {
	if (!decoded) {
		decoded = '';
	}

	if (encoded === '') {
		return decoded;
	}

	return decodeBase36(encoded.substr(2), decoded + String.fromCharCode(parseInt(encoded.substr(0, 2), 36)));
}
```

It should be called with one argument, the base-36 encoded string.

[statsd]: https://github.com/etsy/statsd
[timers]: https://github.com/etsy/statsd/blob/master/docs/metric_types.md#timing