StatsD Proxying

[patricksanders]

Description

Add the ability to send statsd on to another address, essentially acting as a proxy that provides visibility of what's going through it.

Considerations

This feature could lead to a lack of awareness of statsdebug since it would be passively collecting metric metrics. Since data is stored in memory, resource usage could become an issue for a long-running statsdebug instance that receives a lot of traffic. Potential workarounds include automatic aging out of data, on-demand enabling of data gathering, or maybe just communicating that users should be mindful of memory usage (I like this one).

[cranti]

I think the last option sounds fine. A few ideas to make that practical:

• Add an endpoint that toggles whether data is collected, so that it can run quietly without causing problems. The "reset" endpoint also helps.
• Allow users to set a memory limit for collected metrics, so that it continues to pass metrics without storing them, if it's at risk of OOMing

Is it worth setting up a storage interface, so that it could (someday) be a pluggable option?