Ask HN: Open Source Metrics Collection System

Hi HN,

I'm looking for self hosted (open-source) alternative to Stathat[0]. Basically, we want to send custom events to be captured and plotted with the ability to set alerts on these metrics. I do understand that this is something a lot of companies have built in house but if there are good open-source alternatives we could avoid a custom solution.

[0] - http://stathat.com

Thanks!