At my company we've been using Graphite and StatsD for nearly two years now, we rely on it heavily for tracking performance and troubleshooting issues. We rely on Icinga, Pingdom, NewRelic and other tools to alert of us of problems.<p>Often, when things have gone really wrong (DoS, internal network issues, app errors, disk full) the affected machine(s) stop reporting to graphite (or under-report data). We get alerted by monitoring the services, not the stats.<p>Being alerted about low or unusual values might be helpful in some cases, but based on my experience, it would too noisy. Usually when something bad happens, we anyway investigate Graphite and analytics tools to understand the impact on traffic and KPIs.<p>I could see Rearview being useful for some cases, but not as a replacement for real monitoring and alerting tools.