Simple hardware metrics collection + alerting (#115)

* Add CPU and RAM usage alerting

* Create basic troubleshooting document to point alerts at

* Limit max number of hardware values collected

* Save metric value with the point in time it was taken

metrics/metrics.go

@@ -0,0 +1,39 @@
+package metrics
+
+import (
+	"time"
+)
+
+// How often we poll for updates
+const metricsPollingInterval = 15 * time.Second
+
+type value struct {
+	Time  time.Time
+	Value int
+}
+
+type metrics struct {
+	CPUUtilizations []value
+	RAMUtilizations []value
+}
+
+// Metrics is the shared Metrics instance
+var Metrics *metrics
+
+// Start will begin the metrics collection and alerting
+func Start() {
+	Metrics = new(metrics)
+
+	for range time.Tick(metricsPollingInterval) {
+		handlePolling()
+	}
+}
+
+func handlePolling() {
+	// Collect hardware stats
+	collectCPUUtilization()
+	collectRAMUtilization()
+
+	// Alerting
+	handleAlerting()
+}