Initial spike

This is mostly to solidify the overall structure with the agent,
plugins, and testing philosphy.

plugins/system/system.go

@@ -0,0 +1,64 @@
+package system
+
+import (
+	"github.com/influxdb/tivan/plugins"
+	"github.com/shirou/gopsutil/load"
+	"github.com/vektra/cypress"
+)
+
+type PS interface {
+	LoadAvg() (*load.LoadAvgStat, error)
+}
+
+type SystemStats struct {
+	ps   PS
+	tags map[string]string
+}
+
+func (s *SystemStats) Read() ([]*cypress.Message, error) {
+	lv, err := s.ps.LoadAvg()
+	if err != nil {
+		return nil, err
+	}
+
+	m1 := cypress.Metric()
+	m1.Add("type", "gauge")
+	m1.Add("name", "load1")
+	m1.Add("value", lv.Load1)
+
+	for k, v := range s.tags {
+		m1.AddTag(k, v)
+	}
+
+	m2 := cypress.Metric()
+	m2.Add("type", "gauge")
+	m2.Add("name", "load5")
+	m2.Add("value", lv.Load5)
+
+	for k, v := range s.tags {
+		m2.AddTag(k, v)
+	}
+
+	m3 := cypress.Metric()
+	m3.Add("type", "gauge")
+	m3.Add("name", "load15")
+	m3.Add("value", lv.Load15)
+
+	for k, v := range s.tags {
+		m3.AddTag(k, v)
+	}
+
+	return []*cypress.Message{m1, m2, m3}, nil
+}
+
+type systemPS struct{}
+
+func (s *systemPS) LoadAvg() (*load.LoadAvgStat, error) {
+	return load.LoadAvg()
+}
+
+func init() {
+	plugins.Add("system", func() plugins.Plugin {
+		return &SystemStats{ps: &systemPS{}}
+	})
+}