refactor statreader into metricreader, add processed metrics stream

reader.go

@@ -6,47 +6,65 @@ import (
 	"github.com/fsouza/go-dockerclient"
 )
 
-type StatReader struct {
+type Metrics struct {
 	CPUUtil    int
 	NetTx      int64
 	NetRx      int64
 	MemLimit   int64
 	MemPercent int
 	MemUsage   int64
+}
+
+type MetricsReader struct {
+	Metrics
 	lastCpu    float64
 	lastSysCpu float64
 }
 
-func (s *StatReader) Read(stats *docker.Stats) {
-	s.ReadCPU(stats)
-	s.ReadMem(stats)
-	s.ReadNet(stats)
+func NewMetricsReader() *MetricsReader {
+	return &MetricsReader{}
 }
 
-func (s *StatReader) ReadCPU(stats *docker.Stats) {
+func (m *MetricsReader) Read(statsCh chan *docker.Stats) chan Metrics {
+	stream := make(chan Metrics)
+
+	go func() {
+		for s := range statsCh {
+			m.ReadCPU(s)
+			m.ReadMem(s)
+			m.ReadNet(s)
+			stream <- m.Metrics
+		}
+	}()
+
+	return stream
+}
+
+func (m *MetricsReader) ReadCPU(stats *docker.Stats) {
 	ncpus := float64(len(stats.CPUStats.CPUUsage.PercpuUsage))
 	total := float64(stats.CPUStats.CPUUsage.TotalUsage)
 	system := float64(stats.CPUStats.SystemCPUUsage)
 
-	cpudiff := total - s.lastCpu
-	syscpudiff := system - s.lastSysCpu
-	s.CPUUtil = round((cpudiff / syscpudiff * 100) * ncpus)
-	s.lastCpu = total
-	s.lastSysCpu = system
+	cpudiff := total - m.lastCpu
+	syscpudiff := system - m.lastSysCpu
+	m.CPUUtil = round((cpudiff / syscpudiff * 100) * ncpus)
+	m.lastCpu = total
+	m.lastSysCpu = system
 }
 
-func (s *StatReader) ReadMem(stats *docker.Stats) {
-	s.MemUsage = int64(stats.MemoryStats.Usage)
-	s.MemLimit = int64(stats.MemoryStats.Limit)
-	s.MemPercent = round((float64(s.MemUsage) / float64(s.MemLimit)) * 100)
+func (m *MetricsReader) ReadMem(stats *docker.Stats) {
+	m.MemUsage = int64(stats.MemoryStats.Usage)
+	m.MemLimit = int64(stats.MemoryStats.Limit)
+	m.MemPercent = round((float64(m.MemUsage) / float64(m.MemLimit)) * 100)
 }
 
-func (s *StatReader) ReadNet(stats *docker.Stats) {
-	s.NetTx, s.NetRx = 0, 0
+func (m *MetricsReader) ReadNet(stats *docker.Stats) {
+	var rx, tx int64
 	for _, network := range stats.Networks {
-		s.NetTx += int64(network.TxBytes)
-		s.NetRx += int64(network.RxBytes)
+		rx += int64(network.RxBytes)
+		tx += int64(network.TxBytes)
 	}
+	m.NetRx, m.NetTx = rx, tx
 }
 
 func round(num float64) int {