From 389dee0f3ca9340598d2760ab298681d22e1195d Mon Sep 17 00:00:00 2001
From: Bradley Cicenas <bradley@vektor.nyc>
Date: Sat, 10 Jun 2017 13:00:54 +0000
Subject: [PATCH] add percent helper method to metrics

---
 metrics/docker.go |  2 +-
 metrics/main.go   | 24 ++++++++++++++++--------
 metrics/mock.go   |  2 +-
 metrics/proc.go   |  1 +
 metrics/runc.go   |  2 +-
 5 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/metrics/docker.go b/metrics/docker.go
index 070ddcd..8f11b51 100644
--- a/metrics/docker.go
+++ b/metrics/docker.go
@@ -86,7 +86,7 @@ func (c *Docker) ReadCPU(stats *api.Stats) {
 func (c *Docker) ReadMem(stats *api.Stats) {
 	c.MemUsage = int64(stats.MemoryStats.Usage)
 	c.MemLimit = int64(stats.MemoryStats.Limit)
-	c.MemPercent = round((float64(c.MemUsage) / float64(c.MemLimit)) * 100)
+	c.MemPercent = percent(float64(c.MemUsage), float64(c.MemLimit))
 }
 
 func (c *Docker) ReadNet(stats *api.Stats) {
diff --git a/metrics/main.go b/metrics/main.go
index 387b01d..6ed90ba 100644
--- a/metrics/main.go
+++ b/metrics/main.go
@@ -22,14 +22,14 @@ type Metrics struct {
 
 func NewMetrics() Metrics {
 	return Metrics{
-		CPUUtil:           -1,
-		NetTx:             -1,
-		NetRx:             -1,
-		MemUsage:          -1,
-		MemPercent:        -1,
-		IOBytesRead:       -1,
-		IOBytesWrite:      -1,
-		Pids:              -1,
+		CPUUtil:      -1,
+		NetTx:        -1,
+		NetRx:        -1,
+		MemUsage:     -1,
+		MemPercent:   -1,
+		IOBytesRead:  -1,
+		IOBytesWrite: -1,
+		Pids:         -1,
 	}
 }
 
@@ -43,3 +43,11 @@ type Collector interface {
 func round(num float64) int {
 	return int(num + math.Copysign(0.5, num))
 }
+
+// return rounded percentage
+func percent(val float64, total float64) int {
+	if total <= 0 {
+		return 0
+	}
+	return round((val / total) * 100)
+}
diff --git a/metrics/mock.go b/metrics/mock.go
index deb3749..0cb47fd 100644
--- a/metrics/mock.go
+++ b/metrics/mock.go
@@ -60,7 +60,7 @@ func (c *Mock) run() {
 		if c.MemUsage > c.MemLimit {
 			c.MemUsage = 0
 		}
-		c.MemPercent = round((float64(c.MemUsage) / float64(c.MemLimit)) * 100)
+		c.MemPercent = percent(float64(c.MemUsage), float64(c.MemLimit))
 		c.stream <- c.Metrics
 		if c.done {
 			break
diff --git a/metrics/proc.go b/metrics/proc.go
index 5a0b81c..457585f 100644
--- a/metrics/proc.go
+++ b/metrics/proc.go
@@ -19,6 +19,7 @@ func getSysMemTotal() int64 {
 	return int64(stat.MemTotal * 1024)
 }
 
+// return cumulative system cpu usage in nanoseconds
 func getSysCPUUsage() uint64 {
 	stat, err := linuxproc.ReadStat("/proc/stat")
 	if err != nil {
diff --git a/metrics/runc.go b/metrics/runc.go
index 25420e7..44188bb 100644
--- a/metrics/runc.go
+++ b/metrics/runc.go
@@ -95,7 +95,7 @@ func (c *Runc) ReadMem(stats *cgroups.Stats) {
 	if c.MemLimit > sysMemTotal && sysMemTotal > 0 {
 		c.MemLimit = sysMemTotal
 	}
-	c.MemPercent = round((float64(c.MemUsage) / float64(c.MemLimit)) * 100)
+	c.MemPercent = percent(float64(c.MemUsage), float64(c.MemLimit))
 }
 
 func (c *Runc) ReadNet(interfaces []*libcontainer.NetworkInterface) {