Fix invalid CPU stats on Windows

This PR fixes an issue introduced in Nomad 0.6.0 due to
shirou/gopsutil#420. The issue arised from the
fact that the Windows stats from gopsutil reports CPUs in
percentages where we expected ticks.

client/stats/cpu_test.go

@@ -1,8 +1,14 @@
 package stats
 
 import (
+	"log"
+	"math"
+	"os"
 	"testing"
 	"time"
+
+	shelpers "github.com/hashicorp/nomad/helper/stats"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestCpuStatsPercent(t *testing.T) {
@@ -15,3 +21,39 @@ func TestCpuStatsPercent(t *testing.T) {
 		t.Fatalf("expected: %v, actual: %v", expectedPercent, percent)
 	}
 }
+
+func TestHostStats_CPU(t *testing.T) {
+	assert := assert.New(t)
+	assert.Nil(shelpers.Init())
+
+	logger := log.New(os.Stderr, "", log.LstdFlags|log.Lmicroseconds)
+	cwd, err := os.Getwd()
+	assert.Nil(err)
+	hs := NewHostStatsCollector(logger, cwd)
+
+	// Collect twice so we can calculate percents we need to generate some work
+	// so that the cpu values change
+	assert.Nil(hs.Collect())
+	total := 0
+	for i := 1; i < 1000000000; i++ {
+		total *= i
+		total = total % i
+	}
+	assert.Nil(hs.Collect())
+	stats := hs.Stats()
+
+	assert.NotZero(stats.CPUTicksConsumed)
+	assert.NotZero(len(stats.CPU))
+
+	for _, cpu := range stats.CPU {
+		assert.False(math.IsNaN(cpu.Idle))
+		assert.False(math.IsNaN(cpu.Total))
+		assert.False(math.IsNaN(cpu.System))
+		assert.False(math.IsNaN(cpu.User))
+
+		assert.False(math.IsInf(cpu.Idle, 0))
+		assert.False(math.IsInf(cpu.Total, 0))
+		assert.False(math.IsInf(cpu.System, 0))
+		assert.False(math.IsInf(cpu.User, 0))
+	}
+}

client/stats/cpu_unix.go

@@ -0,0 +1,36 @@
+// +build !windows
+
+package stats
+
+import (
+	shelpers "github.com/hashicorp/nomad/helper/stats"
+	"github.com/shirou/gopsutil/cpu"
+)
+
+func (h *HostStatsCollector) collectCPUStats() (cpus []*CPUStats, totalTicks float64, err error) {
+
+	ticksConsumed := 0.0
+	cpuStats, err := cpu.Times(true)
+	if err != nil {
+		return nil, 0.0, err
+	}
+	cs := make([]*CPUStats, len(cpuStats))
+	for idx, cpuStat := range cpuStats {
+		percentCalculator, ok := h.statsCalculator[cpuStat.CPU]
+		if !ok {
+			percentCalculator = NewHostCpuStatsCalculator()
+			h.statsCalculator[cpuStat.CPU] = percentCalculator
+		}
+		idle, user, system, total := percentCalculator.Calculate(cpuStat)
+		cs[idx] = &CPUStats{
+			CPU:    cpuStat.CPU,
+			User:   user,
+			System: system,
+			Idle:   idle,
+			Total:  total,
+		}
+		ticksConsumed += (total / 100.0) * (shelpers.TotalTicksAvailable() / float64(len(cpuStats)))
+	}
+
+	return cs, ticksConsumed, nil
+}

client/stats/cpu_windows.go

@@ -0,0 +1,53 @@
+// +build windows
+
+package stats
+
+import (
+	"fmt"
+
+	shelpers "github.com/hashicorp/nomad/helper/stats"
+	"github.com/shirou/gopsutil/cpu"
+)
+
+func (h *HostStatsCollector) collectCPUStats() (cpus []*CPUStats, totalTicks float64, err error) {
+	// Get the per cpu stats
+	cpuStats, err := cpu.Times(true)
+	if err != nil {
+		return nil, 0.0, err
+	}
+
+	cs := make([]*CPUStats, len(cpuStats))
+	for idx, cpuStat := range cpuStats {
+
+		// On windows they are already in percent
+		cs[idx] = &CPUStats{
+			CPU:    cpuStat.CPU,
+			User:   cpuStat.User,
+			System: cpuStat.System,
+			Idle:   cpuStat.Idle,
+			Total:  cpuStat.Total(),
+		}
+	}
+
+	// Get the number of ticks
+	allCpu, err := cpu.Times(false)
+	if err != nil {
+		return nil, 0.0, err
+	}
+	if len(allCpu) != 1 {
+		return nil, 0.0, fmt.Errorf("unexpected number of cpus (%d)", len(allCpu))
+	}
+
+	// We use the calculator because when retrieving against all cpus it is
+	// returned as ticks.
+	all := allCpu[0]
+	percentCalculator, ok := h.statsCalculator[all.CPU]
+	if !ok {
+		percentCalculator = NewHostCpuStatsCalculator()
+		h.statsCalculator[all.CPU] = percentCalculator
+	}
+	_, _, _, total := percentCalculator.Calculate(all)
+	ticks := (total / 100) * shelpers.TotalTicksAvailable()
+
+	return cs, ticks, nil
+}

client/stats/host.go

@@ -11,8 +11,6 @@ import (
 	"github.com/shirou/gopsutil/disk"
 	"github.com/shirou/gopsutil/host"
 	"github.com/shirou/gopsutil/mem"
-
-	shelpers "github.com/hashicorp/nomad/helper/stats"
 )
 
 // HostStats represents resource usage stats of the host running a Nomad client
@@ -95,46 +93,72 @@ func NewHostStatsCollector(logger *log.Logger, allocDir string) *HostStatsCollec
 // Collect collects stats related to resource usage of a host
 func (h *HostStatsCollector) Collect() error {
 	hs := &HostStats{Timestamp: time.Now().UTC().UnixNano()}
-	memStats, err := mem.VirtualMemory()
+
+	// Determine up-time
+	uptime, err := host.Uptime()
 	if err != nil {
 		return err
 	}
-	hs.Memory = &MemoryStats{
-		Total:     memStats.Total,
-		Available: memStats.Available,
-		Used:      memStats.Used,
-		Free:      memStats.Free,
+	hs.Uptime = uptime
+
+	// Collect memory stats
+	mstats, err := h.collectMemoryStats()
+	if err != nil {
+		return err
 	}
+	hs.Memory = mstats
 
-	ticksConsumed := 0.0
-	cpuStats, err := cpu.Times(true)
+	// Collect cpu stats
+	cpus, ticks, err := h.collectCPUStats()
 	if err != nil {
 		return err
 	}
-	cs := make([]*CPUStats, len(cpuStats))
-	for idx, cpuStat := range cpuStats {
-		percentCalculator, ok := h.statsCalculator[cpuStat.CPU]
-		if !ok {
-			percentCalculator = NewHostCpuStatsCalculator()
-			h.statsCalculator[cpuStat.CPU] = percentCalculator
-		}
-		idle, user, system, total := percentCalculator.Calculate(cpuStat)
-		cs[idx] = &CPUStats{
-			CPU:    cpuStat.CPU,
-			User:   user,
-			System: system,
-			Idle:   idle,
-			Total:  total,
-		}
-		ticksConsumed += (total / 100) * (shelpers.TotalTicksAvailable() / float64(len(cpuStats)))
+	hs.CPU = cpus
+	hs.CPUTicksConsumed = ticks
+
+	// Collect disk stats
+	diskStats, err := h.collectDiskStats()
+	if err != nil {
+		return err
 	}
-	hs.CPU = cs
-	hs.CPUTicksConsumed = ticksConsumed
+	hs.DiskStats = diskStats
 
-	partitions, err := disk.Partitions(false)
+	// Getting the disk stats for the allocation directory
+	usage, err := disk.Usage(h.allocDir)
 	if err != nil {
 		return err
 	}
+	hs.AllocDirStats = h.toDiskStats(usage, nil)
+
+	// Update the collected status object.
+	h.hostStatsLock.Lock()
+	h.hostStats = hs
+	h.hostStatsLock.Unlock()
+
+	return nil
+}
+
+func (h *HostStatsCollector) collectMemoryStats() (*MemoryStats, error) {
+	memStats, err := mem.VirtualMemory()
+	if err != nil {
+		return nil, err
+	}
+	mem := &MemoryStats{
+		Total:     memStats.Total,
+		Available: memStats.Available,
+		Used:      memStats.Used,
+		Free:      memStats.Free,
+	}
+
+	return mem, nil
+}
+
+func (h *HostStatsCollector) collectDiskStats() ([]*DiskStats, error) {
+	partitions, err := disk.Partitions(false)
+	if err != nil {
+		return nil, err
+	}
+
 	var diskStats []*DiskStats
 	for _, partition := range partitions {
 		usage, err := disk.Usage(partition.Mountpoint)
@@ -153,25 +177,8 @@ func (h *HostStatsCollector) Collect() error {
 		ds := h.toDiskStats(usage, &partition)
 		diskStats = append(diskStats, ds)
 	}
-	hs.DiskStats = diskStats
-
-	// Getting the disk stats for the allocation directory
-	usage, err := disk.Usage(h.allocDir)
-	if err != nil {
-		return err
-	}
-	hs.AllocDirStats = h.toDiskStats(usage, nil)
-
-	uptime, err := host.Uptime()
-	if err != nil {
-		return err
-	}
-	hs.Uptime = uptime
 
-	h.hostStatsLock.Lock()
-	h.hostStats = hs
-	h.hostStatsLock.Unlock()
-	return nil
+	return diskStats, nil
 }
 
 // Stats returns the host stats that has been collected
@@ -228,28 +235,26 @@ func (h *HostCpuStatsCalculator) Calculate(times cpu.TimesStat) (idle float64, u
 	currentUser := times.User
 	currentSystem := times.System
 	currentTotal := times.Total()
+	currentBusy := times.User + times.System + times.Nice + times.Iowait + times.Irq +
+		times.Softirq + times.Steal + times.Guest + times.GuestNice + times.Stolen
 
 	deltaTotal := currentTotal - h.prevTotal
 	idle = ((currentIdle - h.prevIdle) / deltaTotal) * 100
-	if math.IsNaN(idle) {
+	user = ((currentUser - h.prevUser) / deltaTotal) * 100
+	system = ((currentSystem - h.prevSystem) / deltaTotal) * 100
+	total = ((currentBusy - h.prevBusy) / deltaTotal) * 100
+
+	// Protect against any invalid values
+	if math.IsNaN(idle) || math.IsInf(idle, 0) {
 		idle = 100.0
 	}
-
-	user = ((currentUser - h.prevUser) / deltaTotal) * 100
-	if math.IsNaN(user) {
+	if math.IsNaN(user) || math.IsInf(user, 0) {
 		user = 0.0
 	}
-
-	system = ((currentSystem - h.prevSystem) / deltaTotal) * 100
-	if math.IsNaN(system) {
+	if math.IsNaN(system) || math.IsInf(system, 0) {
 		system = 0.0
 	}
-
-	currentBusy := times.User + times.System + times.Nice + times.Iowait + times.Irq +
-		times.Softirq + times.Steal + times.Guest + times.GuestNice + times.Stolen
-
-	total = ((currentBusy - h.prevBusy) / deltaTotal) * 100
-	if math.IsNaN(total) {
+	if math.IsNaN(total) || math.IsInf(total, 0) {
 		total = 0.0
 	}
 
@@ -258,6 +263,5 @@ func (h *HostCpuStatsCalculator) Calculate(times cpu.TimesStat) (idle float64, u
 	h.prevSystem = currentSystem
 	h.prevTotal = currentTotal
 	h.prevBusy = currentBusy
-
 	return
 }