Revert "use the external library to collect CPU usage on darwin"

This reverts commit cf53f71.

command/command_darwin.go

@@ -24,7 +24,7 @@ func interfaceGenerator() spec.InterfaceGenerator {
 func metricsGenerators(conf *config.Config) []metrics.Generator {
 	generators := []metrics.Generator{
 		&metricsDarwin.Loadavg5Generator{},
-		&metricsDarwin.CPUUsageGenerator{Interval: metricsInterval},
+		&metricsDarwin.CPUUsageGenerator{},
 		&metricsDarwin.MemoryGenerator{},
 		&metrics.FilesystemGenerator{IgnoreRegexp: conf.Filesystems.Ignore.Regexp, UseMountpoint: conf.Filesystems.UseMountpoint},
 		&metricsDarwin.InterfaceGenerator{Interval: metricsInterval},

metrics/darwin/cpuusage.go

@@ -3,51 +3,62 @@
 package darwin
 
 import (
-	"errors"
-	"time"
+	"fmt"
+	"os/exec"
+	"strconv"
+	"strings"
 
-	"github.com/mackerelio/go-osstat/cpu"
 	"github.com/mackerelio/golib/logging"
 	"github.com/mackerelio/mackerel-agent/metrics"
 )
 
 // CPUUsageGenerator XXX
 type CPUUsageGenerator struct {
-	Interval time.Duration
 }
 
 var cpuUsageLogger = logging.GetLogger("metrics.cpuUsage")
 
+var iostatFieldToMetricName = []string{"user", "system", "idle"}
+
 // Generate returns current CPU usage of the host.
 // Keys below are expected:
 // - cpu.user.percentage
 // - cpu.system.percentage
 // - cpu.idle.percentage
 func (g *CPUUsageGenerator) Generate() (metrics.Values, error) {
-	before, err := cpu.Get()
+
+	// $ iostat -n0 -c2
+	//         cpu     load average
+	//    us sy id   1m   5m   15m
+	//    13  7 81  1.93 2.23 2.65
+	//    13  7 81  1.93 2.23 2.65
+	iostatBytes, err := exec.Command("iostat", "-n0", "-c2").Output()
 	if err != nil {
-		cpuUsageLogger.Errorf("failed to get cpu statistics: %s", err)
+		cpuUsageLogger.Errorf("Failed to invoke iostat: %s", err)
 		return nil, err
 	}
 
-	time.Sleep(g.Interval)
+	iostat := string(iostatBytes)
+	lines := strings.Split(iostat, "\n")
+	if len(lines) != 5 {
+		return nil, fmt.Errorf("iostat result malformed: [%q]", iostat)
+	}
 
-	after, err := cpu.Get()
-	if err != nil {
-		cpuUsageLogger.Errorf("failed to get cpu statistics: %s", err)
-		return nil, err
+	fields := strings.Fields(lines[3])
+	if len(fields) < len(iostatFieldToMetricName) {
+		return nil, fmt.Errorf("iostat result malformed: [%q]", iostat)
 	}
 
-	if before.Total == after.Total {
-		err := errors.New("cpu total counter did not change")
-		cpuUsageLogger.Errorf("%s", err)
-		return nil, err
+	cpuUsage := make(map[string]float64, len(iostatFieldToMetricName))
+
+	for i, n := range iostatFieldToMetricName {
+		value, err := strconv.ParseFloat(fields[i], 64)
+		if err != nil {
+			return nil, err
+		}
+
+		cpuUsage["cpu."+n+".percentage"] = value
 	}
 
-	cpuUsage := make(map[string]float64, 3)
-	total := float64(after.Total - before.Total)
-	cpuUsage["cpu.user.percentage"] = float64(after.User-before.User) / total * 100.0
-	cpuUsage["cpu.system.percentage"] = float64(after.System-before.System) / total * 100.0
-	cpuUsage["cpu.idle.percentage"] = float64(after.Idle-before.Idle) / total * 100.0
 	return metrics.Values(cpuUsage), nil
 }

metrics/darwin/cpuusage_test.go

@@ -2,26 +2,20 @@
 
 package darwin
 
-import (
-	"testing"
-	"time"
-)
+import "testing"
 
 func TestCPUUsageGenerator_Generate(t *testing.T) {
-	g := &CPUUsageGenerator{1 * time.Second}
+	g := &CPUUsageGenerator{}
 	values, err := g.Generate()
 
 	if err != nil {
 		t.Errorf("error should not have occurred: %s", err)
 	}
 
-	metricNames := []string{"cpu.user.percentage", "cpu.system.percentage", "cpu.idle.percentage"}
-
-	for _, name := range metricNames {
-		if v, ok := values[name]; !ok {
-			t.Errorf("cpu should has %s", name)
-		} else {
-			t.Logf("cpu '%s' collected: %+v", name, v)
+	metricName := []string{"cpu.user.percentage", "cpu.system.percentage", "cpu.idle.percentage"}
+	for _, n := range metricName {
+		if _, ok := values[n]; !ok {
+			t.Errorf("should have '%s': %v", n, values)
 		}
 	}
 }