fix(util): check if err occurred when get CPU percent, to avoid panic if got nil result.

Signed-off-by: true1064 <tangjingyu@oppo.com>

datanode/server.go

@@ -865,8 +865,10 @@ func (s *DataNode) startCpuSample() {
 				return
 			default:
 				// this function will sleep cpuSampleDuration
-				used := loadutil.GetCpuUtilPercent(cpuSampleDuration)
-				s.cpuUtil.Store(used)
+				used, err := loadutil.GetCpuUtilPercent(cpuSampleDuration)
+				if err == nil {
+					s.cpuUtil.Store(used)
+				}
 			}
 		}
 	}()

metanode/manager.go

@@ -331,8 +331,10 @@ func (m *metadataManager) startCpuSample() {
 			case <-m.stopC:
 				return
 			default:
-				used := loadutil.GetCpuUtilPercent(sampleDuration)
-				m.cpuUtil.Store(used)
+				used, err := loadutil.GetCpuUtilPercent(sampleDuration)
+				if err == nil {
+					m.cpuUtil.Store(used)
+				}
 			}
 		}
 	}()

util/loadutil/cpu.go

@@ -15,12 +15,30 @@
 package loadutil
 
 import (
+	"fmt"
+	"github.com/cubefs/cubefs/util/log"
 	"time"
 
 	"github.com/shirou/gopsutil/cpu"
 )
 
-func GetCpuUtilPercent(sampleDuration time.Duration) float64 {
-	utils, _ := cpu.Percent(sampleDuration, false)
-	return utils[0]
+func GetCpuUtilPercent(sampleDuration time.Duration) (used float64, err error) {
+	utils, err := cpu.Percent(sampleDuration, false)
+	if err != nil {
+		log.LogErrorf("[GetCpuUtilPercent] err: %v", err.Error())
+		return
+	}
+	if utils == nil {
+		err = fmt.Errorf("got nil result")
+		log.LogErrorf("[GetCpuUtilPercent] err: %v", err.Error())
+		return
+	}
+	if len(utils) == 0 {
+		err = fmt.Errorf("got result len is 0")
+		log.LogErrorf("[GetCpuUtilPercent] err: %v", err.Error())
+		return
+	}
+
+	used = utils[0]
+	return
 }

util/loadutil/cpu_test.go

@@ -22,6 +22,6 @@ import (
 )
 
 func TestCpuUtil(t *testing.T) {
-	used := loadutil.GetCpuUtilPercent(time.Second)
+	used, _ := loadutil.GetCpuUtilPercent(time.Second)
 	t.Logf("CPU Util: %v\n", used)
 }