[receiver/hostmetrics] Fix calculation of process.cpu.utilization (#…

…19166)

Fixes the calculation of process CPU utilization. Rather than using a single ucal.CPUUtilizationCalculator struct to calculate the utilization over the collection interval, maintain one for each PID. After each scrape, remove any entries for PIDs that are no longer present.

.chloggen/fix_hostmetricsreceiver-processutilization.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: hostmetricsreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix `process.cpu.utilization` calculation by using individual `CPUUtilizationCalculator` instances per-PID.
+
+# One or more tracking issues related to the change
+issues: [19119]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: Update `processscraper` to keep a map of PIDs to `CPUUtilizationCalculator`s, rather than using a single instance globally.

receiver/hostmetricsreceiver/internal/scraper/processscraper/factory_test.go

@@ -35,7 +35,7 @@ func TestCreateResourceMetricsScraper(t *testing.T) {
 
 	scraper, err := factory.CreateMetricsScraper(context.Background(), receivertest.NewNopCreateSettings(), cfg)
 
-	if runtime.GOOS == "linux" || runtime.GOOS == "windows" {
+	if runtime.GOOS == "linux" || runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
 		assert.NoError(t, err)
 		assert.NotNil(t, scraper)
 	} else {

receiver/hostmetricsreceiver/internal/scraper/processscraper/process_scraper.go

@@ -55,7 +55,7 @@ type scraper struct {
 	includeFS          filterset.FilterSet
 	excludeFS          filterset.FilterSet
 	scrapeProcessDelay time.Duration
-	ucal               *ucal.CPUUtilizationCalculator
+	ucals              map[int32]*ucal.CPUUtilizationCalculator
 	// for mocking
 	getProcessCreateTime func(p processHandle) (int64, error)
 	getProcessHandles    func() (processHandles, error)
@@ -69,7 +69,7 @@ func newProcessScraper(settings receiver.CreateSettings, cfg *Config) (*scraper,
 		getProcessCreateTime: processHandle.CreateTime,
 		getProcessHandles:    getProcessHandlesInternal,
 		scrapeProcessDelay:   cfg.ScrapeProcessDelay,
-		ucal:                 &ucal.CPUUtilizationCalculator{},
+		ucals:                make(map[int32]*ucal.CPUUtilizationCalculator),
 	}
 
 	var err error
@@ -109,10 +109,14 @@ func (s *scraper) scrape(_ context.Context) (pmetric.Metrics, error) {
 		errs.AddPartial(partialErr.Failed, partialErr)
 	}
 
+	presentPIDs := make(map[int32]struct{}, len(data))
+
 	for _, md := range data {
+		presentPIDs[md.pid] = struct{}{}
+
 		now := pcommon.NewTimestampFromTime(time.Now())
 
-		if err = s.scrapeAndAppendCPUTimeMetric(now, md.handle); err != nil {
+		if err = s.scrapeAndAppendCPUTimeMetric(now, md.handle, md.pid); err != nil {
 			errs.AddPartial(cpuMetricsLen, fmt.Errorf("error reading cpu times for process %q (pid %v): %w", md.executable.name, md.pid, err))
 		}
 
@@ -152,6 +156,13 @@ func (s *scraper) scrape(_ context.Context) (pmetric.Metrics, error) {
 		s.mb.EmitForResource(options...)
 	}
 
+	// Cleanup any [ucal.CPUUtilizationCalculator]s for PIDs that are no longer present
+	for pid := range s.ucals {
+		if _, ok := presentPIDs[pid]; !ok {
+			delete(s.ucals, pid)
+		}
+	}
+
 	return s.mb.Emit(), errs.Combine()
 }
 
@@ -227,7 +238,7 @@ func (s *scraper) getProcessMetadata() ([]*processMetadata, error) {
 	return data, errs.Combine()
 }
 
-func (s *scraper) scrapeAndAppendCPUTimeMetric(now pcommon.Timestamp, handle processHandle) error {
+func (s *scraper) scrapeAndAppendCPUTimeMetric(now pcommon.Timestamp, handle processHandle, pid int32) error {
 	if !s.config.MetricsBuilderConfig.Metrics.ProcessCPUTime.Enabled {
 		return nil
 	}
@@ -238,8 +249,11 @@ func (s *scraper) scrapeAndAppendCPUTimeMetric(now pcommon.Timestamp, handle pro
 	}
 
 	s.recordCPUTimeMetric(now, times)
+	if _, ok := s.ucals[pid]; !ok {
+		s.ucals[pid] = &ucal.CPUUtilizationCalculator{}
+	}
 
-	err = s.ucal.CalculateAndRecord(now, times, s.recordCPUUtilization)
+	err = s.ucals[pid].CalculateAndRecord(now, times, s.recordCPUUtilization)
 	return err
 }
 

receiver/hostmetricsreceiver/internal/scraper/processscraper/ucal/cpu_utilization_calculator.go

@@ -50,13 +50,13 @@ func (c *CPUUtilizationCalculator) CalculateAndRecord(now pcommon.Timestamp, cur
 
 // cpuUtilization calculates the difference between 2 cpu.TimesStat using spent time between them
 func cpuUtilization(startStats *cpu.TimesStat, startTime pcommon.Timestamp, endStats *cpu.TimesStat, endTime pcommon.Timestamp) CPUUtilization {
-	elapsedTime := time.Duration(endTime - startTime)
+	elapsedTime := time.Duration(endTime - startTime).Seconds()
 	if elapsedTime <= 0 {
 		return CPUUtilization{}
 	}
 	return CPUUtilization{
-		User:   (endStats.User - startStats.User) / elapsedTime.Seconds(),
-		System: (endStats.System - startStats.System) / elapsedTime.Seconds(),
-		Iowait: (endStats.Iowait - startStats.Iowait) / elapsedTime.Seconds(),
+		User:   (endStats.User - startStats.User) / elapsedTime,
+		System: (endStats.System - startStats.System) / elapsedTime,
+		Iowait: (endStats.Iowait - startStats.Iowait) / elapsedTime,
 	}
 }