[system] - Add a flag to the system module to control whether metrics…

… failures mark agent as degraded (#42160)

* chore: initial commit

* doc and test cases

* lint

* remove errors.Is

* chore: notice

* update docs

* Update metricbeat/mb/event.go

Co-authored-by: Craig MacKenzie <craig.mackenzie@elastic.co>

* remove references

* remove sleep

---------

Co-authored-by: Craig MacKenzie <craig.mackenzie@elastic.co>
(cherry picked from commit 7a2f8d4)

metricbeat/mb/event.go

@@ -223,6 +223,9 @@ type PartialMetricsError struct {
 }
 
 func (p PartialMetricsError) Error() string {
+	if p.Err == nil {
+		return ""
+	}
 	return p.Err.Error()
 }
 

metricbeat/module/system/_meta/config.yml

@@ -17,6 +17,7 @@
   process.include_top_n:
     by_cpu: 5      # include top 5 processes by CPU
     by_memory: 5   # include top 5 processes by memory
+  degrade_on_partial: false # mark metricset as degraded if partial metrics are emitted 
 # Configure the mount point of the host’s filesystem for use in monitoring a host from within a container
 # hostfs: "/hostfs"
 

metricbeat/module/system/process/process.go

@@ -45,9 +45,10 @@ func init() {
 // MetricSet that fetches process metrics.
 type MetricSet struct {
 	mb.BaseMetricSet
-	stats  *process.Stats
-	perCPU bool
-	setpid int
+	stats            *process.Stats
+	perCPU           bool
+	setpid           int
+	degradeOnPartial bool
 }
 
 // New creates and returns a new MetricSet.
@@ -72,7 +73,12 @@ func New(base mb.BaseMetricSet) (mb.MetricSet, error) {
 	if config.Pid != 0 && config.Procs[0] != ".*" {
 		logp.L().Warnf("`process.pid` set to %d, but `processes` is set to a non-default value. Metricset will only report metrics for pid %d", config.Pid, config.Pid)
 	}
-
+	degradedConf := struct {
+		DegradeOnPartial bool `config:"degrade_on_partial"`
+	}{}
+	if err := base.Module().UnpackConfig(&degradedConf); err != nil {
+		logp.L().Warnf("Failed to unpack config; degraded mode will be disabled for partial metrics: %v", err)
+	}
 	m := &MetricSet{
 		BaseMetricSet: base,
 		stats: &process.Stats{
@@ -88,7 +94,8 @@ func New(base mb.BaseMetricSet) (mb.MetricSet, error) {
 				IgnoreRootCgroups: true,
 			},
 		},
-		perCPU: config.IncludePerCPU,
+		perCPU:           config.IncludePerCPU,
+		degradeOnPartial: degradedConf.DegradeOnPartial,
 	}
 
 	m.setpid = config.Pid
@@ -119,6 +126,9 @@ func (m *MetricSet) Fetch(r mb.ReporterV2) error {
 			// return only if the error is fatal in nature
 			return fmt.Errorf("process stats: %w", err)
 		} else if (err != nil && errors.Is(err, process.NonFatalErr{})) {
+			if m.degradeOnPartial {
+				return fmt.Errorf("error fetching process list: %w", err)
+			}
 			err = mb.PartialMetricsError{Err: err}
 		}
 
@@ -138,6 +148,9 @@ func (m *MetricSet) Fetch(r mb.ReporterV2) error {
 			// return only if the error is fatal in nature
 			return fmt.Errorf("error fetching pid %d: %w", m.setpid, err)
 		} else if (err != nil && errors.Is(err, process.NonFatalErr{})) {
+			if m.degradeOnPartial {
+				return fmt.Errorf("error fetching process list: %w", err)
+			}
 			err = mb.PartialMetricsError{Err: err}
 		}
 		// if error is non-fatal, emit partial metrics.

metricbeat/module/system/process/process_test.go

@@ -26,6 +26,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 
+	"github.com/elastic/beats/v7/metricbeat/mb"
 	mbtest "github.com/elastic/beats/v7/metricbeat/mb/testing"
 	_ "github.com/elastic/beats/v7/metricbeat/module/system"
 	"github.com/elastic/elastic-agent-libs/logp"
@@ -55,6 +56,32 @@ func TestFetch(t *testing.T) {
 		events[0].BeatEvent("system", "process").Fields.StringToPrint())
 }
 
+func TestFetchDegradeOnPartial(t *testing.T) {
+	logp.DevelopmentSetup()
+	config := getConfig()
+	config["degrade_on_partial"] = true
+
+	f := mbtest.NewReportingMetricSetV2Error(t, config)
+	events, errs := mbtest.ReportingFetchV2Error(f)
+	if len(errs) > 0 {
+		for _, err := range errs {
+			assert.NotErrorIsf(t, err, &mb.PartialMetricsError{}, "Expected non-fatal error, got %v", err)
+		}
+	} else {
+		assert.NotEmpty(t, events)
+
+		events, errs = mbtest.ReportingFetchV2Error(f)
+		for _, err := range errs {
+			assert.ErrorIsf(t, err, process.NonFatalErr{}, "Expected non-fatal error, got %v", err)
+		}
+		assert.NotEmpty(t, events)
+
+		t.Logf("fetched %d events, showing events[0]:", len(events))
+		t.Logf("%s/%s event: %+v", f.Module().Name(), f.Name(),
+			events[0].BeatEvent("system", "process").Fields.StringToPrint())
+	}
+}
+
 func TestFetchSinglePid(t *testing.T) {
 	logp.DevelopmentSetup()
 

metricbeat/module/system/process_summary/process_summary.go

@@ -30,6 +30,7 @@ import (
 	"github.com/elastic/beats/v7/libbeat/common/transform/typeconv"
 	"github.com/elastic/beats/v7/metricbeat/mb"
 	"github.com/elastic/beats/v7/metricbeat/mb/parse"
+	"github.com/elastic/elastic-agent-libs/logp"
 	"github.com/elastic/elastic-agent-libs/mapstr"
 	"github.com/elastic/elastic-agent-system-metrics/metric/system/process"
 	"github.com/elastic/elastic-agent-system-metrics/metric/system/resolve"
@@ -50,17 +51,28 @@ func init() {
 // multiple fetch calls.
 type MetricSet struct {
 	mb.BaseMetricSet
-	sys resolve.Resolver
+	sys              resolve.Resolver
+	degradeOnPartial bool
 }
 
 // New create a new instance of the MetricSet
 // Part of new is also setting up the configuration by processing additional
 // configuration entries if needed.
 func New(base mb.BaseMetricSet) (mb.MetricSet, error) {
-	sys := base.Module().(resolve.Resolver)
+	sys, ok := base.Module().(resolve.Resolver)
+	if !ok {
+		return nil, fmt.Errorf("resolver cannot be cast from the module")
+	}
+	degradedConf := struct {
+		DegradeOnPartial bool `config:"degrade_on_partial"`
+	}{}
+	if err := base.Module().UnpackConfig(&degradedConf); err != nil {
+		logp.L().Warnf("Failed to unpack config; degraded mode will be disabled for partial metrics: %v", err)
+	}
 	return &MetricSet{
-		BaseMetricSet: base,
-		sys:           sys,
+		BaseMetricSet:    base,
+		sys:              sys,
+		degradeOnPartial: degradedConf.DegradeOnPartial,
 	}, nil
 }
 
@@ -74,6 +86,9 @@ func (m *MetricSet) Fetch(r mb.ReporterV2) error {
 		// return only if the error is fatal in nature
 		return fmt.Errorf("error fetching process list: %w", degradeErr)
 	} else if (degradeErr != nil && errors.Is(degradeErr, process.NonFatalErr{})) {
+		if m.degradeOnPartial {
+			return fmt.Errorf("error fetching process list: %w", degradeErr)
+		}
 		degradeErr = mb.PartialMetricsError{Err: degradeErr}
 	}
 

metricbeat/module/system/process_summary/process_summary_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"github.com/elastic/beats/v7/metricbeat/mb"
 	mbtest "github.com/elastic/beats/v7/metricbeat/mb/testing"
 	_ "github.com/elastic/beats/v7/metricbeat/module/system"
 	"github.com/elastic/elastic-agent-libs/logp"
@@ -58,6 +59,27 @@ func TestFetch(t *testing.T) {
 	require.NoError(t, err)
 
 }
+func TestFetchDegradeOnPartial(t *testing.T) {
+	logp.DevelopmentSetup()
+	config := getConfig()
+	config["degrade_on_partial"] = true
+
+	f := mbtest.NewReportingMetricSetV2Error(t, config)
+	events, errs := mbtest.ReportingFetchV2Error(f)
+	if len(errs) > 0 {
+		for _, err := range errs {
+			assert.NotErrorIsf(t, err, &mb.PartialMetricsError{}, "Expected non-fatal error, got %v", err)
+		}
+	} else {
+		require.NotEmpty(t, events)
+		event := events[0].BeatEvent("system", "process_summary").Fields
+		t.Logf("%s/%s event: %+v", f.Module().Name(), f.Name(),
+			event.StringToPrint())
+
+		_, err := event.GetValue("system.process.summary")
+		require.NoError(t, err)
+	}
+}
 
 func TestStateNames(t *testing.T) {
 	logp.DevelopmentSetup()
@@ -80,7 +102,8 @@ func TestStateNames(t *testing.T) {
 	assert.NotZero(t, event["total"])
 
 	var sum int
-	total := event["total"].(int)
+	total, ok := event["total"].(int)
+	require.Truef(t, ok, "Expected int got %T", event["total"])
 	for key, val := range event {
 		if key == "total" {
 			continue

metricbeat/modules.d/system.yml

@@ -20,6 +20,7 @@
   process.include_top_n:
     by_cpu: 5      # include top 5 processes by CPU
     by_memory: 5   # include top 5 processes by memory
+  degrade_on_partial: false # mark metricset as degraded if partial metrics are emitted 
 # Configure the mount point of the host’s filesystem for use in monitoring a host from within a container
 # hostfs: "/hostfs"