fix: don't fail merticbeat/windows/perfmon when no data is available (#…

…42803) (#42948)

* fix: don't fail merticbeat/windows/perfmon when no data is available

* add CHANGELOG.next.asciidoc entry

* fix: linter issue

* fix: linter issue

* fix: fix code according to PR comments

* refactor: make CollectData error handling testable

* fix: add mossing imports to windows/perfmon/reader_test.go

* fix: add mossing imports to windows/perfmon/reader_test.go

---------

Co-authored-by: Pierre HILBERT <pierre.hilbert@elastic.co>
(cherry picked from commit 0ea31fd)

Co-authored-by: stefans-elastic <stefan.stas@elastic.co>

CHANGELOG.next.asciidoc

@@ -157,6 +157,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Use namespace for GetListMetrics when exists in AWS {pull}41022[41022]
 - Fixed panic caused by uninitialized meraki device wifi0 and wifi1 struct pointers in the device WiFi data fetching. {issue}42745[42745] {pull}42746[42746]
 - Only fetch cluster-level index stats summary {issue}36019[36019] {pull}42901[42901]
+- Fixed an issue in Metricbeat's Windows module where data collection would fail if the data was unavailable. {issue}42802[42802] {pull}42803[42803]
 
 *Osquerybeat*
 

metricbeat/module/windows/perfmon/reader.go

@@ -96,13 +96,8 @@ func (re *Reader) Read() ([]mb.Event, error) {
 	// Some counters, such as rate counters, require two counter values in order to compute a displayable value. In this case we must call PdhCollectQueryData twice before calling PdhGetFormattedCounterValue.
 	// For more information, see Collecting Performance Data (https://docs.microsoft.com/en-us/windows/desktop/PerfCtrs/collecting-performance-data).
 	if err := re.query.CollectData(); err != nil {
-		// users can encounter the case no counters are found (services/processes stopped), this should not generate an event with the error message,
-		//could be the case the specific services are started after and picked up by the next RefreshCounterPaths func
-		if err == pdh.PDH_NO_COUNTERS { //nolint:errorlint // Bad linter! This is always errno or nil.
-			re.log.Warnf("%s %v", collectFailedMsg, err)
-		} else {
-			return nil, fmt.Errorf("%v: %w", collectFailedMsg, err)
-		}
+		err = re.handleCollectDataError(err)
+		return nil, err
 	}
 
 	// Get the values.
@@ -121,6 +116,19 @@ func (re *Reader) Read() ([]mb.Event, error) {
 	return events, nil
 }
 
+func (re *Reader) handleCollectDataError(err error) error {
+	// users can encounter the case no counters are found (services/processes stopped), this should not generate an event with the error message,
+	//could be the case the specific services are started after and picked up by the next RefreshCounterPaths func
+	if err == pdh.PDH_NO_COUNTERS || err == pdh.PDH_NO_DATA { //nolint:errorlint // linter complains about comparing error using '==' operator but here error is always of type pdh.PdhErrno (or nil) so `errors.Is` is redundant here
+		re.log.Warnf("%s %v", collectFailedMsg, err)
+
+		// Ensure the returned error is nil to prevent the Elastic Agent from transitioning to an UNHEALTHY state.
+		return nil
+	}
+
+	return fmt.Errorf("%v: %w", collectFailedMsg, err)
+}
+
 func (re *Reader) getValues() (map[string][]pdh.CounterValue, error) {
 	var val map[string][]pdh.CounterValue
 	// Sleep for one second before collecting the second raw value-

metricbeat/module/windows/perfmon/reader_test.go

@@ -20,11 +20,13 @@
 package perfmon
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 
 	"github.com/elastic/beats/v7/metricbeat/helper/windows/pdh"
+	"github.com/elastic/elastic-agent-libs/logp"
 )
 
 func TestGetCounter(t *testing.T) {
@@ -153,3 +155,46 @@ func TestIsWildcard(t *testing.T) {
 	result = isWildcard(queries, instance)
 	assert.False(t, result)
 }
+
+func Test_handleCollectDataError(t *testing.T) {
+	tests := []struct {
+		name string
+
+		mockErr        error
+		expectedErrMsg string
+	}{
+		{
+			name: "no counters error",
+
+			mockErr:        pdh.PDH_NO_COUNTERS,
+			expectedErrMsg: "",
+		},
+		{
+			name: "no data error",
+
+			mockErr:        pdh.PDH_NO_DATA,
+			expectedErrMsg: "",
+		},
+		{
+			name: "unexpected error",
+
+			mockErr:        errors.New("test error"),
+			expectedErrMsg: "failed collecting counter values: test error",
+		},
+	}
+
+	reader := &Reader{
+		log: logp.NewLogger("perfmon"),
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := reader.handleCollectDataError(tt.mockErr)
+			if tt.expectedErrMsg == "" {
+				assert.NoError(t, err)
+			} else {
+				assert.EqualError(t, err, tt.expectedErrMsg)
+			}
+		})
+	}
+}