[Metricbeat][Kibana] Apply backoff when errored at getting usage stats

CHANGELOG.next.asciidoc

@@ -339,6 +339,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix SQL module mapping NULL values as string {pull}18955[18955] {issue}18898[18898
 - Fix ec2 disk and network metrics to use Sum statistic method. {pull}20680[20680]
 - Fill cloud.account.name with accountID if account alias doesn't exist. {pull}20736[20736]
+- The Kibana collector applies backoff when errored at getting usage stats {pull}20772[20772]
 - Update fields.yml in the azure module, missing metrics field. {pull}20918[20918]
 - The `elasticsearch/index` metricset only requests wildcard expansion for hidden indices if the monitored Elasticsearch cluster supports it. {pull}20938[20938]
 - Disable Kafka metricsets based on Jolokia by default. They require a different configuration. {pull}20989[20989]

metricbeat/module/kibana/stats/stats.go

@@ -38,9 +38,10 @@ func init() {
 }
 
 const (
-	statsPath             = "api/stats"
-	settingsPath          = "api/settings"
-	usageCollectionPeriod = 24 * time.Hour
+	statsPath              = "api/stats"
+	settingsPath           = "api/settings"
+	usageCollectionPeriod  = 24 * time.Hour
+	usageCollectionBackoff = 1 * time.Hour
 )
 
 var (
@@ -57,6 +58,7 @@ type MetricSet struct {
 	statsHTTP            *helper.HTTP
 	settingsHTTP         *helper.HTTP
 	usageLastCollectedOn time.Time
+	usageNextCollectOn   time.Time
 	isUsageExcludable    bool
 }
 
@@ -165,6 +167,10 @@ func (m *MetricSet) fetchStats(r mb.ReporterV2, now time.Time) error {
 
 		content, err = m.statsHTTP.FetchContent()
 		if err != nil {
+			if shouldCollectUsage {
+				// When errored in collecting the usage stats it may be counterproductive to try again on the next poll, try to collect the stats again after usageCollectionBackoff
+				m.usageNextCollectOn = now.Add(usageCollectionBackoff)
+			}
 			return err
 		}
 
@@ -215,5 +221,5 @@ func (m *MetricSet) calculateIntervalMs() int64 {
 }
 
 func (m *MetricSet) shouldCollectUsage(now time.Time) bool {
-	return now.Sub(m.usageLastCollectedOn) > usageCollectionPeriod
+	return now.Sub(m.usageLastCollectedOn) > usageCollectionPeriod && now.Sub(m.usageNextCollectOn) > 0
 }

metricbeat/module/kibana/stats/stats_test.go

@@ -23,6 +23,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 
@@ -48,12 +49,12 @@ func TestFetchUsage(t *testing.T) {
 				w.WriteHeader(503)
 
 			case 1: // second call
-				// Make sure exclude_usage is still false since first call failed
-				require.Equal(t, "false", excludeUsage)
+				// Make sure exclude_usage is true since first call failed and it should not try again until usageCollectionBackoff time has passed
+				require.Equal(t, "true", excludeUsage)
 				w.WriteHeader(200)
 
 			case 2: // third call
-				// Make sure exclude_usage is now true since second call succeeded
+				// Make sure exclude_usage is still true
 				require.Equal(t, "true", excludeUsage)
 				w.WriteHeader(200)
 			}
@@ -76,3 +77,40 @@ func TestFetchUsage(t *testing.T) {
 	// Third fetch
 	mbtest.ReportingFetchV2Error(f)
 }
+
+func TestShouldCollectUsage(t *testing.T) {
+	now := time.Now()
+
+	cases := map[string]struct {
+		usageLastCollectedOn time.Time
+		usageNextCollectOn   time.Time
+		expectedResult       bool
+	}{
+		"within_usage_collection_period": {
+			usageLastCollectedOn: now.Add(-1 * usageCollectionPeriod),
+			expectedResult:       false,
+		},
+		"after_usage_collection_period_but_before_next_scheduled_collection": {
+			usageLastCollectedOn: now.Add(-2 * usageCollectionPeriod),
+			usageNextCollectOn:   now.Add(3 * time.Hour),
+			expectedResult:       false,
+		},
+		"after_usage_collection_period_and_after_next_scheduled_collection": {
+			usageLastCollectedOn: now.Add(-2 * usageCollectionPeriod),
+			usageNextCollectOn:   now.Add(-1 * time.Hour),
+			expectedResult:       true,
+		},
+	}
+
+	for name, test := range cases {
+		t.Run(name, func(t *testing.T) {
+			m := MetricSet{
+				usageLastCollectedOn: test.usageLastCollectedOn,
+				usageNextCollectOn:   test.usageNextCollectOn,
+			}
+
+			actualResult := m.shouldCollectUsage(now)
+			require.Equal(t, test.expectedResult, actualResult)
+		})
+	}
+}