Fix index out of bounds error in solr input plugin (#3683)

(cherry picked from commit 9d559292a5)

plugins/inputs/solr/solr.go

@@ -246,6 +246,9 @@ func addAdminCoresStatusToAcc(acc telegraf.Accumulator, adminCoreStatus *AdminCo
 // Add core metrics section to accumulator
 func addCoreMetricsToAcc(acc telegraf.Accumulator, core string, mBeansData *MBeansData, time time.Time) error {
 	var coreMetrics map[string]Core
+	if len(mBeansData.SolrMbeans) < 2 {
+		return fmt.Errorf("no core metric data to unmarshall")
+	}
 	if err := json.Unmarshal(mBeansData.SolrMbeans[1], &coreMetrics); err != nil {
 		return err
 	}
@@ -274,9 +277,14 @@ func addCoreMetricsToAcc(acc telegraf.Accumulator, core string, mBeansData *MBea
 func addQueryHandlerMetricsToAcc(acc telegraf.Accumulator, core string, mBeansData *MBeansData, time time.Time) error {
 	var queryMetrics map[string]QueryHandler
 
+	if len(mBeansData.SolrMbeans) < 4 {
+		return fmt.Errorf("no query handler metric data to unmarshall")
+	}
+
 	if err := json.Unmarshal(mBeansData.SolrMbeans[3], &queryMetrics); err != nil {
 		return err
 	}
+
 	for name, metrics := range queryMetrics {
 		coreFields := map[string]interface{}{
 			"15min_rate_reqs_per_second": metrics.Stats.One5minRateReqsPerSecond,
@@ -310,6 +318,9 @@ func addQueryHandlerMetricsToAcc(acc telegraf.Accumulator, core string, mBeansDa
 func addUpdateHandlerMetricsToAcc(acc telegraf.Accumulator, core string, mBeansData *MBeansData, time time.Time) error {
 	var updateMetrics map[string]UpdateHandler
 
+	if len(mBeansData.SolrMbeans) < 6 {
+		return fmt.Errorf("no update handler metric data to unmarshall")
+	}
 	if err := json.Unmarshal(mBeansData.SolrMbeans[5], &updateMetrics); err != nil {
 		return err
 	}
@@ -364,6 +375,9 @@ func getFloat(unk interface{}) float64 {
 
 // Add cache metrics section to accumulator
 func addCacheMetricsToAcc(acc telegraf.Accumulator, core string, mBeansData *MBeansData, time time.Time) error {
+	if len(mBeansData.SolrMbeans) < 8 {
+		return fmt.Errorf("no cache metric data to unmarshall")
+	}
 	var cacheMetrics map[string]Cache
 	if err := json.Unmarshal(mBeansData.SolrMbeans[7], &cacheMetrics); err != nil {
 		return err

plugins/inputs/solr/solr_test.go

@@ -60,3 +60,44 @@ func createMockServer() *httptest.Server {
 		}
 	}))
 }
+
+func TestNoCoreDataHandling(t *testing.T) {
+	ts := createMockNoCoreDataServer()
+	solr := NewSolr()
+	solr.Servers = []string{ts.URL}
+	var acc testutil.Accumulator
+	require.NoError(t, solr.Gather(&acc))
+
+	acc.AssertContainsTaggedFields(t, "solr_admin",
+		solrAdminMainCoreStatusExpected,
+		map[string]string{"core": "main"})
+
+	acc.AssertContainsTaggedFields(t, "solr_admin",
+		solrAdminCore1StatusExpected,
+		map[string]string{"core": "core1"})
+
+	acc.AssertDoesNotContainMeasurement(t, "solr_core")
+	acc.AssertDoesNotContainMeasurement(t, "solr_queryhandler")
+	acc.AssertDoesNotContainMeasurement(t, "solr_updatehandler")
+	acc.AssertDoesNotContainMeasurement(t, "solr_handler")
+
+}
+
+func createMockNoCoreDataServer() *httptest.Server {
+	var nodata string
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if strings.Contains(r.URL.Path, "/solr/admin/cores") {
+			w.WriteHeader(http.StatusOK)
+			fmt.Fprintln(w, statusResponse)
+		} else if strings.Contains(r.URL.Path, "solr/main/admin") {
+			w.WriteHeader(http.StatusOK)
+			fmt.Fprintln(w, nodata)
+		} else if strings.Contains(r.URL.Path, "solr/core1/admin") {
+			w.WriteHeader(http.StatusOK)
+			fmt.Fprintln(w, nodata)
+		} else {
+			w.WriteHeader(http.StatusNotFound)
+			fmt.Fprintln(w, "nope")
+		}
+	}))
+}