Fix and improve error handling in mongodb collection stats (#6230)

plugins/inputs/mongodb/README.md

@@ -44,6 +44,10 @@ Telegraf logs similar to:
 Error in input [mongodb]: not authorized on admin to execute command { serverStatus: 1, recordStats: 0 }
 ```
 
+Some permission related errors are logged at debug level, you can check these
+messages by setting `debug = true` in the agent section of the configuration or
+by running Telegraf with the `--debug` argument.
+
 ### Metrics:
 
 - mongodb

plugins/inputs/mongodb/mongodb_server.go

@@ -31,6 +31,14 @@ func IsAuthorization(err error) bool {
 	return strings.Contains(err.Error(), "not authorized")
 }
 
+func authLogLevel(err error) string {
+	if IsAuthorization(err) {
+		return "D!"
+	} else {
+		return "E!"
+	}
+}
+
 func (s *Server) gatherOplogStats() *OplogStats {
 	stats := &OplogStats{}
 	localdb := s.Session.DB("local")
@@ -44,22 +52,14 @@ func (s *Server) gatherOplogStats() *OplogStats {
 			if err == mgo.ErrNotFound {
 				continue
 			}
-			if IsAuthorization(err) {
+			log.Printf("%s [inputs.mongodb] Error getting first oplog entry: %v", authLogLevel(err), err)
-				log.Println("D! Error getting first oplog entry (" + err.Error() + ")")
-			} else {
-				log.Println("E! Error getting first oplog entry (" + err.Error() + ")")
-			}
 			return stats
 		}
 		if err := localdb.C(collection_name).Find(query).Sort("-$natural").Limit(1).One(&op_last); err != nil {
 			if err == mgo.ErrNotFound || IsAuthorization(err) {
 				continue
 			}
-			if IsAuthorization(err) {
+			log.Printf("%s [inputs.mongodb] Error getting first oplog entry: %v", authLogLevel(err), err)
-				log.Println("D! Error getting first oplog entry (" + err.Error() + ")")
-			} else {
-				log.Println("E! Error getting first oplog entry (" + err.Error() + ")")
-			}
 			return stats
 		}
 	}
@@ -70,6 +70,45 @@ func (s *Server) gatherOplogStats() *OplogStats {
 	return stats
 }
 
+func (s *Server) gatherCollectionStats(colStatsDbs []string) (*ColStats, error) {
+	names, err := s.Session.DatabaseNames()
+	if err != nil {
+		return nil, err
+	}
+
+	results := &ColStats{}
+	for _, db_name := range names {
+		if stringInSlice(db_name, colStatsDbs) || len(colStatsDbs) == 0 {
+			var colls []string
+			colls, err = s.Session.DB(db_name).CollectionNames()
+			if err != nil {
+				log.Printf("E! [inputs.mongodb] Error getting collection names: %v", err)
+				continue
+			}
+			for _, col_name := range colls {
+				col_stat_line := &ColStatsData{}
+				err = s.Session.DB(db_name).Run(bson.D{
+					{
+						Name:  "collStats",
+						Value: col_name,
+					},
+				}, col_stat_line)
+				if err != nil {
+					log.Printf("%s [inputs.mongodb] Error getting col stats from %q: %v", authLogLevel(err), col_name, err)
+					continue
+				}
+				collection := &Collection{
+					Name:         col_name,
+					DbName:       db_name,
+					ColStatsData: col_stat_line,
+				}
+				results.Collections = append(results.Collections, *collection)
+			}
+		}
+	}
+	return results, nil
+}
+
 func (s *Server) gatherData(acc telegraf.Accumulator, gatherDbStats bool, gatherColStats bool, colStatsDbs []string) error {
 	s.Session.SetMode(mgo.Eventual, true)
 	s.Session.SetSocketTimeout(0)
@@ -112,9 +151,9 @@ func (s *Server) gatherData(acc telegraf.Accumulator, gatherDbStats bool, gather
 	}, &resultShards)
 	if err != nil {
 		if IsAuthorization(err) {
-			log.Println("D! Error getting database shard stats (" + err.Error() + ")")
+			log.Printf("D! [inputs.mongodb] Error getting database shard stats: %v", err)
 		} else {
-			log.Println("E! Error getting database shard stats (" + err.Error() + ")")
+			log.Printf("E! [inputs.mongodb] Error getting database shard stats: %v", err)
 		}
 	}
 
@@ -125,7 +164,7 @@ func (s *Server) gatherData(acc telegraf.Accumulator, gatherDbStats bool, gather
 		names := []string{}
 		names, err = s.Session.DatabaseNames()
 		if err != nil {
-			log.Println("E! Error getting database names (" + err.Error() + ")")
+			log.Printf("E! [inputs.mongodb] Error getting database names: %v", err)
 		}
 		for _, db_name := range names {
 			db_stat_line := &DbStatsData{}
@@ -136,7 +175,7 @@ func (s *Server) gatherData(acc telegraf.Accumulator, gatherDbStats bool, gather
 				},
 			}, db_stat_line)
 			if err != nil {
-				log.Println("E! Error getting db stats from " + db_name + "(" + err.Error() + ")")
+				log.Printf("E! [inputs.mongodb] Error getting db stats from %q: %v", db_name, err)
 			}
 			db := &Db{
 				Name:        db_name,
@@ -147,41 +186,9 @@ func (s *Server) gatherData(acc telegraf.Accumulator, gatherDbStats bool, gather
 		}
 	}
 
-	result_col_stats := &ColStats{}
+	result_col_stats, err := s.gatherCollectionStats(colStatsDbs)
-	if gatherColStats == true {
-		names := []string{}
-		names, err = s.Session.DatabaseNames()
 	if err != nil {
-			log.Println("E! Error getting database names (" + err.Error() + ")")
+		return err
-		}
-		for _, db_name := range names {
-			if stringInSlice(db_name, colStatsDbs) || len(colStatsDbs) == 0 {
-				var colls []string
-				colls, err = s.Session.DB(db_name).CollectionNames()
-				if err != nil {
-					log.Println("E! Error getting collection names (" + err.Error() + ")")
-				}
-				for _, col_name := range colls {
-					col_stat_line := &ColStatsData{}
-					err = s.Session.DB(db_name).Run(bson.D{
-						{
-							Name:  "collStats",
-							Value: col_name,
-						},
-					}, col_stat_line)
-					if err != nil {
-						log.Println("E! Error getting col stats from " + col_name + "(" + err.Error() + ")")
-						continue
-					}
-					collection := &Collection{
-						Name:         col_name,
-						DbName:       db_name,
-						ColStatsData: col_stat_line,
-					}
-					result_col_stats.Collections = append(result_col_stats.Collections, *collection)
-				}
-			}
-		}
 	}
 
 	result := &MongoStatus{