PMM-14431 Refactor.

Author: JiriCtvrtka

exporter/metrics.go

@@ -219,41 +219,51 @@ func allReservedNames(client *mongo.Client) ([]string, error) {
 	for _, dbName := range dbs {
 		fmt.Printf("Database: %s\n", dbName)
 		db := client.Database(dbName)
-		collCursor, err := db.ListCollections(ctx, struct{}{})
+		names, err := getReservedNamesForDB(ctx, db, dbName)
 		if err != nil {
-			return reservedNames, errors.Wrapf(err, "ListCollections failed for db %s", dbName)
+			return reservedNames, err
 		}
-		defer collCursor.Close(ctx) //nolint:errcheck
-		for collCursor.Next(ctx) {
-			var collInfo struct {
-				Name string `bson:"name"`
-				Type string `bson:"type"`
-			}
-			if err := collCursor.Decode(&collInfo); err != nil {
-				return reservedNames, errors.Wrapf(err, "Decode failed for collection in db %s", dbName)
-			}
-			reservedNames = append(reservedNames, collInfo.Name)
-			if collInfo.Type == "view" {
-				continue // skip views
-			}
-			coll := db.Collection(collInfo.Name)
-			cursor, err := coll.Indexes().List(ctx)
-			if err != nil {
-				continue // skip if cannot list indexes
+		reservedNames = append(reservedNames, names...)
+	}
+
+	return reservedNames, nil
+}
+
+func getReservedNamesForDB(ctx context.Context, db *mongo.Database, dbName string) ([]string, error) {
+	reservedNames := []string{}
+	collCursor, err := db.ListCollections(ctx, struct{}{})
+	if err != nil {
+		return reservedNames, errors.Wrapf(err, "ListCollections failed for db %s", dbName)
+	}
+	defer collCursor.Close(ctx) //nolint:errcheck
+	for collCursor.Next(ctx) {
+		var collInfo struct {
+			Name string `bson:"name"`
+			Type string `bson:"type"`
+		}
+		if err := collCursor.Decode(&collInfo); err != nil {
+			return reservedNames, errors.Wrapf(err, "Decode failed for collection in db %s", dbName)
+		}
+		reservedNames = append(reservedNames, collInfo.Name)
+		if collInfo.Type == "view" {
+			continue // skip views
+		}
+		coll := db.Collection(collInfo.Name)
+		cursor, err := coll.Indexes().List(ctx)
+		if err != nil {
+			continue // skip if cannot list indexes
+		}
+		defer cursor.Close(ctx) //nolint:errcheck
+		for cursor.Next(ctx) {
+			var indexDoc map[string]interface{}
+			if err := cursor.Decode(&indexDoc); err != nil {
+				continue
 			}
-			defer cursor.Close(ctx) //nolint:errcheck
-			for cursor.Next(ctx) {
-				var indexDoc map[string]interface{}
-				if err := cursor.Decode(&indexDoc); err != nil {
-					continue
-				}
-				if name, ok := indexDoc["name"].(string); ok {
-					reservedNames = append(reservedNames, name)
-				}
+			if name, ok := indexDoc["name"].(string); ok {
+				reservedNames = append(reservedNames, name)
 			}
 		}
 	}
-
 	return reservedNames, nil
 }