Random Examine index failure

[gordonsaxby]

Umbraco v10.8.8, hosted on Azure

It appears to be random, but we sometimes get this error.

System.NullReferenceException: Object reference not set to an instance of an object.
   at Lucene.Net.QueryParsers.Classic.QueryParser.Jj_add_error_token(Int32 kind, Int32 pos)
   at Lucene.Net.QueryParsers.Classic.QueryParser.Jj_scan_token(Int32 kind)
   at Lucene.Net.QueryParsers.Classic.QueryParser.Jj_3R_3()
   at Lucene.Net.QueryParsers.Classic.QueryParser.Jj_rescan_token()
   at Lucene.Net.QueryParsers.Classic.QueryParser.GenerateParseException()
   at Lucene.Net.QueryParsers.Classic.QueryParser.Jj_consume_token(Int32 kind)
   at Lucene.Net.QueryParsers.Classic.QueryParser.Clause(String field)
   at Lucene.Net.QueryParsers.Classic.QueryParser.Query(String field)
   at Lucene.Net.QueryParsers.Classic.QueryParser.TopLevelQuery(String field)
   at Lucene.Net.QueryParsers.Classic.QueryParserBase.Parse(String query)
   at Examine.Lucene.Search.LuceneSearchQueryBase.GetFieldInternalQuery(String fieldName, IExamineValue fieldValue, Boolean useQueryParser)
   at Examine.Lucene.Search.LuceneSearchQuery.Search(QueryOptions options)
   at Examine.Lucene.Search.LuceneBooleanOperation.Execute(QueryOptions options)

The only way to solve it is to manually delete the Examine folders and restart the website.

The code is below and it fails on "query.Execute":

        try
        {
            var events = new List<IPublishedContent?>();
            totalEvents = 0;

            startDate = startDate ?? DateTime.Now.Date;
            endDate = endDate ?? DateTime.MaxValue;

            if (_examineManager.TryGetIndex(AppConstants.Events.IndexName, out var index))
            {
                var searcher = index.Searcher;
                var query = searcher
                    .CreateQuery(IndexTypes.Content)
                    .NodeTypeAlias(EventPage.ModelTypeAlias)
                    .And()
                    .Field("pathSearchable", rootNodeId.ToString());

                query = query
                    .And()
                    .RangeQuery(new[] { AppConstants.Events.InstanceSearchableField }, startDate, endDate);

                if (categories?.Any() == true)
                {
                    query = query
                        .And()
                        .GroupedOr(new[] { AppConstants.Events.CategorySearchableField }, categories);
                }

                query.OrderBy(new SortableField(AppConstants.Events.FirstInstanceSearchableField, SortType.Long));

                var results = query.Execute(new QueryOptions(pageSize * (pageIndex - 1), pageSize));

                if (_umbracoContextAccessor.TryGetUmbracoContext(out var umbracoContext))
                {
                    foreach (var result in results)
                    {
                        var publishedContent = umbracoContext.Content?.GetById(int.Parse(result.Id));
                        if (publishedContent == null)
                            continue;

                        events.Add(publishedContent);
                    }

                    totalEvents = (int)results.TotalItemCount;
                }
            }

            return events;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, $"EventsService:GetPagedBlogPosts failed - {ex}");

            totalEvents = 0;
            return new List<IPublishedContent>();
        }

[Shazwazza]

Sorry for the delay but this is fixed in later Examine versions, just make sure you're on the latest. Problem is because of concurrent access to a QueryParser which shouldn't be done.