I seem to keep butting up against lock or already closed exception errors, with Examine search functionality. I am using an Azure Web App, that I have to keep at one instance, which seemed to work for a week or so, and then I started getting the Lucene "AlreadyClosedException" errors in the log, and my search functionality stopped.

Here's my code for a predictive search function:

    private UmbracoHelper _uHelper { get; set; }

    public SearchHelper(UmbracoHelper uHelper)
        {
        _uHelper = uHelper;
        }

    public SearchViewModel GetSearchResults(string query, string culture, string[] allKeys, string fieldName = "__Published")
        {
        IIndex index;

        SearchViewModel searchResponse = new SearchViewModel()
            {
            Results = new List<SearchResultsModel>(),
            ResultCount = 0,
            SearchTerm = query
            };

        if(!ExamineManager.Instance.TryGetIndex("ExternalIndex", out index) || !(index is IUmbracoIndex))
            throw new InvalidOperationException("The required index ExternalIndex was not found");

        string[] fields = new string[8]
        {
           "basePartNumber",
           "productName",
           "name",
           "bodyText",
           "productFeatures",
           "specifications",
           "tags",
           "associations"
        };

        getAndSetSearchResults(searchResponse, query, culture, index, fields, fieldName, false);

        return searchResponse;
        }

    private void getAndSetSearchResults(SearchViewModel searchResponse, string query, string culture, IIndex index, string[] fields, string fieldName, bool triedConfigSKU)
        {

        var booleanOperation = index.GetSearcher().CreateQuery("content", BooleanOperation.And).ManagedQuery(query.Length > 2 ? query.ToLower() + "*" : query.ToLower(), fields).And().Field(fieldName, "y");

        long totalRecords;
        IEnumerable<PublishedSearchResult> publishedContentSearchResults = _uHelper.ContentQuery.Search((IQueryExecutor)booleanOperation.Not().Field("hideFromSearch", "1"), 0, 25, out totalRecords);
        searchResponse.ResultCount = Convert.ToInt32(totalRecords);

        var hyphenProductName = ContainsHyphenProductName(query.ToString().ToUpper());
        if(totalRecords == 0 && triedConfigSKU == false)
            {
            // Try it as a configured SKU by searching up to the hyphen
            publishedContentSearchResults = null;
            getAndSetSearchResults(searchResponse, !String.IsNullOrEmpty(hyphenProductName) ? hyphenProductName : (query.Contains('-') ? query.Substring(0, query.IndexOf('-')) : query), culture, index, fields, fieldName, true);
            }

        foreach(PublishedSearchResult publishedSearchResult in publishedContentSearchResults.OrderByDescending(x => x.Score))
            {
            IPublishedContent content = publishedSearchResult.Content;

            if(!searchResponse.Results.Where(x => x.Id == content.Id).Any() && !content.Ancestors().Where(x => x.Name.ToUpper() == "DISCONTINUED").Any())
                {
                if(content.Value<Boolean>("UmbracoNavhide") == false)
                    {
                    searchResponse.Results.Add(new SearchResultsModel()
                        {
                        Id = content.Id,
                        Name = content.Name(culture),
                        Url = content.Url(culture, UrlMode.Auto),
                        BodyText = content.GetProperty("bodyText"),
                        ProductName = content.Value<string>("productName"),
                        ProductImageUrl = content.Value<IPublishedContent>("listingPhoto", (string)null, (string)null, new Fallback(), (IPublishedContent)null)?.Url,
                        DocType = content.ContentType.Alias,
                        Tags = content.Value<String[]>("tags")
                        });
                    }
                }
            }
        }

The error I see is:

 Lucene.Net.Store.AlreadyClosedException: this IndexReader is closed
   at Lucene.Net.Index.IndexReader.EnsureOpen() in d:\Lucene.Net\FullRepo\trunk\src\core\Index\IndexReader.cs:line 204
   at Lucene.Net.Index.DirectoryReader.GetFieldNames(FieldOption fieldNames) in d:\Lucene.Net\FullRepo\trunk\src\core\Index\DirectoryReader.cs:line 1055
   at Examine.LuceneEngine.Providers.LuceneSearcher.GetAllIndexedFields() in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\LuceneSearcher.cs:line 101
   at Examine.LuceneEngine.Providers.BaseLuceneSearcher.CreateQuery(String category, BooleanOperation defaultOperation, Analyzer luceneAnalyzer, LuceneSearchOptions searchOptions) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\BaseLuceneSearcher.cs:line 64
   at Examine.LuceneEngine.Providers.BaseLuceneSearcher.CreateQuery(String category, BooleanOperation defaultOperation) in C:\projects\examine-qvx04\src\Examine\LuceneEngine\Providers\BaseLuceneSearcher.cs:line 49
   at USD.CMS.Helpers.SearchHelper.getAndSetSearchResults(SearchViewModel searchResponse, String query, String culture, IIndex index, String[] fields, String fieldName, Boolean triedConfigSKU) in C:\Users\jason.delaplain\Source\Repos\USD\USD-Umbraco\USD.CMS\Helpers\SearchHelper.cs:line 59
   at USD.CMS.Helpers.SearchHelper.GetSearchResults(String query, String culture, String[] allKeys, String fieldName) in C:\Users\jason\Source\Repos\USD\USD-Umbraco\USD.CMS\Helpers\SearchHelper.cs:line 51
   at USD.CMS.Controllers.SearchController.SubmitSearchForm(SearchViewModel model) in C:\Users\jason\Source\Repos\USD\USD-Umbraco\USD.CMS\Controllers\SearchController.cs:line 44
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
   at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c.<BeginInvokeSynchronousActionMethod>b__9_0(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_0.<InvokeActionMethodFilterAsynchronouslyRecursive>b__0()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass7_0.<BeginInvokeActionMethodWithFilters>b__1(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_6.<BeginInvokeAction>b__4()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_1.<BeginInvokeAction>b__1(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.<>c.<BeginExecuteCore>b__152_1(IAsyncResult asyncResult, ExecuteCoreState innerState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.<>c.<BeginExecute>b__151_2(IAsyncResult asyncResult, Controller controller)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult)
   at System.Web.Mvc.MvcHandler.<>c.<BeginProcessRequest>b__20_1(IAsyncResult asyncResult, ProcessRequestState innerState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)
   at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

We're wanting (trying) to go live with the entire backend of our website switched out to Umbraco, but this could be a deal breaker. Especially since I'm not seeing much on the forums in the terms of replies or fixes.