We have a multisite Umbraco installation which has been upgraded from 7.5.11 to 7.10.4 since we've been getting this error (on 7.5.11):

2018-01-15 01:36:43,393 [P156252/D4115/T57] ERROR UmbracoExamine.DataServices.UmbracoLogService - Provider=PageSearchIndexer, NodeId=-1 System.Exception: Cannot index queue items, the index is currently locked,, IndexSet: PageSearchIndexSet

It was working fine (7.10.4) on the temporary domains for each of the sites until the hostnames were changed to the live domains.

It was fine the first day but then the site started crashing occasionally and this error started appearing on the logs every few seconds:

2018-07-08 05:32:08,361 [P39896/D2/T100] ERROR Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache - Could not load data from Examine index for media, the app domain is most likely in a shutdown state Lucene.Net.Store.AlreadyClosedException: this IndexReader is closed at Lucene.Net.Index.IndexReader.EnsureOpen() at Lucene.Net.Index.DirectoryReader.GetFieldNames(FieldOption fieldNames) at Examine.LuceneEngine.Providers.LuceneSearcher.GetSearchFields() at UmbracoExamine.UmbracoExamineSearcher.GetSearchFields() at Examine.LuceneEngine.Providers.BaseLuceneSearcher.CreateSearchCriteria(String type, BooleanOperation defaultOperation) at UmbracoExamine.UmbracoExamineSearcher.CreateSearchCriteria(String type, BooleanOperation defaultOperation) at Examine.LuceneEngine.Providers.BaseLuceneSearcher.CreateSearchCriteria(String type) at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetUmbracoMediaCacheValues(Int32 id)

I am unable to rebuild the Examine indexes at the backend (both ExternalIndexer and InternalIndexer have a locked error). The site still worked despite there errors for a while until this error came up and now the site is unresponsive:

2018-07-08 05:29:19,511 [P39896/D2/T184] ERROR Umbraco.Core.UmbracoApplicationBase - An unhandled exception occurred System.Exception: Exception while creating a value. ---> System.Data.SqlClient.SqlException: Connection Timeout Expired. The timeout period elapsed while attempting to consume the pre-login handshake acknowledgement. This could be because the pre-login handshake failed or the server was unable to respond back in time. The duration spent while attempting to connect to this server was - [Pre-Login] initialization=6183; handshake=40045; ---> System.ComponentModel.Win32Exception: The wait operation timed out --- End of inner exception stack trace --- at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling) at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource1 retry) at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1 retry) at System.Data.SqlClient.SqlConnection.Open() at Umbraco.Core.Persistence.FaultHandling.RetryPolicy.<>cDisplayClass20_0.0() at Umbraco.Core.Persistence.FaultHandling.RetryPolicy.ExecuteAction[TResult](Func1 func) at Umbraco.Core.Persistence.FaultHandling.RetryPolicy.ExecuteAction(Action action) at Umbraco.Core.Persistence.PetaPocoConnectionExtensions.OpenWithRetry(IDbConnection connection, RetryPolicy retryPolicy) at Umbraco.Core.Persistence.PetaPocoConnectionExtensions.OpenWithRetry(IDbConnection connection) at Umbraco.Core.Persistence.Database.OpenSharedConnection() at Umbraco.Core.Persistence.Database.BeginTransaction(IsolationLevel isolationLevel) at Umbraco.Core.Scoping.Scope.get_Database() at Umbraco.Core.Persistence.UnitOfWork.ScopeUnitOfWork.get_Database() at Umbraco.Core.Persistence.Repositories.MediaRepository.PerformGet(Int32 id) at Umbraco.Core.Cache.DefaultRepositoryCachePolicy2.Get(TId id, Func2 performGet, Func2 performGetAll) at Umbraco.Core.Persistence.Repositories.RepositoryBase2.Get(TId id) at Umbraco.Core.Services.MediaService.GetById(Int32 id) at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetUmbracoMediaCacheValues(Int32 id) at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.<>c__DisplayClass38_0.<GetCacheValues>b__0() at Umbraco.Core.Cache.DictionaryCacheProviderBase.<>c__DisplayClass10_0.<GetSafeLazy>b__0() --- End of inner exception stack trace --- at Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, CacheDependency dependency) at Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles) at Umbraco.Core.Cache.DeepCloneRuntimeCacheProvider.GetCacheItem(String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, String[] dependentFiles) at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetCacheValues(Int32 id, Func2 func) at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetUmbracoMedia(Int32 id) at Umbraco.Web.PublishedCache.XmlPublishedCache.PublishedMediaCache.GetById(UmbracoContext umbracoContext, Boolean preview, Int32 nodeId) at Umbraco.Web.PublishedCache.ContextualPublishedCache1.GetById(Boolean preview, Int32 contentId) at Umbraco.Web.PublishedContentQuery.DocumentById(Int32 id, ContextualPublishedCache cache, Object ifNotFound) at Umbraco.Web.PublishedContentQuery.Media(Int32 id) at Umbraco.Web.UmbracoHelper.Media(String id) at ASP._Page_Views_Partials_SectionAwards_cshtml.Execute() in \\websites\xxxxx\Views\Partials\SectionAwards.cshtml:line 17 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) at Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer) at System.Web.Mvc.HtmlHelper.RenderPartialInternal(String partialViewName, ViewDataDictionary viewData, Object model, TextWriter writer, ViewEngineCollection viewEngineCollection) at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData) at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model) at ASP._Page_Views_Partials_PageSectionRenderer_cshtml.Execute() in \\websites\xxx\Views\Partials\PageSectionRenderer.cshtml:line 2 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) at Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer) at System.Web.Mvc.HtmlHelper.RenderPartialInternal(String partialViewName, ViewDataDictionary viewData, Object model, TextWriter writer, ViewEngineCollection viewEngineCollection) at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData) at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model) at ASP._Page_Views_Partials_umbFooter_cshtml.Execute() in \\websites\xxxxxxx\Views\Partials\umbFooter.cshtml:line 46 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) at Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer) at System.Web.Mvc.HtmlHelper.RenderPartialInternal(String partialViewName, ViewDataDictionary viewData, Object model, TextWriter writer, ViewEngineCollection viewEngineCollection) at System.Web.Mvc.Html.RenderPartialExtensions.RenderPartial(HtmlHelper htmlHelper, String partialViewName) at ASP._Page_Views_Master_cshtml.Execute() in \\websites\xxxx\Views\Master.cshtml:line 13 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.WebPages.WebPageBase.<>c__DisplayClass3.<RenderPageCore>b__2(TextWriter writer) at System.Web.WebPages.HelperResult.WriteTo(TextWriter writer) at System.Web.WebPages.WebPageBase.Write(HelperResult result) at System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action1 body) at System.Web.WebPages.WebPageBase.PopContext() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) at Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer) at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList1 filters, ActionResult actionResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult1.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase1.End() at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) at System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase1.End() at System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) at System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase1.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.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid1.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.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Has anyone else had this issue and have any suggestions on how to fix it?