I am not sure how to go about even debugging this. Our host had an error on their server and our site went down. They appear to have fixed the issue on their side and not the entire site has an "HTTP Error 503. The service is unavailable." message. I cannot load any page even the back end. Nothing I do seems to make any difference.

This is the final message in the error log but this was hours ago and reloading the page does not add any additional errors to the log.

2018-12-02 13:46:03,170 [P21200/D2/T1] INFO  Umbraco.Core.CoreBootManager - Umbraco 7.7.8 application starting on HELA
 2018-12-02 13:46:03,170 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Determining hash of code files on disk
 2018-12-02 13:46:03,185 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Hash determined (took 9ms)
 2018-12-02 13:46:03,232 [P21200/D2/T1] INFO  Umbraco.Core.MainDom - Acquiring MainDom...
 2018-12-02 13:46:03,232 [P21200/D2/T1] INFO  Umbraco.Core.MainDom - Acquired MainDom.
 2018-12-02 13:46:03,232 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:46:03,295 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 63ms)
 2018-12-02 13:46:03,295 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IApplicationStartupHandler
 2018-12-02 13:46:03,295 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IApplicationStartupHandler (took 1ms)
 2018-12-02 13:46:03,326 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:46:03,326 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 0ms)
 2018-12-02 13:46:03,326 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving Umbraco.Core.PropertyEditors.IPropertyEditorValueConverter
 2018-12-02 13:46:03,326 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved Umbraco.Core.PropertyEditors.IPropertyEditorValueConverter (took 0ms)
 2018-12-02 13:46:03,326 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:46:03,326 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 0ms)
 2018-12-02 13:46:03,326 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving Umbraco.Core.PropertyEditors.IPropertyValueConverter
 2018-12-02 13:46:03,326 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved Umbraco.Core.PropertyEditors.IPropertyValueConverter (took 1ms)
 2018-12-02 13:46:03,342 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:46:03,342 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 0ms)
 2018-12-02 13:46:03,342 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving Umbraco.Web.Mvc.SurfaceController
 2018-12-02 13:46:03,342 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved Umbraco.Web.Mvc.SurfaceController (took 0ms)
 2018-12-02 13:46:03,342 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:46:03,342 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 0ms)
 2018-12-02 13:46:03,342 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving Umbraco.Web.WebApi.UmbracoApiController
 2018-12-02 13:46:03,342 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved Umbraco.Web.WebApi.UmbracoApiController (took 0ms)
 2018-12-02 13:46:05,185 [P21200/D2/T1] INFO  Umbraco.Core.DatabaseContext - CanConnect = True
 2018-12-02 13:46:05,373 [P21200/D2/T1] INFO  Umbraco.Web.Cache.CacheRefresherEventHandler - Initializing Umbraco internal event handlers for cache refreshing
 2018-12-02 13:46:05,404 [P21200/D2/T1] INFO  Umbraco.Forms.Core.Cache.CacheEventHandler - Initializing Umbraco Forms Events to trigger Cache Refreshers
 2018-12-02 13:46:06,842 [P21200/D2/T1] INFO  Umbraco.Web.Search.ExamineEvents - Initializing Examine and binding to business logic events
 2018-12-02 13:46:06,842 [P21200/D2/T1] INFO  Umbraco.Web.Search.ExamineEvents - Adding examine event handlers for index providers: 3
 2018-12-02 13:46:06,857 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:46:06,857 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 0ms)
 2018-12-02 13:46:06,857 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolving [Umbraco.Core.Persistence.Mappers.MapperForAttribute]Umbraco.Core.Persistence.Mappers.BaseMapper
 2018-12-02 13:46:06,857 [P21200/D2/T1] INFO  Umbraco.Core.PluginManager - Resolved [Umbraco.Core.Persistence.Mappers.MapperForAttribute]Umbraco.Core.Persistence.Mappers.BaseMapper (took 0ms)
 2018-12-02 13:46:06,967 [P21200/D2/T1] INFO  Umbraco.Core.CoreBootManager - Umbraco application startup complete (took 3895ms)
 2018-12-02 13:46:06,967 [P21200/D2/T1] INFO  Umbraco.Web.ExamineStartup - Forcing index InternalIndexSet to be unlocked since it was left in a locked state
 2018-12-02 13:46:06,982 [P21200/D2/T1] INFO  Umbraco.Web.ExamineStartup - Forcing index ExternalIndexSet to be unlocked since it was left in a locked state
 2018-12-02 13:46:07,326 [P21200/D2/T12] INFO  Umbraco.Core.Sync.ApplicationUrlHelper - New ApplicationUrl detected: [website_url]:80/umbraco
 2018-12-02 13:46:07,326 [P21200/D2/T12] INFO  Umbraco.Core.Sync.ApplicationUrlHelper - ApplicationUrl: [website_url]:80/umbraco (UmbracoModule request)
 2018-12-02 13:47:47,530 [P21200/D2/T5] INFO  umbraco.content - Load Xml from file...
 2018-12-02 13:47:47,546 [P21200/D2/T5] INFO  umbraco.content - Loaded Xml from file.
 2018-12-02 13:47:47,827 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:47:47,827 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 0ms)
 2018-12-02 13:47:47,827 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.ICacheRefresher
 2018-12-02 13:47:47,827 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.ICacheRefresher (took 0ms)
 2018-12-02 13:47:50,296 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:47:50,296 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 0ms)
 2018-12-02 13:47:50,296 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolving Umbraco.Core.PropertyEditors.IParameterEditor
 2018-12-02 13:47:50,296 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolved Umbraco.Core.PropertyEditors.IParameterEditor (took 0ms)
 2018-12-02 13:47:52,780 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolving umbraco.interfaces.IDiscoverable
 2018-12-02 13:47:52,780 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolved umbraco.interfaces.IDiscoverable (took 0ms)
 2018-12-02 13:47:52,780 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolving Umbraco.Core.Deploy.IServiceConnector
 2018-12-02 13:47:52,780 [P21200/D2/T5] INFO  Umbraco.Core.PluginManager - Resolved Umbraco.Core.Deploy.IServiceConnector (took 0ms)
 2018-12-02 13:47:53,717 [P21200/D2/T5] INFO  Umbraco.Core.Publishing.PublishingStrategy - Content 'Adverts Sidebar' with Id '10633' has been published.
  2018-12-02 13:47:55,999 [P21200/D2/T11] ERROR Umbraco.Core.UmbracoApplicationBase - Unhandled exception in AppDomain (terminating)
System.IndexOutOfRangeException: Index of bound 0
   at Lucene.Net.Util.BitVector.GetAndSet(Int32 bit)
   at Lucene.Net.Index.SegmentReader.DoDelete(Int32 docNum)
   at Lucene.Net.Index.IndexReader.DeleteDocument(Int32 docNum)
   at Lucene.Net.Index.DocumentsWriter.ApplyDeletes(IndexReader reader, Int32 docIDStart)
   at Lucene.Net.Index.DocumentsWriter.ApplyDeletes(SegmentInfos infos)
   at Lucene.Net.Index.IndexWriter.ApplyDeletes()
   at Lucene.Net.Index.IndexWriter.DoFlushInternal(Boolean flushDocStores, Boolean flushDeletes)
   at Lucene.Net.Index.IndexWriter.DoFlush(Boolean flushDocStores, Boolean flushDeletes)
   at Lucene.Net.Index.IndexWriter.PrepareCommit(IDictionary`2 commitUserData, Boolean internal_Renamed)
   at Lucene.Net.Index.IndexWriter.Commit(IDictionary`2 commitUserData)
   at Examine.LuceneEngine.Providers.LuceneIndexer.IndexCommiter.TimerRelease()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.TimerQueueTimer.CallCallback()
   at System.Threading.TimerQueueTimer.Fire()
   at System.Threading.TimerQueue.FireNextTimers()
 2018-12-02 13:47:55,999 [P21200/D2/T12] ERROR Umbraco.Core.UmbracoApplicationBase - Unhandled exception in AppDomain (terminating)
System.IndexOutOfRangeException: Index of bound 0
   at Lucene.Net.Util.BitVector.GetAndSet(Int32 bit)
   at Lucene.Net.Index.SegmentReader.DoDelete(Int32 docNum)
   at Lucene.Net.Index.IndexReader.DeleteDocument(Int32 docNum)
   at Lucene.Net.Index.DocumentsWriter.ApplyDeletes(IndexReader reader, Int32 docIDStart)
   at Lucene.Net.Index.DocumentsWriter.ApplyDeletes(SegmentInfos infos)
   at Lucene.Net.Index.IndexWriter.ApplyDeletes()
   at Lucene.Net.Index.IndexWriter.DoFlushInternal(Boolean flushDocStores, Boolean flushDeletes)
   at Lucene.Net.Index.IndexWriter.DoFlush(Boolean flushDocStores, Boolean flushDeletes)
   at Lucene.Net.Index.IndexWriter.PrepareCommit(IDictionary`2 commitUserData, Boolean internal_Renamed)
   at Lucene.Net.Index.IndexWriter.Commit(IDictionary`2 commitUserData)
   at Examine.LuceneEngine.Providers.LuceneIndexer.IndexCommiter.TimerRelease()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.TimerQueueTimer.CallCallback()
   at System.Threading.TimerQueueTimer.Fire()
   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()