Got 4 mailbox servers and have had this twice now. Indexes fail and DBs switch. Reboot of mailbox server solves issue.
(and yes Content Submitters group is set up)
Error in event log is:-
The indexing of mailbox database MDB17 encountered an unexpected exception. Error details: Microsoft.Exchange.Search.Core.Abstraction.OperationFailedException: The component operation has failed. ---> Microsoft.Exchange.Search.Core.Abstraction.OperationFailedException:
The component operation has failed. ---> Microsoft.Exchange.Search.Fast.FastDocumentTimeoutException: The Content Submission Service returned failure for the document: Document timeout expired
. ---> System.TimeoutException: Document timeout expired
--- End of inner exception stack trace ---
at Microsoft.Exchange.Search.Fast.FastFeeder.EndSubmitDocument(IAsyncResult asyncResult)
at Microsoft.Exchange.Search.Mdb.RetryFeeder.DocumentCompleteCallback(IAsyncResult asyncResult)
--- End of inner exception stack trace ---
at Microsoft.Exchange.Search.Core.Common.Executable.EndExecute(IAsyncResult asyncResult)
at Microsoft.Exchange.Search.Engine.SearchFeedingController.ExecuteComplete(IAsyncResult asyncResult)
--- End of inner exception stack trace ---
at Microsoft.Exchange.Search.Core.Common.Executable.EndExecute(IAsyncResult asyncResult)
at Microsoft.Exchange.Search.Engine.SearchRootController.ExecuteComplete(IAsyncResult asyncResult)