Scheduled Refresh sometimes failing at "Streaming model to Analysis Server." / rsInternalError

[manu1]

Our Report Server started to develop some strange behavior with scheduled refreshes.

Most of the time and at the moment these refreshes work correctly. But a few days back nearly no refreshes were working for more than a day. At times we even had some memory dumps.

The errors we get in the “RSPowerBI….log” do look as following:

Spoiler

2020-11-12 19:45:09.1846|INFO|33|Handling event with data: TimeEntered: 12.11.2020 18:45:00, Type: Event, SessionId: 8ae0c18c-cb05-4d0f-8078-baa96625a22f, EventType: DataModelRefresh
2020-11-12 19:45:09.2002|INFO|33|Processing Data Model Refresh: SessionId: 8ae0c18c-cb05-4d0f-8078-baa96625a22f, Status: Starting Data Refresh.
2020-11-12 19:45:09.2002|INFO|33|Processing Data Model Refresh: SessionId: 8ae0c18c-cb05-4d0f-8078-baa96625a22f, Status: Starting Retrieving PBIX AsDatabaseInfo.
2020-11-12 19:45:09.2314|INFO|33|Processing Data Model Refresh: SessionId: 8ae0c18c-cb05-4d0f-8078-baa96625a22f, Status: Starting Verifying all the data sources are embedded.
2020-11-12 19:45:09.2314|INFO|33|Processing Data Model Refresh: SessionId: 8ae0c18c-cb05-4d0f-8078-baa96625a22f, Status: Starting Verifying connection strings are valid.
2020-11-12 19:45:09.2471|INFO|33|Processing Data Model Refresh: SessionId: 8ae0c18c-cb05-4d0f-8078-baa96625a22f, Status: Starting Streaming model to Analysis Server.
2020-11-12 19:45:09.7158|ERROR|33|Error Processing Data Model Refresh: SessionId: 8ae0c18c-cb05-4d0f-8078-baa96625a22f, Status: Error Failed Streaming model to Analysis Server, Exception System.InvalidOperationException: Internal connection fatal error. Error state: 18
at System.Data.SqlClient.TdsParserStateObject.TryProcessHeader()
at System.Data.SqlClient.TdsParserStateObject.TryPrepareBuffer()
at System.Data.SqlClient.TdsParserStateObject.TryReadByteArray(Byte[] buff, Int32 offset, Int32 len, Int32& totalRead)
at System.Data.SqlClient.TdsParser.TrySkipPlpValue(UInt64 cb, TdsParserStateObject stateObj, UInt64& totalBytesSkipped)
at System.Data.SqlClient.TdsParser.TrySkipValue(SqlMetaDataPriv md, Int32 columnOrdinal, TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParser.TrySkipRow(_SqlMetaDataSet columns, Int32 startCol, TdsParserStateObject stateObj)
at System.Data.SqlClient.SqlDataReader.TryCleanPartialRead()
at System.Data.SqlClient.SqlDataReader.TryCloseInternal(Boolean closeReader)
at System.Data.SqlClient.SqlDataReader.Close()
at System.Data.Common.DbDataReader.Dispose(Boolean disposing)
at Microsoft.ReportingServices.CatalogAccess.Streams.VarbinaryReadableStream.Dispose(Boolean disposing)
at System.IO.Stream.Close()
at Microsoft.PowerBI.ReportServer.WebHost.EventHandler.AnalysisServicesDataRefresh.LoadModel(AsDatabaseInfo asDatabaseInfo)
at Microsoft.PowerBI.ReportServer.WebHost.EventHandler.DataRefreshScope.<>c__DisplayClass34_0.<ExecuteActionWithLogging>b__0()
at Microsoft.PowerBI.ReportServer.WebHost.EventHandler.DataRefreshScope.<ExecuteFuncWithLogging>d__33`1.MoveNext()
2020-11-12 19:45:09.7314|ERROR|33|Error Processing Data Model Refresh: SessionId: 8ae0c18c-cb05-4d0f-8078-baa96625a22f, Status: Error Failed Data Refresh, Exception System.InvalidOperationException: Internal connection fatal error. Error state: 18
at Microsoft.PowerBI.ReportServer.WebHost.EventHandler.DataRefreshScope.ExecuteActionWithLogging(Action methodToExecute, String description, String localizedDescription, String messageInFailure, RefreshInfo refreshInfo, DataAccessors dataAccessors, ReportEventType operation, Boolean isDataRetrieval, Boolean showInExecutionLog, Boolean sendToTelemetry)
at Microsoft.PowerBI.ReportServer.WebHost.EventHandler.AnalysisServicesDataRefresh.RefreshData(RefreshInfo refreshInfo)
at Microsoft.PowerBI.ReportServer.WebHost.EventHandler.DataRefreshScope.<>c__DisplayClass34_0.<ExecuteActionWithLogging>b__0()
at Microsoft.PowerBI.ReportServer.WebHost.EventHandler.DataRefreshScope.<ExecuteFuncWithLogging>d__33`1.MoveNext()
2020-11-12 19:45:19.7628|INFO|32|Started clean up of embedded models
2020-11-12 19:45:19.7628|INFO|32|Finished clean up of 0 embedded models

The server has plenty of cpu and memory resources. Memory is never higher than 50%, cpu normal at 5-10% and peaks from time to time to 80-98% for the duration of a scheduled refresh (5-20s)

msmdsrv.ini is at default settings

msmdsrv.log shows no errors at all.

Sometimes these errors also occur at night, when general workload on our system is at its lowest.

We are at Version 15.0.1103.234 and now prepairing to update to 15.0.1104.239

By now I have run out of ideas to search for the source of the problem.

Any suggestions where I should set my focus?