Why do we get "An unexpected error occurred in Report Processing" in SSRS 2008? - reporting-services

Question

We often see this kind of errors in SSRS log file. This seems like internal error happening inside SSRS engine. How can we debug this ? We are not getting any other relevant information when report fails.
library!ReportServer_0-1!2864!09/09/2016-00:28:15:: w WARN:
Microsoft.ReportingServices.ReportProcessing.ReportProcessingException:
An unexpected error occurred in Report Processing. --->
System.Threading.ThreadAbortException: Thread was being aborted. at
Microsoft.Win32.Win32Native.SetFilePointerWin32(SafeFileHandle handle,
Int32 lo, Int32* hi, Int32 origin) at
Microsoft.Win32.Win32Native.SetFilePointer(SafeFileHandle handle,
Int64 offset, SeekOrigin origin, Int32& hr) at
System.IO.FileStream.SeekCore(Int64 offset, SeekOrigin origin) at
System.IO.FileStream.Seek(Int64 offset, SeekOrigin origin) at
Microsoft.ReportingServices.Library.PartitionFileStream.Seek(Int64
offset, SeekOrigin origin) at
Microsoft.ReportingServices.Library.MemoryUntilThresholdStream.Seek(Int64
offset, SeekOrigin origin) at
Microsoft.ReportingServices.Library.RSStream.Seek(Int64 offset,
SeekOrigin origin) at System.IO.BufferedStream.Seek(Int64 offset,
SeekOrigin origin) at
Microsoft.ReportingServices.Rendering.RPLProcessing.RPLReader.ReadElementProps(Int64
startOffset, RPLContext context, Byte& elementType) at
Microsoft.ReportingServices.Rendering.ExcelRenderer.Layout.LayoutEngine.RenderNewItem(IRowItemStruct
item, Int32 top, Int32 topRow, IExcelGenerator excel, String
pageContentKey, Dictionary2 sharedBorderCache, Dictionary2
sharedImageCache, Boolean& autosizableGrow, Boolean&
autosizableShrink) at
Microsoft.ReportingServices.Rendering.ExcelRenderer.Layout.LayoutEngine.RenderPageToExcel(IExcelGenerator
excel, String key, Dictionary2 sharedBorderCache, Dictionary2
sharedImageCache) at
Microsoft.ReportingServices.Rendering.ExcelRenderer.MainEngine.RenderRPLPage(RPLReport
report, Boolean headerInBody, Boolean suppressOutlines) at
Microsoft.ReportingServices.Rendering.ExcelRenderer.ExcelRenderer.Render(Report
report, NameValueCollection reportServerParameters,
NameValueCollection deviceInfo, NameValueCollection
clientCapabilities, Hashtable& renderProperties,
CreateAndRegisterStream createAndRegisterStream) at
Microsoft.ReportingServices.ReportProcessing.Execution.RenderReport.InvokeRenderer(IRenderingExtension
renderer, Report report, NameValueCollection reportServerParameters,
NameValueCollection deviceInfo, NameValueCollection
clientCapabilities, Hashtable& renderProperties,
CreateAndRegisterStream createAndRegisterStream) at
Microsoft.ReportingServices.ReportProcessing.Execution.RenderReport.Execute(IRenderingExtension
newRenderer) --- End of inner exception stack trace --- at
Microsoft.ReportingServices.ReportProcessing.Execution.RenderReport.Execute(IRenderingExtension
newRenderer) at
Microsoft.ReportingServices.ReportProcessing.ReportProcessing.RenderReport(DateTime
executionTimeStamp, ProcessingContext pc, RenderingContext rc,
IChunkFactory yukonCompiledDefinition) at
Microsoft.ReportingServices.Library.RenderLive.CallProcessingAndRendering(ProcessingContext
pc, RenderingContext rc, OnDemandProcessingResult& result) at
Microsoft.ReportingService
webserver!ReportServer_0-1!2864!09/09/2016-00:28:16:: e ERROR:
Throwing
Microsoft.ReportingServices.Diagnostics.Utilities.UnhandledHttpApplicationException:
,
Microsoft.ReportingServices.Diagnostics.Utilities.UnhandledHttpApplicationException:
The report server encountered an unhandled exception in
HttpApplication. ---> System.Web.HttpException: Request timed out.
--- End of inner exception stack trace ---;
--------- UPDATE ----------
I see new error in log as
library!WindowsService_0!e88!09/09/2016-17:09:45:: e ERROR: Throwing
Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerStorageException:
, An error occurred within the report server database. This may be
due to a connection failure, timeout or low disk condition within the
database.; dbcleanup!WindowsService_0!e88!09/09/2016-17:09:45:: e
ERROR: Error in CleanOrphanedSnapshots:
Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerStorageException:
An error occurred within the report server database. This may be due
to a connection failure, timeout or low disk condition within the
database. ---> System.Data.SqlClient.SqlException: Timeout expired.
The timeout period elapsed prior to completion of the operation or the
server is not responding.
library!WindowsService_0!e88!09/09/2016-17:09:45:: i INFO: Cleaned 0
batch records, 0 policies, 0 sessions, 0 cache entries, 0 snapshots, 0
chunks, 4 running jobs, 0 persisted streams, 0 segments, 0 segment
mappings, 0 edit sessions.
--------- UPDATE ----------
After updating all the timeout to 12hr and Put DO NOT TIMEOUT setting on SSRS site setting, we see diff error now.
So far we have checked execution log and it shows no error. Below error is found inside ssrs log file. Server has 32gb memory and we run on 64bit OS. This report sometimes is generated fine and its 200MB in size.
httpruntime!ReportServer_0-2!58dc!09/12/2016-23:26:45:: e ERROR:
Failed in BaseWorkerRequest::SendHttpResponse(bool),
exception=System.Runtime.InteropServices.COMException (0x800703E3):
The I/O operation has been aborted because of either a thread exit or
an application request. (Exception from HRESULT: 0x800703E3) at
Microsoft.ReportingServices.HostingInterfaces.IRsHttpPipeline.SendResponse(Void*
response, Boolean finalWrite, Boolean closeConn) at
ReportingServicesHttpRuntime.BaseWorkerRequest.SendHttpResponse(Boolean
finalFlush) library!ReportServer_0-2!58dc!09/12/2016-23:26:45:: e
ERROR: Throwing
Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerHttpRuntimeInternalException:
RsWorkerRequest::FlushResponse.,
Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerHttpRuntimeInternalException:
An internal or system error occurred in the HTTP Runtime object for
application domain ReportServer_REPCENTER_0-2-131182052998828671.
---> System.Runtime.InteropServices.COMException (0x800703E3): The I/O operation has been aborted because of either a thread exit or an
application request. (Exception from HRESULT: 0x800703E3) at
ReportingServicesHttpRuntime.BaseWorkerRequest.SendHttpResponse(Boolean
finalFlush) at
ReportingServicesHttpRuntime.RsWorkerRequest.FlushResponse(Boolean
finalFlush) --- End of inner exception stack trace ---;

Answer 1

Finally we have answer to this. Its the recyletime element inside "rsreportserver.config" file. By default this element value is set to 720 min (12 hr). This means from the time you start the SSRS service, it will recycle every 12 hr. Our service was started during mid night release this means it kept recycling everyday at noon. We have since update this value to 24 hr.
<RecycleTime>1440</RecycleTime>
<MaxAppDomainUnloadTime>60</MaxAppDomainUnloadTime>