Answers request causes BI server to crash

I found an interesting bug in metalink. I wish there were more specifics as to how complex the report was. I just had a similar Assertion error yesterday which I tried to solve by increasing STACK size. However, it seems as it’s possible to crash BI server with longer reports.

When a custom report is executed on Windows the following error is received: –

Error Codes: OPR4ONWY:U9IM8TAC:OI2DL65P
State: HY000. Code: 10058. [NQODBC] [SQL_STATE: HY000] [nQSError: 10058] A general error has occurred. [nQSError: 46036] Internal Assertion: Condition FALSE, file .\NQThreads\SUGThread.cpp, line 515. (HY000)

However, on Linux the OBI Server crashes with this typical Stack Trace from the Core file generated: –

0 0xb427f9b2 in samem_details_800::ThreadAllocator<0>::Allocate
(this=0x86fcd00, Index=2) at threadallocator.cpp:443
443 { (gdb) bt
#0 0xb427f9b2 in samem_details_800::ThreadAllocator<0>::Allocate
(this=0x86fcd00, Index=2) at threadallocator.cpp:443 @ #1 0xb42784df in samem_details_800::ThreadAllocator<0>::allocate
(this=0x86fcd00, nBytes=20, nIndex=2,
pFile=0xb4a171dc “thirdpartysource/STLport-4.5/src/nqnodealloc.cpp”,
nLine=10) at threadallocator.cpp:966
#2 0xb4286098 in samem_details_800::Manager::Allocate (this=0xb429cac0, @ Bytes=20,
pFile=0xb4a171dc “thirdpartysource/STLport-4.5/src/nqnodealloc.cpp”,
nLine=10) at manager.cpp:469
#3 0xb4283dae in samem_800_allocate_dbg (Bytes=20, pFile=0xb4a171dc @ “thirdpartysource/STLport-4.5/src/nqnodealloc.cpp”, nLine=10)
at memoryallocator.cpp:160
#4 0xb49fbfb8 in NQNodeAlloc::allocate (__n=20) at @ thirdpartysource/STLport-4.5/src/nqnodealloc.cpp:10
#5 0xb721a1f3 in _SASSTL::allocator<_SASSTL::_Rb_tree_node
>::allocate (this=0x87f7bac, __n=1)
at thirdparty/include/stlport/stl/_alloc.h:372
#6 0xb721a02e in
_SASSTL::_STLP_alloc_proxy<_SASSTL::_Rb_tree_node*,
_SASSTL::_Rb_tree_node,
_SASSTL::allocator<_SASSTL::_Rb_tree_node > >::allocate @ (this=0x87f7bac, __n=1)
at thirdparty/include/stlport/stl/_alloc.h:514
#7 0xb72198c6 in _SASSTL::_Rb_tree, _SASSTL::less, @ _SASSTL::allocator >::_M_create_node (this=0x87f7bac, @ __x=@0xb0e23264)
at thirdparty/include/stlport/stl/_tree.h:243
#8 0xb673169d in _SASSTL::_Rb_tree, _SASSTL::less, @ _SASSTL::allocator >::_M_insert (this=0x87f7bac, __x_=0x0, @ __y_=0x8d895b8, __v=@0xb0e23264, __w_=0x0)
at thirdparty/include/stlport/stl/_tree.c:366
#9 0xb6730c6d in _SASSTL::_Rb_tree, _SASSTL::less, @ _SASSTL::allocator >::insert_unique (this=0x87f7bac, @ __v=@0xb0e23264)
at thirdparty/include/stlport/stl/_tree.c:412
#10 0xb6730499 in _SASSTL::set, _SASSTL::allocator >::insert @ (
this=0x87f7bac, __x=@0xb0e23264) at
thirdparty/include/stlport/stl/_set.h:137
#11 0xb672fe6b in RqNode::AddRqNodePtr (this=0x87f7b88, pRqNodePtr=0x8d999e8)
at server/Query/Optimizer/Request/Src/SQORRqNode.cpp:432
#12 0xb672e34e in SmartRqNodePtr (this=0x8d999e8, rhs=@0x8d995a0) at @ server/Query/Optimizer/Request/Src/SQORRqNode.cpp:55
#13 0xb66a7d17 in RqDerivedColumnReference (this=0x8d999b8, rhs=@0x8d99570, @ bNewIDs=false, bDeepCopy=true)
at server/Query/Optimizer/Request/Src/SQORRqExpr.cpp:1418
#14 0xb66a8898 in RqDerivedColumnReference::DeepCopy (this=0x8d99570, @ bNewIDs=false)
at server/Query/Optimizer/Request/Src/SQORRqExpr.cpp:1525
#15 0xb672e748 in RqNode (this=0x8d977b0, rhs=@0x8d97368, bNewIDs=false, @ bDeepCopy=true)
at server/Query/Optimizer/Request/Src/SQORRqNode.cpp:146
#16 0xb66a0d3c in RqExpr::RqExpr$base () at @ server/include/Query/Optimizer/Request/SQORRqNode.h:77
#17 0xb66d0f68 in RqExprCond::RqExprCond$base () at @ server/include/Query/Optimizer/Request/SQORRqList.h:33
#18 0xb66d6c58 in RqExprCondIsNull (this=0x8d977b0, rhs=@0x8d97368, @ bNewIDs=false, bDeepCopy=true)
at server/Query/Optimizer/Request/Src/SQORRqExprCond.cpp:1299
#19 0xb66d6e88 in RqExprCondIsNull::DeepCopy (this=0x8d97368, bNewIDs=false)
at server/Query/Optimizer/Request/Src/SQORRqExprCond.cpp:1342
#20 0xb672e748 in RqNode (this=0x8d8f878, rhs=@0x8d8f430, bNewIDs=false, @ bDeepCopy=true)
at server/Query/Optimizer/Request/Src/SQORRqNode.cpp:146
Cause
It appears that due to the complexity of the Expressions in the Answer Columns of the custom Report, the Expression Builder makes several recursive calls which eventually increases the Stack Size of the Thread until it reaches its maximum and it throws an Asertion Error.

On a Windows environment we have a check of the ‘LowStackCheck’ parameter which is not present in Linux and therefore it crashes the OBI Server giving a ‘sigsegv’ error.
Solution

Currently, there is no solution. The workaround is to re-design the report so that the Expressions are less complicated (e.g. Creating Measures that sum up at various combinations of Dimension Levels that allows the Users to avoid creating the complex Formulas in Answers and performs well)

This looks like a major change in the code is required to fix this type of behavior and therefore we will not be able to fix this until at least our 11.x release.

One thought on “Answers request causes BI server to crash”

  1. Thanks for this informative post, we have been facing the same issue , but could not understand the reason untill i read this blog.
    Can you please let me know where can i find the ‘LowStackCheck’ parameter.

    Regards
    Ravi

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