drop tables crash

This is a weird one, I got running dropTables();

[2019-Jun-03 22:57:17.198] 30734 [/staff CNEc6DYxATl8owjH] [warning] "WApplication: WApplication::addMetaHeader() with no effect"
select "id", "version", "sysAuthInfo_id", "provider", "identity" from "sysAuthIdentity"  where ("sysAuthInfo_id" = $1) and ("provider" = $2)
/home/developer/projects/artecams/src/AppStaff.cpp:1536 dropping tables
/home/developer/projects/artecams/src/AppStaff.cpp:1540 

Thread 7 "artecams" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffe27fc700 (LWP 30743)]
0x00007ffff5bc652e in Wt::Dbo::Session::dropTables() () from /opt/Wt4/lib/libwtdbo.so.51
(gdb) bt
#0  0x00007ffff5bc652e in Wt::Dbo::Session::dropTables() () from /opt/Wt4/lib/libwtdbo.so.51
#1  0x0000555555d49332 in (anonymous namespace)::AdminWidget::drop_tables (this=0x7fffd00ad270) at /home/developer/projects/artecams/src/AppStaff.cpp:1542
#2  0x0000555555d4bb56 in std::__invoke_impl<void, void ((anonymous namespace)::AdminWidget::*&)(), (anonymous namespace)::AdminWidget*&> (

Here is the code;

1536   std::cout << __FILE__ << ":" << __LINE__ << " dropping tables" << std::endl;·
1537 ·
1538   Wt::Dbo::Transaction t(Rtm::AppBase::instance()-> session());·
1539 //  Rtm::AppBase::instance()-> session().execute("SET FOREIGN_KEY_CHECKS=0");·
1540   std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
1541 ·
1542   Rtm::AppBase::instance()-> session().dropTables();·
1543 //  Rtm::AppBase::instance()-> session().execute("SET FOREIGN_KEY_CHECKS=1");·
1544 ·
1545   std::cout << __FILE__ << ":" << __LINE__ << " done: tables dropped" << std::endl;·
1546 ·

Replies (19)

RE: drop tables crash - Added by Roel Standaert almost 4 years ago

I would guess that either Rtm::AppBase::instance() doesn't return a valid pointer, or session() doesn't return a valid session reference?

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

The session() is valid;

/home/developer/projects/artecams/src/AppStaff.cpp:1536 dropping tables
SELECT COUNT(1) as col0 FROM "sysUser"
/home/developer/projects/artecams/src/AppStaff.cpp:1548 7
/home/developer/projects/artecams/src/AppStaff.cpp:1551 
./doit.sh: line 15: 10394 Segmentation fault      (core dumped) ./artecams --config=wt_config.xml --approot="approot" --docroot="docroot;.,/images,/resources,/styles" --errroot="errroot" --http-listen 0.0.0.0:8077 --accesslog=/dev/null

From this code;

1534 void AdminWidget::drop_tables()·
1535 {·
1536   std::cout << __FILE__ << ":" << __LINE__ << " dropping tables" << std::endl;·
1537 ·
1538   Wt::Dbo::Transaction t(Rtm::AppBase::instance()-> session());·
1539   auto count =·
1540     Rtm::AppBase::instance()->·
1541       session().query<int>·
1542       (·
1543        "SELECT COUNT(1) FROM \"sysUser\""·
1544       )·
1545       .resultValue()·
1546       ;·
1547 ·
1548   std::cout << __FILE__ << ":" << __LINE__ << " " << count << std::endl;·
1549 ·
1550 //  Rtm::AppBase::instance()-> session().execute("SET FOREIGN_KEY_CHECKS=0");·                                                                                                                                                           
1551   std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
1552 · 
1553   Rtm::AppBase::instance()-> session().dropTables();·
1554 //  Rtm::AppBase::instance()-> session().execute("SET FOREIGN_KEY_CHECKS=1");·
1555 · 
1556   std::cout << __FILE__ << ":" << __LINE__ << " done: tables dropped" << std::endl;·
1557 ·
1558 }·

I don't even know what to begin looking at.

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

Here is what I have traced so far;

/home/developer/projects/artecams/src/AppStaff.cpp:1536 dropping tables
SELECT COUNT(1) as col0 FROM "sysUser"
/home/developer/projects/artecams/src/AppStaff.cpp:1548 7
/home/developer/projects/artecams/src/AppStaff.cpp:1551 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1066 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1070 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1080 
./doit.sh: line 15: 12093 Segmentation fault      (core dumped) ./artecams --config=wt_config.xml --approot="approot" --docroot="docroot;.,/images,/resources,/styles" --errroot="errroot" --http-listen 0.0.0.0:8077 --accesslog=/dev/null

1064 void Session::dropTables()·
1065 {·
1066 std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
1067 ·
1068   initSchema();·
1069 ·
1070 std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
1071 ·
1072   if (connectionPool_)·
1073   {·
1074     std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
1075 ·
1076     connectionPool_->prepareForDropTables();·
1077   }·
1078   else·
1079   {·
1080     std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
1081 ·
1082     connection_->prepareForDropTables();·                                                                                                                                                                                                
1083   }·
1084 ·
1085 std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
1086 ·

RE: drop tables crash - Added by Roel Standaert almost 4 years ago

So the session doesn't have a valid connection, maybe?

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

What about the "SELECT COUNT (1)..." immediately right above it?

RE: drop tables crash - Added by Roel Standaert almost 4 years ago

Yeah, I guess that the connection does not just disappear in the meantime... It looks like you don't use a debug build of Wt. Using a debug version could help pin down what is going wrong exactly (see the exact line number, check values of variables in the context of the segfault, etc.). So would using valgrind or address sanitizer.

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

How do I engage debugging?

RE: drop tables crash - Added by Roel Standaert almost 4 years ago

Normally you should have a debug build of Wt if you configure it with -DCMAKE_BUILD_TYPE=Debug, and link with the libwt...d.so or libwt...d.a libraries.

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

I don't see too much different here;

/home/developer/projects/artecams/src/AppStaff.cpp:1536 dropping tables
SELECT COUNT(1) as col0 FROM "sysUser"
/home/developer/projects/artecams/src/AppStaff.cpp:1548 7
/home/developer/projects/artecams/src/AppStaff.cpp:1551 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1066 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1070 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1080 

Thread 3 "artecams" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffe6832700 (LWP 16573)]
0x00007ffff5ab3a28 in Wt::Dbo::Session::dropTables() () from /opt/Wt4/lib/libwtdbod.so.51
(gdb) bt
#0  0x00007ffff5ab3a28 in Wt::Dbo::Session::dropTables() () at /opt/Wt4/lib/libwtdbod.so.51
#1  0x0000555555d4a122 in (anonymous namespace)::AdminWidget::drop_tables() (this=0x7fffd00ad2f0) at /home/developer/projects/artecams/src/AppStaff.cpp:1553
#2  0x0000555555d4c98a in std::__invoke_impl<void, void ((anonymous namespace)::AdminWidget::*&)(), (anonymous namespace)::AdminWidget*&>(std::__invoke_memfun_deref, void ((anonymous namespace)::AdminWidget::*&)((anonymous namespace)::AdminWidget* const), (anonymous namespace)::AdminWidget*&) (__f=@0x7fffd00adba0: (void ((anonymous namespace)::AdminWidget::*)((anonymous namespace)::AdminWidget * const)) 0x555555d49f26 <(anonymous namespace)::AdminWidget::drop_tables()>, __t=@0x7fffd00adbb0: 0x7fffd00ad2f0) at /usr/include/c++/7/bits/invoke.h:73
#3  0x0000555555d4c7aa in std::__invoke<void ((anonymous namespace)::AdminWidget::*&)(), (anonymous namespace)::AdminWidget*&>(void ((anonymous namespace)::AdminWidget::*&)((anonymous namespace)::AdminWidget* const), (anonymous namespace)::AdminWidget*&) (__fn=@0x7fffd00adba0: (void ((anonymous namespace)::AdminWidget::*)((anonymous namespace)::AdminWidget * const)) 0x555555d49f26 <(anonymous namespace)::AdminWidget::drop_tables()>, __args#0=@0x7fffd00adbb0: 0x7fffd00ad2f0) at /usr/include/c++/7/bits/invoke.h:95

With this;

 36 target_link_libraries(·
 37   artecams·
 38   wtd·
 39   wthttpd·
 40   wtdbod·
 41   wtdbosqlite3d·
 42   wtdbopostgresd·
 43   boost_system·
 44 )·

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

It's got to be a problem in my end... I'll re-audit what I've done.

RE: drop tables crash - Added by Roel Standaert almost 4 years ago

That's odd. I'd expect some more info if you really have a debug build of Wt. Is it stripped or something?

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

What do you mean stripped?

I re-compiled wt with the debug option, and then linked to the 'd' library files.

RE: drop tables crash - Added by Roel Standaert almost 4 years ago

Normally that happens if you make install/strip, or by adding the -s option. I don't assume you did that, but I'm not sure why you're not getting any more info than the function name and so file.

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

The connection is bad;

/home/developer/projects/artecams/src/AppStaff.cpp:1536 dropping tables
SELECT COUNT(1) as col0 FROM "sysUser"
/home/developer/projects/artecams/src/AppStaff.cpp:1548 1
/home/developer/projects/artecams/src/AppStaff.cpp:1551 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1066 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1070 
/home/serveradmin/projects/wt/src/Wt/Dbo/Session.C:1080 p:0
./doit.sh: line 15: 28718 Segmentation fault      (core dumped) ./artecams --config=wt_config.xml --approot="approot" --docroot="docroot;.,/images,/resources,/styles" --errroot="errroot" --http-listen 0.0.0.0:8077 --accesslog=/dev/null

   1064 void Session::dropTables()·
   1065 {·
   1066 std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
   1067 ·
   1068   initSchema();·
   1069 ·
   1070 std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
   1071 ·
   1072   if (connectionPool_)·
   1073   {·
   1074     std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
   1075 ·
   1076     connectionPool_->prepareForDropTables();·
   1077   }·
   1078   else·
   1079   {·
   1080     std::cout << __FILE__ << ":" << __LINE__ << " p:" << (void*)connection_.get() << std::endl;·
   1081 ·
   1082     connection_->prepareForDropTables();·
   1083   }·
   1084 ·
   1085 std::cout << __FILE__ << ":" << __LINE__ << " " << std::endl;·
   1086 ·

So, how could the connection be valid for the query, and be invalid for the drop-tables?

oey!

RE: drop tables crash - Added by lm at almost 4 years ago

The query you ran was select count(1) from ... ? Maybe the driver is really good at optimization and knows the answer without actually connecting to the database?

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

Yikes, that's a heck of a thought! This is just a 'normal' database, not a 'quantum' database, where it knows everything before I ask - lol

I don't know what's going on. The pointer there is clearly empty, perhaps wt should have an assert there... but, it's odd that I can run a query but not that other function.

I'm still exploring.

RE: drop tables crash - Added by Roel Standaert almost 4 years ago

I think I see it. prepareForDropTables() is directly called on the connection_, but the connection actually moves to the transaction object (and then moves back to the session when it's done).

This is because dropTables() is normally done outside of a transaction. I guess it should look at the transaction's connection instead of connection_ there.

In any case, doing dropTables() outside of a transaction should work.

RE: drop tables crash - Added by Roel Standaert almost 4 years ago

I pushed a commit that should make it possible to do dropTables() even if there already is an active transaction.

RE: drop tables crash - Added by Mark Petryk almost 4 years ago

That did it!

Thank you, Roel.

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