hooking up gdb (was Re: [Zope-dev] More signal 11 restarts....)

[Andy Dustman]

On Wed, 2001-12-05 at 15:41, Matthew T. Kromer wrote:
> Leonardo Rochael Almeida wrote:
> 
> >We aren't getting any core files, even after setting ulimit correctly
> >(although we could be setting it uncorrectly. I'll look into that
> >further). Anyway, someone else in this list said that core dumps for
> >threaded apps in Linux were mostly useless, so we aren't investing much
> >energy in it anyway.
> >
> >With the short restart times we have, I'd prever a solution that didn't
> >involve keeping a dead site dead for too long (as in, debugging with
> >gdb). We are working in a ZEO scheme that would switch over the
> >accelerator to proxy another zeo client, but we are not there yet.
> >
> >It would be ideal if we could instruct python to grab the SIG11, invoke
> >gdb, get a C stacktrace for all threads and let Zope die in peace. If it
> >all happend in a few seconds, we will still keep the client happy.
> 
> Well largely, ALL I want is the backtrace -- and I'm wondering if I 
> could cobble something together that could get it.  The problem is it 
> needs to look at the symbol table, and I dont know how to get at that 
> via C -- ie, gdb doesnt have an interface that I know of that you can 
> link in to grab a stack trace and exit.

If you don't think a core dump is going to be useful, gdb isn't going to
be either.

I know I have gotten Zope to dump core before, and I think I did this
with -Z '', i.e. don't start a management process. Then you need some
other way to start Zope when it dies.

As for ZMySQLDA/MySQLdb, I do know that the MySQL client libraries will
crash if you try use the same connection more than once simultaneously
in two different threads. I have never quite been sure whether or not
there is some kind of locking in Zope to prevent threads from
simultaneously using two database connections, since I expect this would
cause problems on virtually all implementations.

-- 
Andy Dustman         PGP: 0x930B8AB6
    @       .net     http://dustman.net/andy
You can have my keys when you pry them from my dead, cold neurons.