Re: strange bug with DBI, Sybase, sendmail and mod_perl

Jonathan Swartz
Wed, 06 Jan 2010 12:11:37 -0800

I tried this:

    ...
    do "/home/jswartz/projects/unchained-transaction/connect.pl";
    $dbh2 = dbconnect();
    $dbh1->{InactiveDestroy} = 1;
    $dbh2->{InactiveDestroy} = 1;
    open( MAIL, "|/usr/sbin/sendmail" ) || die "Can't open";
    ...

but the same bug still occurs.

I wondered, too, if database handles would get destroyed when thesendmail fork occurred. But as I understand it, open("|...") does afork and immediate exec(), so that Perl's destructors are not called.Someone correct me if I'm wrong.


Jon

On Jan 6, 2010, at 12:03 PM, m. allan noah wrote:

perhaps you should set InactiveDestroy true on your handle before you
open the pipe to sendmail?

allan

On Wed, Jan 6, 2010 at 2:50 PM, Jonathan Swartz <swa...@pobox.com>wrote:

This is one of the most bizarre and specific bugs I've ever seen.I've

minimized it as much as I can. Please bear with me. :)

Here is my mod_perl handler:

  package Handler;
  use DBI;
  use strict;
  use warnings;

  our ($dbh1, $dbh2);

  sub dbconnect {

return DBI->connect( 'DBI:Sybase:...', '...', '...',{ RaiseError => 1

} );
  }

  sub testdb {
      my ( $name, $dbh ) = @_;
      eval { $dbh->do("select 1") };
      print "$name - " . ($@ ? "error: $@" : "ok") . "\n";
  }

  sub handler {
      my ($r) = @_;

      # connect.pl contains one line: BEGIN { $Handler::dbh1 =
Handler::dbconnect() }
      do "/home/jswartz/projects/unchained-transaction/connect.pl";
      $dbh2 = dbconnect();

      open( MAIL, "|/usr/sbin/sendmail" ) || die "Can't open";
      testdb("dbh1", $dbh1);
      testdb("dbh2", $dbh2);
      close(MAIL);
      testdb("dbh1", $dbh1);
      testdb("dbh2", $dbh2);

      return 0;
  }

  1;

When I hit / on this server, it outputs:

  dbh1 - ok
  dbh2 - ok
  dbh1 - ok

dbh2 - error: DBD::Sybase::db do failed: OpenClient message:LAYER = (5)

ORIGIN = (3) SEVERITY = (5) NUMBER = (6)
  Server SANDBOX5, database

Message String: ct_results(): network packet layer: internal netlibrary

error: Net-Library operation terminated due to disconnect

OpenClient message: LAYER = (1) ORIGIN = (1) SEVERITY = (1)NUMBER = (50)

  Server SANDBOX5, database
  Message String: ct_cmd_drop(): user api layer: external error: The
connection has been marked dead.

That is, $dbh2 goes "bad" when the pipe to sendmail is closed. (?!)Note

that ping() still returns 1, I have to call do() to get the error.

Just about everything here is necessary to generate the bug. Inparticular,

I cannot generate the bug...

* If I move the code from connect.pl into the handler, even as astring eval

* If I remove the "BEGIN" from connect.pl
* If I replace sendmail with another program

* If I run this in a script outside of mod_perl - even a scriptthat forks


Obviously, I can change around our current code base to not hit this
particular condition, but that gives me no confidence that it won't
accidentally arise again, in this or another form.

Any advice on how to proceed appreciated!

Thanks
Jon

--------------

Using perl 5.10.1, DBI 1.609 , DBD::Sybase 1.09, Apache 2.2.14(latest

versions of all).

httpd.conf contains:

LoadModule perl_module /home/mercury/vendor/httpd/modules/mod_perl.so

ServerRoot         /home/jswartz/projects/unchained-transaction

DocumentRoot /home/jswartz/projects/unchained-transaction/htdocs

PidFile            logs/httpd.pid
TypesConfig        conf/mime.types

MinSpareServers      2
MaxSpareServers      3
StartServers         2
MaxClients           4
MaxRequestsPerChild  100

PerlPostConfigRequire
/home/jswartz/projects/unchained-transaction/conf/startup.pl
Listen 3010
<Location />
   SetHandler perl-script
   PerlHandler Handler
</Location>

Summary of my perl5 (revision 5 version 10 subversion 1)configuration:


 Platform:
   osname=linux, osvers=2.6.18-53.el5, archname=i686-linux

uname='linux hp-lt-171-rnebel.ensenda.com 2.6.18-53.el5 #1 smpwed oct 10

16:34:02 edt 2007 i686 i686 i386 gnulinux '
   config_args='-des -Uusethreads -Dprefix=/home/mercury/vendor/perl'
   hint=recommended, useposix=true, d_sigaction=define
   useithreads=undef, usemultiplicity=undef

useperlio=define, d_sfio=undef, uselargefiles=define,usesocks=undef

   use64bitint=undef, use64bitall=undef, uselongdouble=undef
   usemymalloc=n, bincompat5005=undef
 Compiler:
   cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_B\
ITS=64',
   optimize='-O2',
   cppflags='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include'
   ccversion='', gccversion='4.1.2 20070626 (Red Hat 4.1.2-14)',
gccosandvers=''
   intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234

d_longlong=define, longlongsize=8, d_longdbl=define,longdblsize=12

   ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
   alignbytes=4, prototype=define
 Linker and Libraries:
   ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
   libpth=/usr/local/lib /lib /usr/lib
   libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc
   perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
   libc=/lib/libc-2.5.so, so=so, useshrplib=false, libperl=libperl.a
   gnulibc_version='2.5'
 Dynamic Linking:
   dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
   cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib
-fstack-protector'


Characteristics of this binary (from libperl):
 Compile-time options: PERL_DONT_CREATE_GVSV PERL_MALLOC_WRAP
                       USE_LARGE_FILES USE_PERLIO
 Built under linux
 Compiled at Nov 20 2009 15:56:22




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"The truth is an offense, but not a sin"

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Re: strange bug with DBI, Sybase, sendmail and mod_perl