Fw: [cpan #5135] fork disrupts the database connection 2.9002 and 2.9003

am 02.02.2004 18:35:06 von perl-list

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Distribution names: DBD-MySQL-2.9002 and DBD-mysql-2.9003
Perl versions: 5.8.0 and 5.8.1
Operating systems:

Linux cartman.network1.net 2.4.22-1.2115.nptl #1 Wed Oct 29 15:20:17 EST =
2003 i586
i586 i386 GNU/Linux

FreeBSD skipper.network1.net 4.8-RC FreeBSD 4.8-RC #0: Wed Mar 5 =
16:45:13 EST 2003
root@skipper.network1.net:/usr/obj/usr/src/sys/FNGi i386

After an initial select, and then a fork, the database connection still =
exists, but
is unusable. That is as specific as I can be...

Here is some example code that does not work under the above mentioned =
dbd versions,
but does work on dbd-mysql-2.1026:

#!/usr/bin/perl

my $db_host=3D'localhost';
my $db=3D'fngimon';
my $db_user=3D'';
my $db_pass=3D'';

use strict;
use DBI;
use POSIX ":sys_wait_h";

my $dbh=3D&db_connect($db_host,$db,$db_user,$db_pass);

while (1) {

my $sqlquery=3D"select id from interfaces order by rand() limit =
0, 5";
my $obj=3D&db_query($dbh,$sqlquery);
my $ntuples=3D$obj->rows();
my $debug=3D1;

while (my $ref =3D $obj->fetchrow_hashref()) {

my $interfaces_id=3D$ref->{'id'};
print "interfaces_id:$interfaces_id " if =
($debug);

&safefork;
}

print
"----------------------------------------------------------- -------------=
-----------------------------------------
\n";
}

############################################################ ##
# This subroutine forks the recv() so the script doesnt hang!#
############################################################ ##
sub safefork {

my $pid_;
my $return;
my %SIG;

$SIG{CHLD} =3D \&REAPER;
# do something that forks...
FORK: {
if ($pid_ =3D fork) {

# parent here
# child process pid is available in $pid_
return ($pid_);

} elsif (defined $pid_) { # $pid_ is zero here if =
defined

# child here
# Child code goes here!
# parent process pid is available with getppid

exit;

} elsif ($! =3D~ /No more process/) {

# EAGAIN, supposedly recoverable fork error
#sleep 5;
#redo FORK;
# Just exit:
exit;

} else {

# weird fork error
print ("Can't fork: $!\n");
exit;

}

}
} # end safefork sub-routine
############################################################ ############
# This subroutine is REAPER that prevents Zombies with his shiny scythe#
# This is necessary on sysv due to the way it handles signals #
############################################################ ############
sub REAPER {
my $child;
my %Kid_Status;
my %SIG;

# If a second child dies while in the signal handler caused by =
the
# first death, we won't get another signal. So must loop here =
else
# we will leave the unreaped child as a zombie. And the next =
time
# two children die we get another zombie. And so on.
while (($child =3D waitpid(-1,WNOHANG)) > 0) {
$Kid_Status{$child} =3D $?;
}
$SIG{CHLD} =3D \&REAPER; # still loathe sysV
} # end REAPER sub-routine
sub db_connect {

my ($db_host,$db,$db_user,$db_pass) =3D @_;
my ($dbh);
my ($note_connect)=3D0;

while (!$dbh) {

$dbh =3D DBI->connect("DBI:mysql:$db:$db_host", =
"$db_user", "$db_pass",
{PrintError =3D> 0});

if (!$dbh) {
$note_connect=3D1;
sleep 2;
}
}

if ($note_connect==1) {
$note_connect=3D0;
}

return ($dbh);

}
sub db_query {
my ($dbh,$sqlquery) =3D @_;
my ($obj) =3D $dbh->prepare("$sqlquery");
if (!$obj) {
exit;
}
if (!$obj->execute) {
exit;
}

return ($obj);

} # end db_query sub-routine;

Thank you,

Darren
First Network Group
Vice President Product Development
1-800-578-6381 x182
http://www.network1.net

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Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002and 2.9003

am 02.02.2004 19:53:32 von Rudy Lippan

On Mon, 2 Feb 2004, Darren L. Ankney wrote:

> Distribution names: DBD-MySQL-2.9002 and DBD-mysql-2.9003
> Perl versions: 5.8.0 and 5.8.1
> Operating systems:
>
> Linux cartman.network1.net 2.4.22-1.2115.nptl #1 Wed Oct 29 15:20:17 EST 2003 i586
> i586 i386 GNU/Linux
>
> FreeBSD skipper.network1.net 4.8-RC FreeBSD 4.8-RC #0: Wed Mar 5 16:45:13 EST 2003
> root@skipper.network1.net:/usr/obj/usr/src/sys/FNGi i386
>
> After an initial select, and then a fork, the database connection still
> exists, but is unusable. That is as specific as I can be...
>

You should not use a database handle across a fork (you might be able
to get away with it, but the behaviour is undefined).

> Here is some example code that does not work under the above mentioned
> dbd versions, but does work on dbd-mysql-2.1026:

That is probably because of the autoreconnect stuff in 2.1026 which is
turned off by default in later versions of DBD::mysql. I suggest that you
don't turn mysql_auto_reconnect on, however; You would be better off
creating a new connection in the child and using DBI's InactiveDestroy
attribute in the parrent.

Rudy

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Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002and 2.9003

am 02.02.2004 19:53:32 von Rudy Lippan

Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002 and 2.9003

am 02.02.2004 20:10:21 von perl-list

Rudy,

Regardless of whether i pass the database connection to the child or not the
database connection is still corrupted somehow...

In my example, the child is doing absolutely nothing but spawning and
exiting. No database operations are performed... Nor have i passed the
$dbh to the child. Yet still, after spawning the child, the database
connection no longer functions for the parent.

Thank you,

Darren
First Network Group
Vice President Product Development
1-800-578-6381 x182
http://www.network1.net

----- Original Message -----
From: "Rudy Lippan"
To: "Darren L. Ankney"
Cc:
Sent: Monday, February 02, 2004 1:53 PM
Subject: Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002
and 2.9003

> On Mon, 2 Feb 2004, Darren L. Ankney wrote:
>
> > Distribution names: DBD-MySQL-2.9002 and DBD-mysql-2.9003
> > Perl versions: 5.8.0 and 5.8.1
> > Operating systems:
> >
> > Linux cartman.network1.net 2.4.22-1.2115.nptl #1 Wed Oct 29 15:20:17 EST
2003 i586
> > i586 i386 GNU/Linux
> >
> > FreeBSD skipper.network1.net 4.8-RC FreeBSD 4.8-RC #0: Wed Mar 5
16:45:13 EST 2003
> > root@skipper.network1.net:/usr/obj/usr/src/sys/FNGi i386
> >
> > After an initial select, and then a fork, the database connection still
> > exists, but is unusable. That is as specific as I can be...
> >
>
> You should not use a database handle across a fork (you might be able
> to get away with it, but the behaviour is undefined).
>
> > Here is some example code that does not work under the above mentioned
> > dbd versions, but does work on dbd-mysql-2.1026:
>
> That is probably because of the autoreconnect stuff in 2.1026 which is
> turned off by default in later versions of DBD::mysql. I suggest that you
> don't turn mysql_auto_reconnect on, however; You would be better off
> creating a new connection in the child and using DBI's InactiveDestroy
> attribute in the parrent.
>
>
> Rudy
>
>
>
> --
> MySQL Perl Mailing List
> For list archives: http://lists.mysql.com/perl
> To unsubscribe:
http://lists.mysql.com/perl?unsub=sugiarto.Then@infotronik.c om
>

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Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002 and 2.9003

am 02.02.2004 20:10:21 von perl-list

Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002and 2.9003

am 02.02.2004 20:32:08 von Rudy Lippan

On Mon, 2 Feb 2004, Darren L. Ankney wrote:

> Rudy,
>
> Regardless of whether i pass the database connection to the child or not the
> database connection is still corrupted somehow...
>

I don't follow here. How do you not pass the database connection to the
child?

> In my example, the child is doing absolutely nothing but spawning and
> exiting. No database operations are performed... Nor have i passed the
> $dbh to the child. Yet still, after spawning the child, the database
> connection no longer functions for the parent.
>

You still need to set InactiveDestroy in the child (did I say parrent
before :) ) because when the child exists it will destroy its copy of the
$dbh and close the connection to the database.

Rudy

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Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002and 2.9003

am 02.02.2004 20:32:08 von Rudy Lippan

Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002 and 2.9003

am 02.02.2004 22:32:54 von perl-list

Rudy,

Thank you very much - setting InactiveDestroy did the trick... I set it in
the parent process...

I appologize for mistakenly thinking this was a bug :)

Thank you,

Darren
First Network Group
Vice President Product Development
1-800-578-6381 x182
http://www.network1.net

----- Original Message -----
From: "Rudy Lippan"
To: "Darren L. Ankney"
Cc:
Sent: Monday, February 02, 2004 2:32 PM
Subject: Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002
and 2.9003

> On Mon, 2 Feb 2004, Darren L. Ankney wrote:
>
> > Rudy,
> >
> > Regardless of whether i pass the database connection to the child or not
the
> > database connection is still corrupted somehow...
> >
>
> I don't follow here. How do you not pass the database connection to the
> child?
>
>
> > In my example, the child is doing absolutely nothing but spawning and
> > exiting. No database operations are performed... Nor have i passed the
> > $dbh to the child. Yet still, after spawning the child, the database
> > connection no longer functions for the parent.
> >
>
> You still need to set InactiveDestroy in the child (did I say parrent
> before :) ) because when the child exists it will destroy its copy of the
> $dbh and close the connection to the database.
>
>
> Rudy
>
>
> --
> MySQL Perl Mailing List
> For list archives: http://lists.mysql.com/perl
> To unsubscribe:
http://lists.mysql.com/perl?unsub=sugiarto.Then@infotronik.c om
>

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Re: Fw: [cpan #5135] fork disrupts the database connection 2.9002 and 2.9003

am 02.02.2004 22:32:54 von perl-list