Forking question
Hi, I'm working on a forking process and I need a way to check if any of the processes have failed and if they have restart them. Can anyone point me in the right direction to a tutorial or explanation of how to do this? Thanks in advance, Graeme
Re: Forking question
Hi Graeme, On Fri, 10 Aug 2012 10:10:10 +0100 G M iamnotregiste...@hotmail.com wrote: Hi, I'm working on a forking process and I need a way to check if any of the processes have failed and if they have restart them. Can anyone point me in the right direction to a tutorial or explanation of how to do this? How do you expect to know when a process has failed? Will it die in this case? If so, you'll receive a SIGCHLD signal and can trap it and handle it appropriately. There's some rudimentary coverage of that on http://perldoc.perl.org/perlipc.html (though I can warn you that the perl code is no longer considered idiomatic - see http://perl-begin.org/tutorials/bad-elements/ ), and you may also wish to look at https://metacpan.org/module/Parallel::ForkManager for a useful wrapper over the nitty-gritty details. If that's not what you want, then you'll have to explain. Regards, Shlomi Fish Thanks in advance, Graeme -- - Shlomi Fish http://www.shlomifish.org/ What Makes Software Apps High Quality - http://shlom.in/sw-quality The KGB used to torture their victims by having them look at scrolling XSLT code. Please reply to list if it's a mailing list post - http://shlom.in/reply . -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Forking question
Hi, I'm working on a forking process and I need a way to check if any of the processes have failed and if they have restart them. Can anyone point me in the right direction to a tutorial or explanation of how to do this? Or use a server framework like POE which manages forking for you. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Forking question
On 08/10/12 02:10, G M wrote: I'm working on a forking process and I need a way to check if any of the processes have failed and if they have restart them. Can anyone point me in the right direction to a tutorial or explanation of how to do this? Network Programming with Perl by Lincoln D. Stein covers forking (and threading): http://www.pearsonhighered.com/educator/product/Network-Programming-with-Perl/9780201615715.page David -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Forking question.
Good morning, afternoon, night,
I have been trying to work on a script that does forking. But
the script dies in the fork. Here is what I have:
I push some information about a server into an array.
snip
use POSIX sys_wait_h;
my $child_limit = 1;
my $child_pids = 0;
$SIG{CHLD} = \CHILD_COUNT($child_limit);
push @server_list, $href;
FORK:
{
while ( $#server_list -1 ) {
next if $child_pids $child_limit;
my $server_todo = pop @server_list;
if (my $pid = fork) {
# sleep 1; # failing due to bad
subroutine?
#do the parent
$child_pids++;
next;
}
elsif (defined $pid) {
# ok now the child.
do_stuff($server_todo); #subroutine
exit;
}
elsif ($! =~ /No more process/) {
print No more process ...sleeping\n;
sleep 5;
redo FORK;
}
else {
die Can't fork: $! \n;
}
}
}
sub CHILD_COUNT {
my $child_limit = @_;
my $child;
$child = waitpid(-1, WNOHANG);
while ( $child 0 ( $child_pids 0)) {
$child_pids-- if ( $child_pids 0);
$child = waitpid(-1,WNOHANG);
}
}
/snip
I get the error:
Not a subroutine reference at serverbackup.pl line 65.
Line 65 is the next if statement.
I am at a loss here. It seems that the more I read about this the
more I get confused.
Can anyone give me a hand with this? Or a push in the right direction?
It would be much appreciated.
Thanks
--chad
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Re: Forking question.
on Mon, 26 Aug 2002 14:15:02 GMT, [EMAIL PROTECTED] (Chad
Kellerman) wrote:
I have been trying to work on a script that does forking.
But the script dies in the fork. Here is what I have:
[...]
my $child_limit = 1;
my $child_pids = 0;
$SIG{CHLD} = \CHILD_COUNT($child_limit);
You can't have arguments here. This line should be:
$SIG{CHLD} = \CHILD_COUNT;
[...]
sub CHILD_COUNT {
my $child_limit = @_;
^
Remove this line, so you essentially work with the my-variable
$child_limit declared at file scope at the top of your program.
--
felix
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Re: Forking question.
you have:
my $child_limit = 1;
my $child_pids = 0;
$SIG{CHLD} = \CHILD_COUNT($child_limit);
the $child_limit thingy is ignored by Perl. this means when Perl calls your
CHIL_COUNT subroutine, the value of the variable $child_limit is not passed
in to your subroutine.
and then in the CHIL_COUNT subroutine, you have:
sub CHILD_COUNT {
my $child_limit = @_;
my $child_limit declares another variable, which happen to have the same
name as the $child_limit variable declared at the beginning of your program
but they are completely different thing. besides, i don't see you reference
$child_limit anywhere else inside your CHIL_COUNT subroutine, what's the
purpose of this $child_limit variable then?
my $child;
$child = waitpid(-1, WNOHANG);
while ( $child 0 ( $child_pids 0)) {
$child_pids-- if ( $child_pids 0);
$child = waitpid(-1,WNOHANG);
}
}
another thing:
while ( $#server_list -1 ) {
this might never be true.
if you try to archive:
1. given a list of servers
2. for each individual server, fork off a different child process(but stop
creating more child process once a certain number of them has been created)
to handle each server.
3. the parent will keep track the number of child process and wait for them
to finish.
then you might want to structure something like:
my @servers = ('server1','server2','server3');
my $child_max = 10; #-- allow 10 child process at once
my $child_process = 0;
$SIG{CHLD} = sub {
while((my $pid = waitpid(-1,WNOHANG)) 0){
$child_process--; #-- one less child process
print $pid finished\n;
}
};
while(@servers){
if($child_process $child_max){sleep(1);next;} #-- wait a little
my $pid = fork;
next unless(defined $pid); #-- fork success?
my $server = pop @servers;
if($pid){
#-- parent
$child_process++; #-- one more process
print $pid created.\n;
}else{
#-- child
handle_server($server);
print $server done. about to exit\n;
exit;
}
}
i hope that will help you a little.
david
Chad Kellerman wrote:
Good morning, afternoon, night,
I have been trying to work on a script that does forking. But
the script dies in the fork. Here is what I have:
I push some information about a server into an array.
snip
use POSIX sys_wait_h;
my $child_limit = 1;
my $child_pids = 0;
$SIG{CHLD} = \CHILD_COUNT($child_limit);
push @server_list, $href;
FORK:
{
while ( $#server_list -1 ) {
next if $child_pids $child_limit;
my $server_todo = pop @server_list;
if (my $pid = fork) {
# sleep 1; # failing due to bad
subroutine?
#do the parent
$child_pids++;
next;
}
elsif (defined $pid) {
# ok now the child.
do_stuff($server_todo); #subroutine
exit;
}
elsif ($! =~ /No more process/) {
print No more process ...sleeping\n;
sleep 5;
redo FORK;
}
else {
die Can't fork: $! \n;
}
}
}
sub CHILD_COUNT {
my $child_limit = @_;
my $child;
$child = waitpid(-1, WNOHANG);
while ( $child 0 ( $child_pids 0)) {
$child_pids-- if ( $child_pids 0);
$child = waitpid(-1,WNOHANG);
}
}
/snip
I get the error:
Not a subroutine reference at serverbackup.pl line 65.
Line 65 is the next if statement.
I am at a loss here. It seems that the more I read about this the
more I get confused.
Can anyone give me a hand with this? Or a push in the right direction?
It would be much appreciated.
Thanks
--chad
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Re: Forking question.
David wrote:
another thing:
while ( $#server_list -1 ) {
this might never be true.
i cut and paste too much! please ignore that!
david
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Re: Forking question.
on Mon, 26 Aug 2002 18:21:16 GMT, David wrote:
another thing:
while ( $#server_list -1 ) {
this might never be true.
It's true for as long as there are elements in @server_list.
It's equivalent to the (imho more readable)
while (@server_list) {
# do stuff (shifting or popping)
}
--
felix
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