[interchange-cvs] interchange - ton modified code/UserTag/child-process.tag

[interchange-cvs at icdevgroup.org]

User:      ton
Date:      2008-12-14 10:06:04 GMT
Added:     code/UserTag child-process.tag
Log:
	Added new tag: child_process.

	This tag runs Interchange markup code in a forked child process.
	Useful for off-loading processes that take a relatively long
	time to complete.

	Thank you Jon for your kind assistance.

Revision  Changes    Path
1.1                  interchange/code/UserTag/child-process.tag


rev 1.1, prev_rev 1.0
Index: child-process.tag
===================================================================
# Copyright 2002-2007 Interchange Development Group and others
# 
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.  See the LICENSE file for details.
# 
# $Id: child-process.tag,v 1.1 2008-12-14 10:06:04 ton Exp $

UserTag child-process addAttr
UserTag child-process HasEndTag
UserTag child-process Version $Revision: 1.1 $
UserTag child-process Documentation <<EOD

=head1 NAME

child_process - Execute ITL code in a forked child process

=head1 SYNOPSIS

[child-process] ... ITL ... [/child-process]

=head1 DESCRIPTION

Runs Interchange markup code in a forked child process.
Useful for off-loading processes that take a relatively long time to complete.

Options are:

=over 4

=item filename

File name relative to catalog directory to file where output from forked
process should be stored.

=item notifyname

File name relative to catalog directory where a file of zero length will
be created if the file in option 'filename' is created successfully.

This empty file could be used for notification purposes, e.g. as an
indicator that the child process has delivered its output. When placed
in web docroot space one could poll for the existence of this file and
when it exists bounce to a page that will display the results.

=item umask

Octal umask for notification file.

=back

=head1 EXAMPLES

 This is the parent process.

 Child process starts here:<br>
 Child PID: [child-process filename="tmp/report_[time]%Y%m%d%H%M%S[/time].txt"]
 [query
     list=1
     sql="
         ... some long-running SQL query ...
     "
 ][sql-line]
 [/query]
 [/child-process]
 Child process ends here.

 Some more parent stuff....

=head1 AUTHORS

Ton Verhagen <tverhagen at alamerce.nl>

Jon Jensen <jon at endpoint.com>


=cut

EOD
UserTag child-process Routine <<EOR
sub {
	my ($opt, $body) = @_;
	use vars qw/ $Tag /;

	return unless defined($body) and length($body);

	my $pid;

	FORK: {
		if ($pid = fork) {
			# Parent
			# As parent we have no tasks to perform at this place
			# we only want to off-load 'heavy' processes to a child process
			# The main reason for this Usertag

			return $pid;
		}
		elsif (defined $pid) {
			# Child

			Vend::Server::reset_per_fork();

			my $output = interpolate_html($body, 1);
			if (defined($$output) and length($$output)) {
				my $filename = $opt->{filename};
				if (defined($filename) and length($filename)) {
					$filename = $Tag->filter('filesafe', $filename);
					my $status = $Tag->write_relative_file($filename, $$output);

					my $notifyname = $opt->{notifyname};
					if ($status and defined($notifyname) and length($notifyname)) {
						$notifyname = $Tag->filter('filesafe', $notifyname);
						$Tag->write_relative_file($notifyname, $opt, '');
					}

				}
			}

			exit;
		}
		elsif ($! =~ /No more process/) {
			# Supposedly recoverable fork error
			select(undef, undef, undef, 2.00);
			redo FORK;
		}
		else {
			# Weird fork error
			die "Can't fork: $!\n";
		}
	}
}
EOR