~drizzle-trunk/drizzle/development

# -*- cperl -*-

# Copyright (C) 2006 MySQL AB

# 

# 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; version 2 of the License.

# 

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

# 

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

#

# This file is used from mysql-test-run.pl when choosing

# port numbers and directories to use for running mysqld.

#

use strict;

use Fcntl ':flock';

#

# Requested IDs are stored in a hash and released upon END.

#

my %mtr_unique_assigned_ids = ();

my $mtr_unique_pid;

BEGIN {

	$mtr_unique_pid = $$ unless defined $mtr_unique_pid;

}

END { 

	if($mtr_unique_pid == $$) {

		while(my ($id,$file) = each(%mtr_unique_assigned_ids)) {

			print "Autoreleasing $file:$id\n";

			mtr_release_unique_id($file, $id);

		}

	}

}

#

# Require a unique, numerical ID, given a file name (where all

# requested IDs are stored), a minimum and a maximum value.

#

# We use flock to implement locking for the ID file and ignore

# possible problems arising from lack of support for it on 

# some platforms (it should work on most, and the possible

# race condition would occur rarely). The proper solution for

# this is a daemon that manages IDs, of course.

#

# If no unique ID within the specified parameters can be 

# obtained, return undef.

#

sub mtr_require_unique_id($$$) {

	my $file = shift;

	my $min = shift;

	my $max = shift;

	my $ret = undef;

	my $changed = 0;

	my $can_use_ps = `ps -e | grep '^[ ]*$$ '`;

	if(eval("readlink '$file'") || eval("readlink '$file.sem'")) {

		die 'lock file is a symbolic link';

	}

	chmod 0777, "$file.sem";

	open SEM, ">", "$file.sem" or die "can't write to $file.sem";

	flock SEM, LOCK_EX or die "can't lock $file.sem";

	if(! -e $file) {

		open FILE, ">", $file or die "can't create $file";

		close FILE;

	}

	if(eval("readlink '$file'") || eval("readlink '$file.sem'")) {

		die 'lock file is a symbolic link';

	}

	chmod 0777, $file;

	open FILE, "+<", $file or die "can't open $file";

	select undef,undef,undef,0.2;

	seek FILE, 0, 0;

	my %taken = ();

	while(<FILE>) {

		chomp;

		my ($id, $pid) = split / /;

		$taken{$id} = $pid;

		if($can_use_ps) {

			my $res = `ps -e | grep '^[ ]*$pid '`;

			if(!$res) {

				print "Ignoring slot $id used by missing process $pid.\n";

				delete $taken{$id};

				++$changed;

			}

		}

	}

	for(my $i=$min; $i<=$max; ++$i) {

		if(! exists $taken{$i}) {

			$ret = $i;

			$taken{$i} = $$;

			++$changed;

			last;

		}

	}

	if($changed) {

		seek FILE, 0, 0;

		truncate FILE, 0 or die "can't truncate $file";

		for my $k (keys %taken) {

			print FILE $k . ' ' . $taken{$k} . "\n";

		}

	}

	close FILE;

	flock SEM, LOCK_UN or warn "can't unlock $file.sem";

	close SEM;

	$mtr_unique_assigned_ids{$ret} = $file if defined $ret;

	return $ret;

}

#

# Require a unique ID like above, but sleep if no ID can be

# obtained immediately.

#

sub mtr_require_unique_id_and_wait($$$) {

	my $ret = mtr_require_unique_id($_[0],$_[1],$_[2]);

	while(! defined $ret) {

		sleep 30;

		$ret = mtr_require_unique_id($_[0],$_[1],$_[2]);

		print "Waiting for unique id to become available...\n" unless $ret;

	}

	return $ret;

}

#

# Release a unique ID.

#

sub mtr_release_unique_id($$) {

	my $file = shift;

	my $myid = shift;

	if(eval("readlink '$file'") || eval("readlink '$file.sem'")) {

		die 'lock file is a symbolic link';

	}

	open SEM, ">", "$file.sem" or die "can't write to $file.sem";

	flock SEM, LOCK_EX or die "can't lock $file.sem";

	if(eval("readlink '$file'") || eval("readlink '$file.sem'")) {

		die 'lock file is a symbolic link';

	}

	if(! -e $file) {

		open FILE, ">", $file or die "can't create $file";

		close FILE;

	}

	open FILE, "+<", $file or die "can't open $file";

	select undef,undef,undef,0.2;

	seek FILE, 0, 0;

	my %taken = ();

	while(<FILE>) {

		chomp;

		my ($id, $pid) = split / /;

		$taken{$id} = $pid;

	}

	delete $taken{$myid};

	seek FILE, 0, 0;

	truncate FILE, 0 or die "can't truncate $file";

	for my $k (keys %taken) {

		print FILE $k . ' ' . $taken{$k} . "\n";

	}

	close FILE;

	flock SEM, LOCK_UN or warn "can't unlock $file.sem";

	close SEM;

	delete $mtr_unique_assigned_ids{$myid};

}

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