create_multipath.pl - Essentially this script takes the the iscsi target information and creates and friendly name multipath.conf configuration based upon the iscsi volume name.

create_multipath.pl

#!/usr/bin/perl -w

# This is not my script, it is one that I've used for a very long time but don't
# know whom the original author is. Essentally this script takes the the iscsi
# target information and creates and friendly name multipath.conf configuration
# based upon the iscsi volume name. It takes the end string of iscsi target after
# the last "-" to create a frendly dev mapper path. I would like to simplify it
# and re-write it in python but but I haven't had the time to do so and my perl
# skill are limited, so the perl version is maitained with what little changes
# I've made and what limited knowledge of perl I have.
#
# To use the script you simply login your iscsi target volumes and execute the
# script, if the config passed validation it is copied to /etc/multipath.conf
# afterwhich you need to either restart multipathd service or refresh multipath
# configuration with 'multipath -r'. Make sure you have perl libary
# perl-Data-Dump installed or it will fail to work.
#
# Improvements and requests for simplfication are encouraged.
#
# Last known modification: October 8, 2020

use strict;
use Data::Dumper;

my $disk_map = {};
my $last = {};
my $customer_map = {};
my @tmp = ();
my $cmd = "iscsiadm -m session -P 3";
my $customer;
if ($ARGV[0]) {
  print "Setting \$customer to $ARGV[0]\n";
  $customer = sprintf("%06d", $ARGV[0]);
}

my $PID=$$;
my $old_PID='';

open ( RESULT, ">", "/tmp/multipath.$PID" )
		or die "Cannot open /tmp/multipath.$PID\n";

sub check_pid()
{

	open ( PIDFILE, "+<", "/var/run/create_multipath")
		or die "Cannot open /var/run/create_multipath\n";

	while (<PIDFILE>)
	{
		if ( $_ )
		{
		my $proc=$_;
		if ( -d "/proc/$proc" )
			{
			close PIDFILE;
			return 1;
			}
		else
			{
			close PIDFILE;
			return 0;
			}
		}
	}

}

if ( ! -f "/var/run/create_multipath")
	{
	open ( PIDFILE, ">", "/var/run/create_multipath")
		or die "Cannot open /var/run/create_multipath\n";
	close PIDFILE;
	}

while ( check_pid )
	{
	print "$PID sleeping 5\n";
	sleep 5;
	}

open ( PIDFILE, ">", "/var/run/create_multipath")
	or die "Cannot open /var/run/create_multipath\n";

print PIDFILE $PID;
close PIDFILE;

print "$PID Its me!\n";

# print multipath.conf headers

print RESULT "#
defaults {
        user_friendly_names yes
        polling_interval 10
        path_selector \"round-robin 0\"
        path_grouping_policy multibus
        path_checker tur
        rr_min_io_rq 10
        max_fds 8192
        rr_weight priorities
        failback immediate
        features 0
        no_path_retry queue
}
multipaths {\n";

my $good;
do {
	# If I'm not specifically adding a Customer's Volume, assume the result is good
	if (! defined $customer ) {
		$good = 1;
	}
	else
	{
		$good = 0;
	}
	print "Running $cmd\n";
	open ISCSI, "$cmd |";
	while (<ISCSI>)
	{
		#Target: iqn.2001-05.com.equallogic:0-8a0906-80995e803-c8b0000009e4b71b-kvmt43
		#			Attached scsi disk sdjg		State: running
		#			Attached scsi disk sdjj		State: running
		if ($_ =~ m/^Target:\s+(\S+)/)
		{
			$last->{'target'} = $1;
			@tmp = split("-",$last->{'target'});
	                $last->{'customerID'} = @tmp[@tmp - 1];
			print "Found volume for $last->{'customerID'}\n";
		}
		if ($_ =~ m/^\s+Attached scsi disk (\S+)/)
		{
			$disk_map->{$1}->{'Target'} = $last->{'target'};
			$disk_map->{$1}->{'customerID'} = $last->{'customerID'};
			print "$1 = $disk_map->{$1}->{'customerID'} = $disk_map->{$1}->{'Target'}\n";
			$good = 1 if (defined $customer && $last->{'customerID'} == $customer);
		}
	}
	close ISCSI;
	print "Could not find volume for account $customer\n" if ($good == 0 && defined $customer);
	sleep 1 if ($good == 0);
} until ($good == 1);

do {
	if (defined $customer) {
		$good = 0;
	}
	else
	{
		$good = 1;
	}
	print "Running multipath -l\n";
	open MULTIPATH, "multipath -l |";
	while (<MULTIPATH>)
	{
		#eq-057 (36090a038805e097b1bb7f40200007097) dm-162 EQLOGIC,100E-00
		#[size=30G][features=0][hwhandler=0][rw]
		#\_ round-robin 0 [prio=0][active]
		# \_ 848:0:0:0  sdjc 8:352   [active][undef]
	
		if ($_ =~ m/\(([^\)]+)\)/)
		{
			$last->{'WWID'} = $1;
		}
		if ($_ =~ m/\d+:\d+:\d+:\d+\s+(\S+)/)
		{
			$disk_map->{$1}->{'WWID'} = $last->{'WWID'};
			print "$1 = $disk_map->{$1}->{'WWID'}\n";
			$good = 1;
		}
	}
	close MULTIPATH;
	#print Dumper($disk_map);


	for my $disk (keys %$disk_map)
	{
		#$customer_map->{$disk_map->{$disk}->{'customerID'}}->{'customerID'} = $disk_map->{$disk}->{'customerID'};
		if (! defined $disk_map->{$disk}->{'WWID'} || $disk_map->{$disk}->{'WWID'} =~ m/^$/) {
			print "\$disk_map->{\$disk}->{'WWID'} ($disk) Is not defined\n";
		}
		$customer_map->{$disk_map->{$disk}->{'customerID'}}->{'WWID'} = $disk_map->{$disk}->{'WWID'};
		$customer_map->{$disk_map->{$disk}->{'customerID'}}->{'Target'} = $disk_map->{$disk}->{'Target'};
	}
	
	for my $customerID (sort keys %$customer_map)
	{
		if (! defined $customer_map->{$customerID}->{'WWID'}) {
			print STDERR "Missing CustomerID->WWID relationship. Trying again\n";
			sleep 1;
			$good=0;
		}
		else
		{
			print RESULT "\tmultipath {
\t\twwid\t\t$customer_map->{$customerID}->{'WWID'}
\t\tfailback\t\timmediate
\t\trr_min_io\t\t1000
\t\talias\t\t\t$customerID
\t}
";
		}
	}
	print "Something went wrong with multipath -l output." if (! $good);
	sleep 1 if (! $good);
} until ($good);

# print closing curly

print RESULT "}\n";

close RESULT;

`cp /tmp/multipath.$PID /etc/multipath.conf`;

unlink "/tmp/multipath.$PID";