#! /usr/bin/env perl

# Script to start any virtuals which are down. Designed to be run
# from a cron job. The first pass, it will determine a virtual down
# and create a flag file file into /tmp/virtname.down
# on the next pass, it will see the virtual is still down and
# the flag file exists in /tmp. At that point, it will start the virtual
# and remove the file.
# on any pass, if it sees a virtual is up, it will remove the flag file
# if it exists.

# thus, length of time a virtual can be off is 2x periodicity of cron entry.
# we run it every 5 minutes, meaning the average down time is 7.5 min, and max
# is 10 min

# Looks for checkVirtuals.cfg in the same directory as the script.
# that file contains a list of virtuals found with virsh list
# any line with a pound sign in the first column will be ignored.

use strict;
use warnings;

my $configFileSuffix = '.cfg';
my @servers;

use File::Spec::Functions qw(rel2abs);
use File::Basename;

# loads the config file into $servers, which is a reference to an array
sub loadConfig {
   my ($confName, $servers ) = @_;
   if ( -f $confName ) {
      open CONF, "<$confName" or die "Could not read $confName: $!\n";
      @$servers = grep { ! m/^#/ } <CONF>;
      close CONF;
      chomp @$servers;
   }
}

# Figure out full path and name of script so we can find 
# config file
my ( $scriptname, $path ) = fileparse( $0 );
$path = rel2abs($path);
# remove any suffix, if it exists
if ( $scriptname =~ m/^(.*)\.[^.]+$/ ) { 
   $scriptname = $1;
}

my $configFile = $path . '/' . $scriptname . $configFileSuffix;

&loadConfig( $configFile , \@servers );
die "No configuration file found at $configFile\n" unless @servers;

#die "$configFile\n" . join( "\n", @servers ) . "\n";

# command used to start a virtual
my $virsh = '/usr/bin/virsh start ';
# find all running virtuals
my $output = `virsh list`;

# go through each virtual in @servers and make sure it is running
foreach my $server ( @servers ) {
   if ( $output =~ m/$server/ ) { # its running, so unlink the flag file if it exists
      unlink "/tmp/$server.down" if  -e "/tmp/$server.down";
   } else { # not running
      if ( -e "/tmp/$server.down" ) { # second iteration it has been down, so start it
         print "$server has been down for a while, starting back up\n";
         `$virsh $server`; 
         unlink "/tmp/$server.down";
      } else { # first time we've seen it, so just flag it
         `touch /tmp/$server.down`;
      }
   }
}

1;