#! /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 in /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 attempt to 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.
#
# A config file may include domain names and any number of
# mailto: entries. For example:
#   mailto: ops@example.com, admin@example.com
#   remote1
#   remote2
#
# A domain will trigger a notification when first detected down and again
# when a restart is attempted.

use strict;
use warnings;

use File::Spec::Functions qw(rel2abs);
use File::Basename;
use Sys::Hostname qw(hostname);

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

# loads the config file into @servers and @mailRecipients.
sub loadConfig {
   my ($confName, $servers, $mailRecipients) = @_;

   if ( -f $confName ) {
      open my $CONF, '<', $confName or die "Could not read $confName: $!\n";
      while ( my $line = <$CONF> ) {
         chomp $line;
         $line =~ s/\r$//;
         next if $line =~ /^\s*#/;
         next if $line =~ /^\s*$/;

         if ( $line =~ /^\s*mailto\s*:\s*(.+?)\s*$/i ) {
            my @recipients = split /[\s,;]+/, $1;
            push @$mailRecipients, grep { length $_ } @recipients;
            next;
         }

         push @$servers, $line;
      }
      close $CONF;
   }
}

sub sendMail {
   my ($recipients, $subject, $message) = @_;

   return unless @$recipients;

   my %seen;
   my @to = grep { !$seen{$_}++ } @$recipients;

   if ( -x '/usr/sbin/sendmail' ) {
      open my $mailer, '|-', '/usr/sbin/sendmail', '-t'
         or die "Could not open /usr/sbin/sendmail: $!\n";
      print $mailer "To: " . join(', ', @to) . "\n";
      print $mailer "From: checkVirtuals@" . hostname() . "\n";
      print $mailer "Subject: $subject\n";
      print $mailer "Content-Type: text/plain; charset=UTF-8\n";
      print $mailer "\n";
      print $mailer $message;
      close $mailer or warn "sendmail returned an error while sending '$subject'\n";
      return;
   }

   if ( -x '/usr/bin/mail' ) {
      open my $mailer, '|-', '/usr/bin/mail', '-s', $subject, @to
         or die "Could not open /usr/bin/mail: $!\n";
      print $mailer $message;
      close $mailer or warn "mail returned an error while sending '$subject'\n";
      return;
   }

   warn "No mail transport found; skipping email notification for '$subject'\n";
}

# 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, \@mailRecipients );
die "No configuration file found at $configFile\n" unless @servers;

# find all running virtuals
my $output = `virsh list 2>/dev/null`;

# go through each virtual in @servers and make sure it is running
foreach my $server ( @servers ) {
   my $flagFile = "/tmp/$server.down";

   if ( $output =~ /(?:^|\s)$server(?:\s|$)/m ) {
      unlink $flagFile if -e $flagFile;
      next;
   }

   if ( -e $flagFile ) {
      print "$server has been down for a while, starting back up\n";

      my $subject = "Virtual domain $server still down; attempting restart";
      my $body = "The domain $server is still not running and the restart flag exists.\n";
      $body .= "Attempting restart with: /usr/bin/virsh start $server\n";
      $body .= "Checked at: " . scalar(localtime()) . "\n";
      sendMail( \@mailRecipients, $subject, $body );

      my $startStatus = system('/usr/bin/virsh start ' . $server);
      if ( $startStatus == 0 ) {
         unlink $flagFile;
      } else {
         warn "Failed to start $server with /usr/bin/virsh; leaving flag file in place\n";
      }
      next;
   }

   my $subject = "Virtual domain $server is down";
   my $body = "The domain $server is not running.\n";
   $body .= "Created flag file: $flagFile\n";
   $body .= "Checked at: " . scalar(localtime()) . "\n";
   sendMail( \@mailRecipients, $subject, $body );

   system('touch ' . quotemeta($flagFile));
}

1;