#!/usr/bin/perl

$SnapDir="/snapshots/mysql";
$SnapDev="/dev/asylum/mysql_snapshot";
$SnapSize="1G";
$MySQLDev="/dev/asylum/mysql";

$OnOff=$ARGV[0];
chomp $OnOff;

if ($ARGV[1] eq "-v" || $ARGV[1] eq "-v\n") {
  $Verbose="y";
  $MountParams="-v -t ext4 -o ro,noatime,nodiratime,noexec,nosuid,nodev,barrier=0";
  $UMountParams="-v";
} else {
  $Verbose="n";
  $MountParams="-t ext4 -o ro,noatime,nodiratime,noexec,nosuid,nodev,barrier=0";
  $UMountParams="";
}

if ($OnOff eq "on") {
  use DBI;
  $DB=DBI->connect("DBI:mysql:mysql" . ";mysql_read_default_file=/root/.my.cnf", root, $password)
    or die "Could not connect to MySQL\n";
  # flush and lock all tables
  $DB->do("flush tables with read lock;")
    or die "Can't flush and lock tables: ",$DB->errstr,"\n";
  # create the LVM snapshot device
    system ("lvcreate --size $SnapSize --snapshot --name $SnapDev $MySQLDev > /dev/null 2>&1") == 0
      or die "Can't create snapshot: $?\n";
  # unlock the tables so MySQL can continue serving clients
  # After this we don't have to talk to MySQL at all anymore.
  $DB->do("unlock tables");
  $DB->disconnect;
  # mount up the snapshot volume
  system ("mount $MountParams $SnapDev $SnapDir") == 0
    or die "Unable to mount snapshot: $?\n";
} elsif ($OnOff eq "off") {
  # Unmount the snapshot
  system ("umount $UMountParams $SnapDir") == 0
    or die "Can't unmount snapshot: $?\n";
  # Delete the snapshot volume
  system ("lvremove --force $SnapDev > /dev/null 2>&1") == 0
    or system ("lvremove --force $SnapDev > /dev/null") == 0
      or die "Can't remove the snapshot volume: $?\n";
} else {
  die "Invalid parameter used on command line.\n";
}