def relocate_vm(vm)
  #
  # Get our host name
  #
  our_host = vm.host_name                      # <-- Virtual Column
  #
  # Loop through the other hosts in our cluster
  #
  target_host = nil
  vm.ems_cluster.hosts.each do |this_host|      # <-- Two levels of Association
    next if this_host.name == our_host
    host_invalid = false
    this_host.vms.each do |this_vm|             # <-- Association
      if this_vm.tags(:server_role).first == our_server_role
        host_invalid = true
        break
      end
    end
    next if host_invalid
    #
    # If we get to here then no duplicate server_role VMs have been found
    # on this host
    #
    target_host = this_host
    break
  end
  if target_host.nil?
    raise "No suitable Host found to migrate VM #{vm.name} to"
  else
    $evm.log(:info, "Migrating VM #{vm.name} to host: #{target_host.name}")
    #
    # Migrate the VM to this host
    #
    vm.migrate(target_host)                     # <-- Method
  end
  return target_host.name
end

def send_email(group_name, vm_name, new_host)
  #
  # Find the group passed to us, and pull out the user emails
  #
  recipients = []
  group = $evm.vmdb('miq_group').find_by_description(group_name)
  group.users.each do |group_member|             # <-- Association
    recipients << group_member.email             # <-- Attribute
  end
  #
  # 'from' is the current logged-user who clicked the button
  #
  from = $evm.root['user'].email
  subject = "VM migration"
  body = "VM Name: #{vm_name} was live-migrated to Host: #{new_host}"
  body += " in accordance with anti-affinity rules"
  #
  # Send emails
  #
  recipients.each do |recipient|
    $evm.log(:info, "Sending email to <#{recipient}> from <#{from}> \
                     subject: <#{subject}>")
    $evm.execute(:send_email, recipient, from, subject, body)
  end
end

begin
  #----------------------------------------------------------------------------
  # Main code
  #----------------------------------------------------------------------------
  #
  # We've been called from a button on the VM object, so we know that
  # $evm.root['vm'] will be loaded
  #
  vm = $evm.root['vm']
  #
  # Find out this VM's server_role tag
  #
  our_server_role = vm.tags(:server_role).first
  unless our_server_role.blank?
    $evm.log(:info, "VM #{vm.name} has a server_role tag of: #{our_server_role}")
    #
    # Loop through the other VMs on the same host
    #
    vm.host.vms.each do |this_vm|             # <-- Two levels of Association
      next if this_vm.name == vm.name
      if this_vm.tags(:server_role).first == our_server_role
        $evm.log(:info, "VM #{this_vm.name} also has a server_role tag of: \
                                     #{our_server_role}, taking remedial action")
        new_host = relocate_vm(vm)
        send_email('EvmGroup-administrator', vm.name, new_host)
      end
    end
  end
  exit MIQ_OK

rescue => err
  $evm.log(:error, "[#{err}]\n#{err.backtrace.join("\n")}")
  exit MIQ_STOP
end