在傀儡企业3.7中如何设置条件订阅？

Question

在我的puppet Enterprise3.7清单中，我有一个情况，我可以使用从我的服务到文件的有条件的“订阅”。我收到这个错误信息...

Invalid relationship: Service[openstack-cinder-api] { subscribe => File[/etc/cinder/nfs-shares.conf] }, because File[/etc/cinder/nfs-shares.conf] doesn't seem to be in the catalog

..。下面是导致上述错误的puppet代码。请注意，当条件$enabled_backends =~ /netapp-cinder/的计算结果为false时，就会出现错误。

class cinder (
... long list of parameters ...
) {
    if ( $enabled_backends =~ /netapp-cinder/ ) {
        file { '/etc/cinder/nfs-shares.conf':
            ensure  => file,
            path    => '/etc/cinder/nfs-shares.conf',
            owner   => cinder,
            group   => cinder,
            mode    => '0640',
            content => template('cinder/nfs-shares.conf.erb'),
        }
    }

    # long list of package and file resources 

    package {'qemu-kvm-rhev':
        ensure        => 'present',
        allow_virtual => false,
    } ->

    package { 'openstack-cinder':
        ensure => 'present',
        name   => 'openstack-cinder',
        before => [
            File['/etc/nova/nova.conf'],
        ],
    } ->

    package { 'python-cinderclient':
        ensure => 'present',
    } ->

    ... even more resource declarations ...

    service { 'openstack-cinder-api':
        ensure    => running,
        enable    => true,
        subscribe => [
            File['/etc/cinder/cinder.conf'],
            File['/etc/cinder/nfs-shares.conf'],
        ],
    } ->

    service { 'openstack-cinder-scheduler':
        ensure    => running,
        enable    => true,
        subscribe => [
            File['/etc/cinder/cinder.conf'],
            File['/etc/cinder/nfs-shares.conf'],
        ],
    } ->

    service { 'openstack-cinder-volume':
        ensure    => running,
        enable    => true,
        subscribe => [
            File['/etc/cinder/cinder.conf'],
            File['/etc/cinder/nfs-shares.conf'],
        ],
    }

    service { 'openstack-cinder-backup':
        ensure    => running,
        enable    => true,
        subscribe => [
            File['/etc/cinder/cinder.conf'],
            File['/etc/cinder/nfs-shares.conf'],
        ],
    } -> 

    ... more puppet code ...

有没有办法让订阅文件‘/etc/cinder/nfs-shares.conf’有条件呢？