• Eric Blake's avatar
    backup: Document new XML for backups · 252958ee
    Eric Blake authored
    Prepare for new backup APIs by describing the XML that will represent
    a backup.  The XML resembles snapshots and checkpoints in being able
    to select actions for a set of disks, but has other differences.  It
    can support both push model (the hypervisor does the backup directly
    into the destination file) and pull model (the hypervisor exposes an
    access port for a third party to grab what is necessary).  Add
    testsuite coverage for some minimal uses of the XML.
    
    The <disk> element within <domainbackup> tries to model the same
    elements as a <disk> under <domain>, but sharing the RNG grammar
    proved to be hairy. That is in part because while <domain> use
    <source> to describe a host resource in use by the guest, a backup job
    is using a host resource that is not visible to the guest: a push
    backup action is instead describing a <target> (which ultimately could
    be a remote network resource, but for simplicity the RNG just
    validates a local file for now), and a pull backup action is instead
    describing a temporary local file <scratch> (which probably should not
    be a remote resource).  A future refactoring may thus introduce some
    way to parameterize RNG to accept <disk type='FOO'>...</disk> so that
    the name of the subelement can be <source> for domain, or <target> or
    <scratch> as needed for backups. Future patches may improve this area
    of code.
    Signed-off-by: Eric Blake's avatarEric Blake <[email protected]>
    Signed-off-by: Peter Krempa's avatarPeter Krempa <[email protected]>
    Reviewed-by: Daniel Berrange's avatarDaniel P. Berrangé <[email protected]>
    Reviewed-by: Jano Tomko's avatarJán Tomko <[email protected]>
    252958ee
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