---
features:
  - |
    The identifier ``compressed`` has been added to the list of supported
    container formats.  The intent is that this format identifier will be used
    for any compressed file archive format (for example, gzip or rar) that is
    not otherwise covered by the existing container format identifiers.

    As with all container formats, Glance does not verify that the data payload
    of an image is actually in that format.  Further, you should not expect
    other OpenStack services to be able to handle arbitrary compressed file
    formats.  Consult the documentation of any services that will consume your
    image for details.
upgrade:
  - |
    The identifier ``compressed`` has been added to the list of supported
    container formats.  The intent is that this format identifier will be used
    for any compressed file archive format (for example, gzip or rar) that is
    not otherwise covered by the existing container format identifiers.

    The ``compressed`` container format was added in support of the Cinder
    (Block Storage Service) feature `Leverage compression accelerator
    <http://specs.openstack.org/openstack/cinder-specs/specs/train/leverage-compression-accelerator.html>`_.
    You may expect that Cinder will be able to consume any image in
    ``compressed`` container format *that Cinder has created*.  You should
    not expect, however, for other services to be able to consume such an image
    at the present time.  Further, you should not expect Cinder to be able
    to successfully use an image in ``compressed`` format that it has not
    created itself.
issues:
  - |
    The introduction of the ``compressed`` container format in this release
    gives us the opportunity to remind you that Glance does not verify that
    the ``container_format`` image property is accurate for *any* container
    format.  It is the responsibility of the image consumer to verify the
    image data payload format and take appropriate action in the case of a
    misdescribed image.
  - |
    The intent of the ``compressed`` container format identifier introduced
    in this release is that it will be used for any compressed file archive
    format (for example, gzip or rar) that is not otherwise covered by the
    existing container format identifiers.

    The exact format of the compressed file is unspecified.  It is the
    responsibility of the consuming service to analyze the data payload and
    determine the compression format.  A particular OpenStack service may only
    support specific formats.  Thus, even if a service does support the
    ``compressed`` container format, this does not imply that the service can
    handle arbitrary compression formats.  Consult the documentation for the
    service that will consume your image for details.
  - |
    As of this release, the only service using the ``compressed`` container
    format is Cinder (Block Storage Service), when Cinder is configured to use
    compression when uploading a volume-image to Glance.  While you may expect
    that Cinder will be able to consume any image in ``compressed`` container
    format *that Cinder has created*, you should not expect Cinder to be able
    to successfully use an image in ``compressed`` format that it has not
    created itself.  Consult the `Cinder documentation
    <https://docs.openstack.org/cinder/latest>`_
    for more information.