..
      Copyright 2010 OpenStack Foundation
      All Rights Reserved.

      Licensed under the Apache License, Version 2.0 (the "License"); you may
      not use this file except in compliance with the License. You may obtain
      a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
      License for the specific language governing permissions and limitations
      under the License.

Using Glance's Public APIs
==========================

Glance fully implements versions 1.0, 1.1 and 2.0 of the OpenStack Images API.
The Images API specification is developed alongside Glance, but is not
considered part of the Glance project.

Authentication
--------------

Glance depends on Keystone and the OpenStack Identity API to handle
authentication of clients. You must obtain an authentication token from
Keystone using and send it along with all API requests to Glance through
the ``X-Auth-Token`` header. Glance will communicate back to Keystone to
verify the token validity and obtain your identity credentials.

See :doc:`authentication` for more information on integrating with Keystone.

Using v1.X
----------

For the purpose of examples, assume there is a Glance API server running
at the URL ``http://glance.example.com`` on the default port 80.

List Available Images
*********************

We want to see a list of available images that the authenticated user has
access to. This includes images owned by the user, images shared with the user
and public images.

We issue a ``GET`` request to ``http://glance.example.com/v1/images`` to
retrieve this list of available images. The data is returned as a JSON-encoded
mapping in the following format::

  {'images': [
    {'uri': 'http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9',
     'name': 'Ubuntu 10.04 Plain',
     'disk_format': 'vhd',
     'container_format': 'ovf',
     'size': '5368709120'}
    ...]}


List Available Images in More Detail
************************************

We want to see a more detailed list of available images that the authenticated
user has access to. This includes images owned by the user, images shared with
the user and public images.

We issue a ``GET`` request to ``http://glance.example.com/v1/images/detail`` to
retrieve this list of available images. The data is returned as a
JSON-encoded mapping in the following format::

  {'images': [
    {'uri': 'http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9',
     'name': 'Ubuntu 10.04 Plain 5GB',
     'disk_format': 'vhd',
     'container_format': 'ovf',
     'size': '5368709120',
     'checksum': 'c2e5db72bd7fd153f53ede5da5a06de3',
     'created_at': '2010-02-03 09:34:01',
     'updated_at': '2010-02-03 09:34:01',
     'deleted_at': '',
     'status': 'active',
     'is_public': true,
     'min_ram': 256,
     'min_disk': 5,
     'owner': null,
     'properties': {'distro': 'Ubuntu 10.04 LTS'}},
    ...]}

.. note::

  All timestamps returned are in UTC

  The `updated_at` timestamp is the timestamp when an image's metadata
  was last updated, not its image data, as all image data is immutable
  once stored in Glance

  The `properties` field is a mapping of free-form key/value pairs that
  have been saved with the image metadata

  The `checksum` field is an MD5 checksum of the image file data

  The `is_public` field is a boolean indicating whether the image is
  publically available

  The `min_ram` field is an integer specifying the minimum amount of
  ram needed to run this image on an instance, in megabytes

  The `min_disk` field is an integer specifying the minimum amount of
  disk space needed to run this image on an instance, in gigabytes

  The `owner` field is a string which may either be null or which will
  indicate the owner of the image

Filtering Images Lists
**********************

Both the ``GET /v1/images`` and ``GET /v1/images/detail`` requests take query
parameters that serve to filter the returned list of images. The following
list details these query parameters.

* ``name=NAME``

  Filters images having a ``name`` attribute matching ``NAME``.

* ``container_format=FORMAT``

  Filters images having a ``container_format`` attribute matching ``FORMAT``

  For more information, see :doc:`About Disk and Container Formats <formats>`

* ``disk_format=FORMAT``

  Filters images having a ``disk_format`` attribute matching ``FORMAT``

  For more information, see :doc:`About Disk and Container Formats <formats>`

* ``status=STATUS``

  Filters images having a ``status`` attribute matching ``STATUS``

  For more information, see :doc:`About Image Statuses <statuses>`

* ``size_min=BYTES``

  Filters images having a ``size`` attribute greater than or equal to ``BYTES``

* ``size_max=BYTES``

  Filters images having a ``size`` attribute less than or equal to ``BYTES``

These two resources also accept additional query parameters:

* ``sort_key=KEY``

  Results will be ordered by the specified image attribute ``KEY``. Accepted
  values include ``id``, ``name``, ``status``, ``disk_format``,
  ``container_format``, ``size``, ``created_at`` (default) and ``updated_at``.

* ``sort_dir=DIR``

  Results will be sorted in the direction ``DIR``. Accepted values are ``asc``
  for ascending or ``desc`` (default) for descending.

* ``marker=ID``

  An image identifier marker may be specified. When present only images which
  occur after the identifier ``ID`` will be listed, ie the images which have
  a `sort_key` later than that of the marker ``ID`` in the `sort_dir` direction.

* ``limit=LIMIT``

  When present the maximum number of results returned will not exceed ``LIMIT``.

.. note::

  If the specified ``LIMIT`` exceeds the operator defined limit (api_limit_max)
  then the number of results returned may be less than ``LIMIT``.

* ``is_public=PUBLIC``

  An admin user may use the `is_public` parameter to control which results are
  returned.

  When the `is_public` parameter is absent or set to `True` the following images
  will be listed: Images whose `is_public` field is `True`, owned images and
  shared images.

  When the `is_public` parameter is set to `False` the following images will be
  listed: Images (owned, shared, or non-owned) whose `is_public` field is `False`.

  When the `is_public` parameter is set to `None` all images will be listed
  irrespective of owner, shared status or the `is_public` field.

.. note::

  Use of the `is_public` parameter is restricted to admin users. For all other
  users it will be ignored.

Retrieve Image Metadata
***********************

We want to see detailed information for a specific virtual machine image
that the Glance server knows about.

We have queried the Glance server for a list of images and the
data returned includes the `uri` field for each available image. This
`uri` field value contains the exact location needed to get the metadata
for a specific image.

Continuing the example from above, in order to get metadata about the
first image returned, we can issue a ``HEAD`` request to the Glance
server for the image's URI.

We issue a ``HEAD`` request to
``http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9`` to
retrieve complete metadata for that image. The metadata is returned as a
set of HTTP headers that begin with the prefix ``x-image-meta-``. The
following shows an example of the HTTP headers returned from the above
``HEAD`` request::

  x-image-meta-uri              http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9
  x-image-meta-name             Ubuntu 10.04 Plain 5GB
  x-image-meta-disk_format      vhd
  x-image-meta-container_format ovf
  x-image-meta-size             5368709120
  x-image-meta-checksum         c2e5db72bd7fd153f53ede5da5a06de3
  x-image-meta-created_at       2010-02-03 09:34:01
  x-image-meta-updated_at       2010-02-03 09:34:01
  x-image-meta-deleted_at
  x-image-meta-status           available
  x-image-meta-is_public        true
  x-image-meta-min_ram          256
  x-image-meta-min_disk         0
  x-image-meta-owner            null
  x-image-meta-property-distro  Ubuntu 10.04 LTS

.. note::

  All timestamps returned are in UTC

  The `x-image-meta-updated_at` timestamp is the timestamp when an
  image's metadata was last updated, not its image data, as all
  image data is immutable once stored in Glance

  There may be multiple headers that begin with the prefix
  `x-image-meta-property-`.  These headers are free-form key/value pairs
  that have been saved with the image metadata. The key is the string
  after `x-image-meta-property-` and the value is the value of the header

  The response's `ETag` header will always be equal to the
  `x-image-meta-checksum` value

  The response's `x-image-meta-is_public` value is a boolean indicating
  whether the image is publically available

  The response's `x-image-meta-owner` value is a string which may either
  be null or which will indicate the owner of the image


Retrieve Raw Image Data
***********************

We want to retrieve that actual raw data for a specific virtual machine image
that the Glance server knows about.

We have queried the Glance server for a list of images and the
data returned includes the `uri` field for each available image. This
`uri` field value contains the exact location needed to get the metadata
for a specific image.

Continuing the example from above, in order to get metadata about the
first image returned, we can issue a ``HEAD`` request to the Glance
server for the image's URI.

We issue a ``GET`` request to
``http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9`` to
retrieve metadata for that image as well as the image itself encoded
into the response body.

The metadata is returned as a set of HTTP headers that begin with the
prefix ``x-image-meta-``. The following shows an example of the HTTP headers
returned from the above ``GET`` request::

  x-image-meta-uri              http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9
  x-image-meta-name             Ubuntu 10.04 Plain 5GB
  x-image-meta-disk_format      vhd
  x-image-meta-container_format ovf
  x-image-meta-size             5368709120
  x-image-meta-checksum         c2e5db72bd7fd153f53ede5da5a06de3
  x-image-meta-created_at       2010-02-03 09:34:01
  x-image-meta-updated_at       2010-02-03 09:34:01
  x-image-meta-deleted_at
  x-image-meta-status           available
  x-image-meta-is_public        true
  x-image-meta-min_ram          256
  x-image-meta-min_disk         5
  x-image-meta-owner            null
  x-image-meta-property-distro  Ubuntu 10.04 LTS

.. note::

  All timestamps returned are in UTC

  The `x-image-meta-updated_at` timestamp is the timestamp when an
  image's metadata was last updated, not its image data, as all
  image data is immutable once stored in Glance

  There may be multiple headers that begin with the prefix
  `x-image-meta-property-`.  These headers are free-form key/value pairs
  that have been saved with the image metadata. The key is the string
  after `x-image-meta-property-` and the value is the value of the header

  The response's `Content-Length` header shall be equal to the value of
  the `x-image-meta-size` header

  The response's `ETag` header will always be equal to the
  `x-image-meta-checksum` value

  The response's `x-image-meta-is_public` value is a boolean indicating
  whether the image is publically available

  The response's `x-image-meta-owner` value is a string which may either
  be null or which will indicate the owner of the image

  The image data itself will be the body of the HTTP response returned
  from the request, which will have content-type of
  `application/octet-stream`.


Add a New Image
***************

We have created a new virtual machine image in some way (created a
"golden image" or snapshotted/backed up an existing image) and we
wish to do two things:

 * Store the disk image data in Glance
 * Store metadata about this image in Glance

We can do the above two activities in a single call to the Glance API.
Assuming, like in the examples above, that a Glance API server is running
at ``glance.example.com``, we issue a ``POST`` request to add an image to
Glance::

  POST http://glance.example.com/v1/images

The metadata about the image is sent to Glance in HTTP headers. The body
of the HTTP request to the Glance API will be the MIME-encoded disk
image data.


Reserve a New Image
*******************

We can also perform the activities described in `Add a New Image`_ using two
separate calls to the Image API; the first to register the image metadata, and
the second to add the image disk data.  This is known as "reserving" an image.

The first call should be a ``POST`` to ``http://glance.example.com/v1/images``,
which will result in a new image id being registered with a status of
``queued``::

  {"image":
   {"status": "queued",
    "id": "71c675ab-d94f-49cd-a114-e12490b328d9",
    ...}
   ...}

The image data can then be added using a ``PUT`` to
``http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9``.
The image status will then be set to ``active`` by Glance.


**Image Metadata in HTTP Headers**

Glance will view as image metadata any HTTP header that it receives in a
``POST`` request where the header key is prefixed with the strings
``x-image-meta-`` and ``x-image-meta-property-``.

The list of metadata headers that Glance accepts are listed below.

* ``x-image-meta-name``

  This header is required, unless reserving an image. Its value should be the
  name of the image.

  Note that the name of an image *is not unique to a Glance node*. It
  would be an unrealistic expectation of users to know all the unique
  names of all other user's images.

* ``x-image-meta-id``

  This header is optional.

  When present, Glance will use the supplied identifier for the image.
  If the identifier already exists in that Glance node, then a
  **409 Conflict** will be returned by Glance. The value of the header
  must be a uuid in hexadecimal string notation
  (i.e. 71c675ab-d94f-49cd-a114-e12490b328d9).

  When this header is *not* present, Glance will generate an identifier
  for the image and return this identifier in the response (see below)

* ``x-image-meta-store``

  This header is optional. Valid values are one of ``file``, ``s3``, ``rbd``,
  ``swift``, ``cinder``, ``gridfs`` or ``sheepdog``

  When present, Glance will attempt to store the disk image data in the
  backing store indicated by the value of the header. If the Glance node
  does not support the backing store, Glance will return a **400 Bad Request**.

  When not present, Glance will store the disk image data in the backing
  store that is marked default. See the configuration option ``default_store``
  for more information.

* ``x-image-meta-disk_format``

  This header is required, unless reserving an image. Valid values are one of
  ``aki``, ``ari``, ``ami``, ``raw``, ``iso``, ``vhd``, ``vdi``, ``qcow2``, or
  ``vmdk``.

  For more information, see :doc:`About Disk and Container Formats <formats>`

* ``x-image-meta-container_format``

  This header is required, unless reserving an image. Valid values are one of
  ``aki``, ``ari``, ``ami``, ``bare``, or ``ovf``.

  For more information, see :doc:`About Disk and Container Formats <formats>`

* ``x-image-meta-size``

  This header is optional.

  When present, Glance assumes that the expected size of the request body
  will be the value of this header. If the length in bytes of the request
  body *does not match* the value of this header, Glance will return a
  **400 Bad Request**.

  When not present, Glance will calculate the image's size based on the size
  of the request body.

* ``x-image-meta-checksum``

  This header is optional. When present it shall be the expected **MD5**
  checksum of the image file data.

  When present, Glance will verify the checksum generated from the backend
  store when storing your image against this value and return a
  **400 Bad Request** if the values do not match.

* ``x-image-meta-is_public``

  This header is optional.

  When Glance finds the string "true" (case-insensitive), the image is marked as
  a public image, meaning that any user may view its metadata and may read
  the disk image from Glance.

  When not present, the image is assumed to be *not public* and owned by
  a user.

* ``x-image-meta-min_ram``

  This header is optional. When present it shall be the expected minimum ram
  required in megabytes to run this image on a server.

  When not present, the image is assumed to have a minimum ram requirement of 0.

* ``x-image-meta-min_disk``

  This header is optional. When present it shall be the expected minimum disk
  space required in gigabytes to run this image on a server.

  When not present, the image is assumed to have a minimum disk space requirement of 0.

* ``x-image-meta-owner``

  This header is optional and only meaningful for admins.

  Glance normally sets the owner of an image to be the tenant or user
  (depending on the "owner_is_tenant" configuration option) of the
  authenticated user issuing the request.  However, if the authenticated user
  has the Admin role, this default may be overridden by setting this header to
  null or to a string identifying the owner of the image.

* ``x-image-meta-property-*``

  When Glance receives any HTTP header whose key begins with the string prefix
  ``x-image-meta-property-``, Glance adds the key and value to a set of custom,
  free-form image properties stored with the image.  The key is the
  lower-cased string following the prefix ``x-image-meta-property-`` with dashes
  and punctuation replaced with underscores.

  For example, if the following HTTP header were sent::

    x-image-meta-property-distro  Ubuntu 10.10

  Then a key/value pair of "distro"/"Ubuntu 10.10" will be stored with the
  image in Glance.

  There is no limit on the number of free-form key/value attributes that can
  be attached to the image.  However, keep in mind that the 8K limit on the
  size of all HTTP headers sent in a request will effectively limit the number
  of image properties.


Update an Image
***************

Glance will view as image metadata any HTTP header that it receives in a
``PUT`` request where the header key is prefixed with the strings
``x-image-meta-`` and ``x-image-meta-property-``.

If an image was previously reserved, and thus is in the ``queued`` state, then
image data can be added by including it as the request body.  If the image
already as data associated with it (e.g. not in the ``queued`` state), then
including a request body will result in a **409 Conflict** exception.

On success, the ``PUT`` request will return the image metadata encoded as HTTP
headers.

See more about image statuses here: :doc:`Image Statuses <statuses>`


List Image Memberships
**********************

We want to see a list of the other system tenants (or users, if
"owner_is_tenant" is False) that may access a given virtual machine image that
the Glance server knows about.  We take the `uri` field of the image data,
append ``/members`` to it, and issue a ``GET`` request on the resulting URL.

Continuing from the example above, in order to get the memberships for the
first image returned, we can issue a ``GET`` request to the Glance
server for
``http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9/members``
.  What we will get back is JSON data such as the following::

  {'members': [
   {'member_id': 'tenant1',
    'can_share': false}
   ...]}

The `member_id` field identifies a tenant with which the image is shared.  If
that tenant is authorized to further share the image, the `can_share` field is
`true`.


List Shared Images
******************

We want to see a list of images which are shared with a given tenant.  We issue
a ``GET`` request to ``http://glance.example.com/v1/shared-images/tenant1``.  We
will get back JSON data such as the following::

  {'shared_images': [
   {'image_id': '71c675ab-d94f-49cd-a114-e12490b328d9',
    'can_share': false}
   ...]}

The `image_id` field identifies an image shared with the tenant named by
*member_id*.  If the tenant is authorized to further share the image, the
`can_share` field is `true`.


Add a Member to an Image
************************

We want to authorize a tenant to access a private image.  We issue a ``PUT``
request to
``http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9/members/tenant1``
.  With no body, this will add the membership to the image, leaving existing
memberships unmodified and defaulting new memberships to have `can_share`
set to `false`. We may also optionally attach a body of the following form::

  {'member':
   {'can_share': true}
  }

If such a body is provided, both existing and new memberships will have
`can_share` set to the provided value (either `true` or `false`).  This query
will return a 204 ("No Content") status code.


Remove a Member from an Image
*****************************

We want to revoke a tenant's right to access a private image.  We issue a
``DELETE`` request to ``http://glance.example.com/v1/images/1/members/tenant1``.
This query will return a 204 ("No Content") status code.


Replace a Membership List for an Image
**************************************

The full membership list for a given image may be replaced.  We issue a ``PUT``
request to
``http://glance.example.com/v1/images/71c675ab-d94f-49cd-a114-e12490b328d9/members``
with a body of the following form::

  {'memberships': [
   {'member_id': 'tenant1',
    'can_share': false}
   ...]}

All existing memberships which are not named in the replacement body are
removed, and those which are named have their `can_share` settings changed as
specified.  (The `can_share` setting may be omitted, which will cause that
setting to remain unchanged in the existing memberships.)  All new memberships
will be created, with `can_share` defaulting to `false` if it is not specified.


Image Membership Changes in Version 2.0
---------------------------------------

Version 2.0 of the Images API eliminates the ``can_share`` attribute of image
membership.  In the version 2.0 model, image sharing is not transitive.

In version 2.0, image members have a ``status`` attribute that reflects how the
image should be treated with respect to that image member's image list.

* The ``status`` attribute may have one of three values: ``pending``,
  ``accepted``, or ``rejected``.

* By default, only those shared images with status ``accepted`` are included in
  an image member's image-list.

* Only an image member may change his/her own membership status.

* Only an image owner may create members on an image.  The status of a newly
  created image member is ``pending``.  The image owner cannot change the
  status of a member.


Distinctions from Version 1.x API Calls
***************************************

* The response to a request to list the members of an image has changed.

  call: ``GET`` on ``/v2/images/{imageId}/members``

  response: see the JSON schema at ``/v2/schemas/members``

* The request body in the call to create an image member has changed.

  call: ``POST`` to ``/v2/images/{imageId}/members``

  request body::

  { "member": "<MEMBER_ID>" }

  where the {memberId} is the tenant ID of the image member.

  The member status of a newly created image member is ``pending``.

New API Calls
*************

* Change the status of an image member

  call: ``PUT`` on  ``/v2/images/{imageId}/members/{memberId}``

  request body::

  { "status": "<STATUS_VALUE>" }

  where <STATUS_VALUE> is one of ``pending``, ``accepted``, or ``rejected``.
  The {memberId} is the tenant ID of the image member.
