deb-glance/doc/source/glanceapi.rst

The Glance REST API

Glance has a RESTful API that exposes both metadata about registered virtual machine images and the image data itself.

A host that runs the bin/glance-api service is said to be a Glance API Server.

Assume there is a Glance API server running at the URL http://glance.example.com.

Let's walk through how a user might request information from this server.

Requesting a List of Public VM Images

We want to see a list of available virtual machine images that the Glance server knows about.

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

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

Note

All images returned from the above GET request are public images

Requesting Detailed Metadata on Public VM Images

We want to see more detailed information on available virtual machine images that the Glance server knows about.

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

{'images': [
  {'uri': 'http://glance.example.com/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 images returned from the above GET request are public images

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 Returned via GET /images and GET /images/detail

Both the GET /images and GET /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 About Disk and Container Formats <formats>

• disk_format=FORMAT

  Filters images having a disk_format attribute matching FORMAT

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

• status=STATUS

  Filters images having a status attribute matching STATUS

  For more information, see 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 sort 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.

Requesting Detailed Metadata on a Specific Image

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 public 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 public 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/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/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

Retrieving a Virtual Machine Image

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 public 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 public 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/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/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.

Adding a New Virtual Machine 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/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.

Adding 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. 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, or swift

  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 optional. Valid values are one of aki, ari, ami, raw, iso, vhd, vdi, qcow2, or vmdk.

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

• x-image-meta-container_format

  This header is optional. Valid values are one of aki, ari, ami, bare, or ovf.

  For more information, see 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 specific to 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.

Updating 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: Image Statuses <statuses>

Requesting 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 public image returned, we can issue a GET request to the Glance server for http://glance.example.com/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.

Requesting 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/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.

Adding 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/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.

Removing 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/images/1/members/tenant1. This query will return a 204 ("No Content") status code.

Replacing 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/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.