glance/doc/source/client.rst

Using Glance Programmatically with Glance's Client

While it is perfectly acceptable to issue HTTP requests directly to Glance via its RESTful API, sometimes it is better to be able to access and modify image resources via a client class that removes some of the complexity and tedium of dealing with raw HTTP requests.

Glance includes a client class for just this purpose. You can retrieve metadata about an image, change metadata about an image, remove images, and of course retrieve an image itself via this client class.

Below are some examples of using Glance's Client class. We assume that there is a Glance server running at the address glance.example.com on port 9292.

Requesting a List of Public VM Images

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

Using Glance's Client, we can do this using the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

print c.get_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.

Using Glance's Client, we can do this using the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

print c.get_images_detailed()

Filtering Images Returned via get_images() and get_images_detailed()

Both the get_images() and get_images_detailed() methods take query parameters that serve to filter the returned list of images.

When calling, simply pass an optional dictionary to the method containing the filters by which you wish to limit results, with the filter keys being one or more of the below:

• 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

Here's a quick example that will return all images less than or equal to 5G in size and in the saving status.

from glance.client import Client

c = Client("glance.example.com", 9292)

filters = {'status': 'saving', 'size_max': 5368709120}
print c.get_images_detailed(filters=filters)

Sorting Images Returned via get_images() and get_images_detailed()

Two parameters are available to sort the list of images returned by these methods.

• sort_key: KEY

  Images can be ordered by the image attribute KEY. Acceptable values: id, name, status, container_format, disk_format, created_at (default) and updated_at.

• sort_dir: DIR

  The direction of the sort may be defined by DIR. Accepted values: asc for ascending or desc (default) for descending.

The following example will return a list of images sorted alphabetically by name in ascending order.

from glance.client import Client

c = Client("glance.example.com", 9292)

print c.get_images(sort_key='name', sort_dir='asc')

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 id field for each available image. This id field value is needed to get the metadata for a specific image.

In order to get metadata for a specific image using an id, we can use the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

print c.get_image_meta("71c675ab-d94f-49cd-a114-e12490b328d9")

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.

Continuing the example from above, in order to get both the metadata about the first public image returned and its image data, we can use the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

meta, image_file = c.get_image("71c675ab-d94f-49cd-a114-e12490b328d9")

print meta

f = open('some_local_file', 'wb')
for chunk in image_file:
    f.write(chunk)
f.close()

Note

The return from Client.get_image is a tuple of (metadata, file) where metadata is a mapping of metadata about the image and file is a generator that yields chunks of image data.

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 client. Assuming, like in the examples above, that a Glance API server is running at glance.example.com, we issue a call to glance.client.Client.add_image.

The method signature is as follows:

glance.client.Client.add_image(image_meta, image_data=None)

The image_meta argument is a dictionary containing various image metadata. The keys in this dictionary map directly to the 'x-image-meta-*' headers accepted in the Glance API. Simply drop the leading 'x-image-meta-' from each header to determine what key should be used in the metadata dictionary. See the API docs <glanceapi> for a complete list of acceptable attributes. The image_data argument is the disk image data and is an optional argument.

As a complete example, the following code would add a new machine image to Glance

from glance.client import Client

c = Client("glance.example.com", 9292)

meta = {'name': 'Ubuntu 10.10 5G',
        'container_format': 'ovf',
        'disk_format': 'vhd',
        'is_public': True,
        'properties': {'distro': 'Ubuntu 10.10'}}

new_meta = c.add_image(meta, open('/path/to/image.tar.gz'))

print 'Stored image. Got identifier: %s' % new_meta['id']

Requesting Image Memberships

We want to see a list of the other system tenants that may access a given virtual machine image that the Glance server knows about.

Continuing from the example above, in order to get the memberships for the image with ID '71c675ab-d94f-49cd-a114-e12490b328d9', we can use the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

members = c.get_image_members('71c675ab-d94f-49cd-a114-e12490b328d9')

Note

The return from Client.get_image_members() is a list of dictionaries. Each dictionary has a member_id key, mapping to the tenant the image is shared with, and a can_share key, mapping to a boolean value that identifies whether the member can further share the image.

Requesting Member Images

We want to see a list of the virtual machine images a given system tenant may access.

Continuing from the example above, in order to get the images shared with 'tenant1', we can use the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

images = c.get_member_images('tenant1')

Note

The return from Client.get_member_images() is a list of dictionaries. Each dictionary has an image_id key, mapping to an image shared with the member, and a can_share key, mapping to a boolean value that identifies whether the member can further share the image.

Adding a Member To an Image

We want to authorize a tenant to access a private image.

Continuing from the example above, in order to share the image with ID '71c675ab-d94f-49cd-a114-e12490b328d9' with 'tenant1', and to allow 'tenant2' to not only access the image but to also share it with other tenants, we can use the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

c.add_member('71c675ab-d94f-49cd-a114-e12490b328d9', 'tenant1')
c.add_member('71c675ab-d94f-49cd-a114-e12490b328d9', 'tenant2', True)

Note

The Client.add_member() function takes one optional argument, the can_share value. If one is not provided and the membership already exists, its current can_share setting is left alone. If the membership does not already exist, then the can_share setting will default to False, and the membership will be created. In all other cases, existing memberships will be modified to use the specified can_share setting, and new memberships will be created with it. The return value of Client.add_member() is not significant.

Removing a Member From an Image

We want to revoke a tenant's authorization to access a private image.

Continuing from the example above, in order to revoke the access of 'tenant1' to the image with ID '71c675ab-d94f-49cd-a114-e12490b328d9', we can use the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

c.delete_member('71c675ab-d94f-49cd-a114-e12490b328d9', 'tenant1')

Note

The return value of Client.delete_member() is not significant.

Replacing a Membership List For an Image

All existing image memberships may be revoked and replaced in a single operation.

Continuing from the example above, in order to replace the membership list of the image with ID '71c675ab-d94f-49cd-a114-e12490b328d9' with two entries--the first allowing 'tenant1' to access the image, and the second allowing 'tenant2' to access and further share the image, we can use the following code

from glance.client import Client

c = Client("glance.example.com", 9292)

c.replace_members('71c675ab-d94f-49cd-a114-e12490b328d9',
                  {'member_id': 'tenant1', 'can_share': False},
                  {'member_id': 'tenant2', 'can_share': True})

Note

The first argument to Client.replace_members() is the opaque identifier of the image; the remaining arguments are dictionaries with the keys member_id (mapping to a tenant name) and can_share. Note that can_share may be omitted, in which case any existing membership for the specified member will be preserved through the replace operation.

The return value of Client.replace_members() is not significant.