.. Copyright 2010 OpenStack, LLC 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. 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.openstack.org. 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.openstack.org/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.openstack.org/images/1', 'name': 'Ubuntu 10.04 Plain', 'type': 'kernel', 'size': '5368709120'} ...]} Notes: * 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.openstack.org/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.openstack.org/images/1', 'name': 'Ubuntu 10.04 Plain 5GB', 'type': 'kernel', 'size': '5368709120', 'store': 'swift', 'created_at': '2010-02-03 09:34:01', 'updated_at': '2010-02-03 09:34:01', 'deleted_at': '', 'status': 'available', 'is_public': True, 'properties': {'distro': 'Ubuntu 10.04 LTS'}}, ...]} Notes: * 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 it's 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 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.openstack.org/images/1 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.openstack.org/images/1 x-image-meta-name Ubuntu 10.04 Plain 5GB x-image-meta-type kernel x-image-meta-size 5368709120 x-image-meta-store swift 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-property-distro Ubuntu 10.04 LTS Notes: * 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 it's 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 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.openstack.org/images/1 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.openstack.org/images/1 x-image-meta-name Ubuntu 10.04 Plain 5GB x-image-meta-type kernel x-image-meta-size 5368709120 x-image-meta-store swift 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-property-distro Ubuntu 10.04 LTS Notes: * 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 it's 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 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.openstack.org`, we issue a `POST` request to add an image to Glance:: POST http://glance.openstack.org/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. 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` 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-type` This header is required. Valid values are one of `kernel`, `machine`, `raw`, or `ramdisk`. * `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-is_public` This header is optional. When present, Glance converts the value of the header to a boolean value, so "on, 1, true" are all true values. When true, 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-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.