79ba479ada
properly with invalid or mismatched disk and container formats. Adds documentation on disk and container formats. Updates existing documentation to remove references to the now-gone type column and replaces these references with disk_format and container_format. Reworked the validates_image() method in the registry.db.api to be like what Rick was describing in reviews.
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Copyright 2010 OpenStack, LLC
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All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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Quick Guide to Getting Started with Glance
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==========================================
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Glance is a server that provides the following services:
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* Ability to store and retrieve virtual machine images
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* Ability to store and retrieve metadata about these virtual machine images
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* FUTURE: Convert a virtual machine image from one format to another
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* FUTURE: Help caching proxies such as Varnish or Squid cache machine images
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Communication with Glance occurs via a REST-like HTTP interface.
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However, Glance includes a :doc:`Client <client>` class that makes working with Glance
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easy and straightforward.
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In the Cactus release, there will be also command-line tools for
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interacting with Glance.
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Overview of Glance Architecture
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-------------------------------
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There are two main parts to Glance's architecture:
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* Glance API server
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* Glance Registry server(s)
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Glance API Server
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*****************
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The API server is the main interface for Glance. It routes requests from
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clients to registries of image metadata and to its **backend stores**, which
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are the mechanisms by which Glance actually saves incoming virtual machine
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images.
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The backend stores that Glance can work with are as follows:
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* **Swift**
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Swift is the highly-available object storage project in OpenStack. More
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information can be found about Swift `here <http://swift.openstack.org>`_.
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* **Filesystem**
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The default backend that Glance uses to store virtual machine images
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is the filesystem backend. This simple backend writes image files to the
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local filesystem.
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* **S3**
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This backend allows Glance to store virtual machine images in Amazon's
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S3 service.
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* **HTTP**
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Glance can read virtual machine images that are available via
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HTTP somewhere on the Internet. This store is **readonly**
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Glance Registry Servers
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***********************
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Glance registry servers are servers that conform to the Glance Registry API.
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Glance ships with a reference implementation of a registry server that
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complies with this API (``glance-registry``).
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For more details on Glance's architecture see :doc:`here <architecture>`. For
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more information on what a Glance registry server is, see
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:doc:`here <registries>`.
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