74 lines
2.3 KiB
ReStructuredText
74 lines
2.3 KiB
ReStructuredText
..
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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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Glance Architecture
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===================
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Glance is designed to be as adaptable as possible for various back-end storage
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and registry database solutions. There is a main Glance API server
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(the ``glance-api`` program) that serves as the communications hub between
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various client programs, the registry of image metadata, and the storage
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systems that actually contain the virtual machine image data.
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From a birdseye perspective, one can visualize the Glance architectural model
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like so:
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.. graphviz::
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digraph birdseye {
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node [fontsize=10 fontname="Monospace"]
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a [label="Client A"]
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b [label="Client B"]
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c [label="Client C"]
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d [label="Glance API Server"]
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e [label="Registry Server"]
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f [label="Store Adapter"]
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g [label="S3 Store"]
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h [label="Swift Store"]
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i [label="Filesystem Store"]
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j [label="HTTP Store"]
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a -> d [dir=both]
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b -> d [dir=both]
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c -> d [dir=both]
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d -> e [dir=both]
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d -> f [dir=both]
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f -> g [dir=both]
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f -> h [dir=both]
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f -> i [dir=both]
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f -> j [dir=both]
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}
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What is a Registry Server?
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==========================
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A registry server is a service that publishes image metadata for internal
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consumption by the Glance API server. The Glance registry server uses a
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SQL database for its metadata storage.
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What is a Store?
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================
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A store is a Python class that inherits from ``glance.store.Backend`` and
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conforms to that class' API for reading, writing, and deleting virtual
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machine image data.
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Glance currently ships with stores for S3, Swift, RBD, a simple filesystem store,
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and a read-only HTTP(S) store.
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Implementors are encouraged to create stores for other backends, including
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other distributed storage systems like Sheepdog.
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