213 lines
7.4 KiB
ReStructuredText
213 lines
7.4 KiB
ReStructuredText
..
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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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.. _multi_stores:
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Multi Store Support
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===================
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.. note:: The Multi Store feature was introduced as EXPERIMENTAL in Rocky
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and is now fully supported in the Train release.
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Scope of this document
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----------------------
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This page describes how to enable multiple stores in glance.
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Prerequisites
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-------------
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* Glance version 17.0.0 or Later
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* Glance Store Library 0.25.0 or Later
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* Glance not using the Glance Registry
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* Available backends
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Procedure
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---------
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In this section, we discuss what configuration options are available to
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operators to enable multiple stores support.
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* in the ``[DEFAULT]`` options group:
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* ``enabled_backends`` must be set as a key:value pair where key
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represents the identifier for the store and value will be the type
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of the store. Valid values are one of ``file``, ``http``, ``rbd``,
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``swift``, ``cinder`` or ``vmware``. In order to have multiple stores
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operator can specify multiple key:value separated by comma.
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.. warning::
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The store identifier prefix ``os_glance_`` is reserved. If you
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define a store identifier with this prefix, the glance service will
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refuse to start.
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The http store type is always treated by Glance as a read-only
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store. This is indicated in the response to the ``/v2/stores/info``
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call, where an http type store will have the attribute ``read-only:
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True`` in addition to the usual ``id`` and ``description`` fields.
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.. code-block:: ini
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[DEFAULT]
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enabled_backends = fast:rbd, cheap:rbd, shared:file, reliable:file
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* in the ``[glance_store]`` options group:
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* ``default_backend`` must be set to one of the identifier which are defined
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using ``enabled_backends`` option. If ``default_backend`` is not set or if
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it is not representing one of the valid store drivers then it will prevent
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glance api service from starting.
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.. code-block:: ini
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[glance_store]
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default_backend = fast
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* For each of the store identifier defined in ``enabled_backends`` section
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operator needs to add a new config group which will define config options
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related to that particular store.
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.. code-block:: ini
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[shared]
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filesystem_store_datadir = /opt/stack/data/glance/shared_images/
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store_description = "Shared filesystem store"
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[reliable]
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filesystem_store_datadir = /opt/stack/data/glance/reliable
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store_description = "Reliable filesystem backend"
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[fast]
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store_description = "Fast rbd backend"
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rbd_store_chunk_size = 8
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rbd_store_pool = images
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rbd_store_user = admin
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rbd_store_ceph_conf = /etc/ceph/ceph.conf
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rados_connect_timeout = 0
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[cheap]
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store_description = "Cheap rbd backend"
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rbd_store_chunk_size = 8
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rbd_store_pool = images
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rbd_store_user = admin
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rbd_store_ceph_conf = /etc/ceph/ceph1.conf
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rados_connect_timeout = 0
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.. note ::
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``store_description`` is a new config option added to each store where
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operator can add meaningful description about that store. This
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description is displayed in the GET /v2/info/stores response.
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Store Configuration Issues
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Please keep the following points in mind.
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* Due to the special read only nature and characteristics of the
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http store type, configuring multiple instances of the http type
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store **is not supported**. (This constraint is not currently
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enforced in the code.)
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* Each instance of the filesystem store **must** have a different value
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for the ``filesystem_store_datadir``. (This constraint is not currently
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enforced in the code.)
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.. _reserved_stores:
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Reserved Stores
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---------------
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With the Train release, Glance is beginning a transition from its former
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reliance upon local directories for temporary data storage to the ability
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to use backend stores accessed via the glance_store library.
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In the Train release, the use of backend stores for this purpose is optional
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**unless you are using the multi store support feature**. Since you are
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reading this document, this situation most likely applies to you.
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.. note::
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Currently, only the filesystem store type is supported as a Glance
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reserved store.
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The reserved stores are not intended to be exposed to end users. Thus
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they will not appear in the response to the store discovery call, GET
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/v2/info/stores, or as values in the ``OpenStack-image-store-ids``
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response header of the image-create call.
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You do not get to select the name of a reserved store; these are defined
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by Glance and begin with the prefix ``os_glance_``. In the Train release,
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you do not get to select the store type: all reserved stores must be of
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type filesystem.
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Currently, there are two reserved stores:
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``os_glance_tasks_store``
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This store is used for the tasks engine. It replaces the use of the
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DEPRECATED configuration option ``[task]/work_dir``.
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``os_glance_staging_store``
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This store is used for the staging area for the interoperable image
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import process. It replaces the use of the DEPRECATED configuration
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option ``[DEFAULT]/node_staging_uri``.
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.. note::
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If end user wants to retrieve all the available stores using
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``CONF.enabled_backeds`` then they need to remove reserved
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stores from that list explicitly.
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Configuration
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~~~~~~~~~~~~~
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As mentioned above, you do not get to select the name or the type of
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a reserved store (though we anticipate that you will be able configure
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the store type in a future release).
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The reserved stores *must* be of type filesystem. Hence, you must
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provide configuration for them in your ``glance-api.conf`` file. You
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do this by introducing a section in ``glance-api.conf`` for each reserved
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store as follows:
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.. code-block:: ini
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[os_glance_tasks_store]
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filesystem_store_datadir = /var/lib/glance/tasks_work_dir
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[os_glance_staging_store]
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filesystem_store_datadir = /var/lib/glance/staging
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Since these are both filesystem stores (remember, you do not get a choice)
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the only option you must configure for each is the
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``filesystem_store_datadir``. Please keep the following points in mind:
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* The path for ``filesystem_store_datadir`` used for the reserved
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stores must be **different** from the path you are using for
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any filesystem store you have listed in ``enabled_backends``.
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Using the same data directory for multiple filesystem stores is
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**unsupported** and may lead to data loss.
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* The identifiers for reserved stores, that is, ``os_glance_tasks_store``
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and ``os_glance_staging_store``, must **not** be included in the
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``enabled_backends`` list.
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* The reserved stores will **not** appear in the store discovery response
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or as values in the ``OpenStack-image-store-ids`` response header of
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the image-create call.
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* The reserved stores will **not** be accepted as the value of the
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``X-Image-Meta-Store`` header on the image-data-upload call or
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the image-import call.
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