openstack/glance
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[docs] Configure centralized_db cache driver

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Documented the usage of centralized_db cache driver and
migration process from SQLite to centralized_db on upgrade.

Related blueprint centralized-cache-db

Change-Id: I4404cd0cb9e7a59ea332b0ad2bac354b53c232d4
This commit is contained in:
Abhishek Kekane 2024-02-13 18:08:44 +00:00
parent 781ce28560
commit cd9d521923
1 changed files with 41 additions and 3 deletions
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44
doc/source/configuration/configuring.rst
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@ -1489,15 +1489,29 @@ One main configuration file option affects the image cache.
``glance-api`` server
``image_cache_driver=DRIVER``
Optional. Choice of ``sqlite`` or ``xattr``
Optional. Choice of ``sqlite``, ``xattr`` or ``centralized_db``
Default: ``sqlite``
Default: ``centralized_db``
The default ``sqlite`` cache driver has no special dependencies, other
The default ``centralized_db`` cache driver has no special
dependencies, other than ``worker_self_reference_url`` which needs
to be configured to store the reference of node in the database.
Earlier cache database used to be independent for each glance api
service, now with ``centralized_db`` cache driver it stores
information about the cached files at one place which is in
a central database. Old records from SQLite database will
be :ref:`migrated <sqlite-to-centralized_db-migration>` to
central database on service restart during upgrade process.
The ``sqlite`` cache driver has no special dependencies, other
than the ``python-sqlite3`` library, which is installed on virtually
all operating systems with modern versions of Python. It stores
information about the cached files in a SQLite database.
**NOTE**
In Caracal release ``sqlite`` cache driver has been deprecated and will
be removed in ``F`` development cycle.
The ``xattr`` cache driver required the ``python-xattr>=0.6.0`` library
and requires that the filesystem containing ``image_cache_dir`` have
access times tracked for all files (in other words, the noatime option
@ -1514,6 +1528,10 @@ One main configuration file option affects the image cache.
that will be used to store the cached images information. The database
is always contained in the ``image_cache_dir``.
**NOTE**
In Caracal release ``image_cache_sqlite_db`` option has been deprecated
and will be removed in ``F`` development cycle.
``image_cache_max_size=SIZE``
Optional.
@ -1527,6 +1545,26 @@ One main configuration file option affects the image cache.
designed to be run via cron on a regular basis. See more about this
executable in :ref:`Controlling the Growth of the Image Cache <image-cache>`
.. _sqlite-to-centralized_db-migration:
Migrating records from SQLite to Central database
-------------------------------------------------
In case of upgrades/updates we need to deal with migrating existing records
from SQLite database to central database. This operation will be performed
one time during service startup. If SQLite database file, configured using
``image_cache_sqlite_db`` configuration option (default ``cache.db``) is
present at service start and ``image_cache_driver`` is not set to
``centralized_db`` then we will read records from SQLite database and
insert those in newly created ``cached_images`` table in central database.
Once all records are migrated we will clear the SQLite database table
and keep the SQLite database file as it is (to be deleted by
administrator/operator later if required). Important point here is once
deployer chooses to use ``centralized_db`` and we migrate their records out
of SQLite database to central database, then we will not migrate them back
if deployer wants to revert back to ``sqlite`` driver.
Configuring Notifications
-------------------------