openstack/nova
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Add Cells V1 -> Cells V2 step-by-step example

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This adds an example for: upgrade with Cells V1.

Change-Id: I05c48152eb66148c6f247a71f70f65d2e077bd7d
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melanie witt 2017-02-03 23:10:45 +00:00
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doc/source/cells.rst
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@ -442,6 +442,112 @@ database. This will set up a single cell Nova deployment.
so you must be sure to configure it on all of your nova-scheduler
hosts.
Upgrade with Cells V1
~~~~~~~~~~~~~~~~~~~~~
You are upgrading an existing Nova install that has Cells V1 enabled and have
compute hosts in your databases. This will set up a multiple cell Nova
deployment. At this time, it is recommended to keep Cells V1 enabled during and
after the upgrade as multiple Cells V2 cell support is not fully finished and
may not work properly in all scenarios. These upgrade steps will help ensure a
simple cutover from Cells V1 to Cells V2 in the future.
1. If you haven't already created a cell0 database in a prior release,
create a database for cell0. If you are going to pass the database
connection url on the command line in step 2, you can name the cell0
database whatever you want. If you are not going to pass the database url on
the command line in step 2, you need to name the cell0 database based on the
name of your existing Nova database: <Nova database name>_cell0. For
example, if your Nova database is named ``nova``, then your cell0 database
should be named ``nova_cell0``.
2. Run the ``map_cell0`` command to create and map cell0::
nova-manage cell_v2 map_cell0 \
--database_connection <database connection url>
The database connection url is generated based on the
``[database]/connection`` setting in the Nova configuration file if not
specified on the command line.
3. Run ``nova-manage db sync`` to populate the cell0 database with a schema.
The ``db sync`` command reads the database connection for cell0 that was
created in step 2.
4. Run the ``create_cell`` command to create cells which will contain your
compute hosts::
nova-manage cell_v2 create_cell --name <cell name> \
--transport-url <transport url for message queue> \
--database_connection <database connection url>
You will need to repeat this step for each cell in your deployment. Your
existing cell database will be re-used -- this simply informs the top-level
API database about your existing cell databases.
It is a good idea to specify a name for the new cell you create so you can
easily look up cell uuids with the ``list_cells`` command later if needed.
The transport url is taken from the ``[DEFAULT]/transport_url`` setting in
the Nova configuration file if not specified on the command line. The
database url is taken from the ``[database]/connection`` setting in the Nova
configuration file if not specified on the command line. If you are not
going to specify ``--database_connection`` and ``--transport-url`` on the
command line, be sure to specify your existing cell Nova configuration
file::
nova-manage --config-file <cell nova.conf> cell_v2 create_cell \
--name <cell name>
5. Run the ``discover_hosts`` command to map compute hosts to cells::
nova-manage cell_v2 discover_hosts --cell_uuid <cell uuid>
You will need to repeat this step for each cell in your deployment unless
you omit the ``--cell_uuid`` option. If the cell uuid is not specified on
the command line, ``discover_hosts`` will search for compute hosts in each
cell database and map them to the corresponding cell. You can use the
``list_cells`` command to look up cell uuids if you are going to specify
``--cell_uuid``.
You can also configure a periodic task to have Nova discover new hosts
automatically by setting the
``[scheduler]/discover_hosts_in_cells_interval`` to a time interval in
seconds. The periodic task is run by the nova-scheduler service, so you must
be sure to configure it on all of your nova-scheduler hosts.
6. Run the ``map_instances`` command to map instances to cells::
nova-manage cell_v2 map_instances --cell_uuid <cell uuid> \
--max-count <max count>
You will need to repeat this step for each cell in your deployment. You can
use the ``list_cells`` command to look up cell uuids.
The ``--max-count`` option can be specified if you would like to limit the
number of instances to map in a single run. If ``--max-count`` is not
specified, all instances will be mapped. Repeated runs of the command will
start from where the last run finished so it is not necessary to increase
``--max-count`` to finish. An exit code of 0 indicates that all instances
have been mapped. An exit code of 1 indicates that there are remaining
instances that need to be mapped.
.. note:: Remember: In the future, whenever you add new compute hosts, you
will need to run the ``discover_hosts`` command after starting them
to map them to a cell if you did not configure the automatic host
discovery in step 5.
Adding a new cell to an existing deployment
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To expand your deployment with a new cell, first follow the usual steps for
standing up a new Cells V1 cell. After that is finished, follow step 4 in
`Upgrade with Cells V1`_ to create a new Cells V2 cell for it. If you have
added new compute hosts for the new cell, you will also need to run the
``discover_hosts`` command after starting them to map them to the new cell if
you did not configure the automatic host discovery as described in step 5 in
`Upgrade with Cells V1`_.
References
~~~~~~~~~~