openstack/nova
Code Issues Proposed changes

Merge "Update the cells FAQs and scheduler maintenance docs."

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Zuul 2018-04-05 23:16:22 +00:00 committed by Gerrit Code Review
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19
doc/source/admin/configuration/schedulers.rst
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@ -1252,3 +1252,22 @@ XenServer hypervisor pools to support live migration
When using the XenAPI-based hypervisor, the Compute service uses host
aggregates to manage XenServer Resource pools, which are used in supporting
live migration.
Cells considerations
~~~~~~~~~~~~~~~~~~~~
By default cells are enabled for scheduling new instances but they can be
disabled (new schedulings to the cell are blocked). This may be useful for
users while performing cell maintenance, failures or other interventions. It is
to be noted that creating pre-disabled cells and enabling/disabling existing
cells should either be followed by a restart or SIGHUP of the nova-scheduler
service for the changes to take effect.
Command-line interface
----------------------
The :command:`nova-manage` command-line client supports the cell-disable
related commands. To enable or disable a cell, use
:command:`nova-manage cell_v2 update_cell` and to create pre-disabled cells,
use :command:`nova-manage cell_v2 create_cell`. See the
:ref:`man-page-cells-v2` man page for details on command usage.

24
doc/source/user/cells.rst
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@ -617,3 +617,27 @@ FAQs
**NO**. Those options are for Cells v1 usage only and are not used at all
for Cells v2. That includes the ``nova-cells`` service - it has nothing
to do with Cells v2.
#. Can I create a cell but have it disabled from scheduling?
Yes. It is possible to create a pre-disabled cell such that it does not
become a candidate for scheduling new VMs. This can be done by running the
``nova-manage cell_v2 create_cell`` command with the ``--disabled`` option.
#. How can I disable a cell so that the new server create requests do not go to
it while I perform maintenance?
Existing cells can be disabled by running ``nova-manage cell_v2 update_cell
--cell_uuid <cell_uuid> --disable`` and can be re-enabled once the
maintenance period is over by running ``nova-manage cell_v2 update_cell
--cell_uuid <cell_uuid> --enable``
#. I disabled (or enabled) a cell using the ``nova-manage cell_v2 update_cell``
or I created a new (pre-disabled) cell(mapping) using the
``nova-manage cell_v2 create_cell`` command but the scheduler is still using
the old settings.
The cell mappings are cached in the scheduler worker so you will either need
to restart the scheduler process to refresh the cache, or send a SIGHUP
signal to the scheduler by which it will automatically refresh the cells
cache and the changes will take effect.