From 660da1e952e4d44816f430508f1039831564c116 Mon Sep 17 00:00:00 2001 From: Surya Seetharaman Date: Mon, 26 Mar 2018 11:26:11 +0200 Subject: [PATCH] Update the cells FAQs and scheduler maintenance docs. Related to blueprint cell-disable Change-Id: I020b78cc3ce035ff3466774d5d08198d89271117 --- doc/source/admin/configuration/schedulers.rst | 19 +++++++++++++++ doc/source/user/cells.rst | 24 +++++++++++++++++++ 2 files changed, 43 insertions(+) diff --git a/doc/source/admin/configuration/schedulers.rst b/doc/source/admin/configuration/schedulers.rst index 895b93b96a2b..c0a25bb79682 100644 --- a/doc/source/admin/configuration/schedulers.rst +++ b/doc/source/admin/configuration/schedulers.rst @@ -1178,3 +1178,22 @@ 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. diff --git a/doc/source/user/cells.rst b/doc/source/user/cells.rst index 5001e5be46ad..923b85116681 100644 --- a/doc/source/user/cells.rst +++ b/doc/source/user/cells.rst @@ -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 --disable`` and can be re-enabled once the + maintenance period is over by running ``nova-manage cell_v2 update_cell + --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.